Preventing Chronic Decline

On average, smokers live more than 10 years less than non-smokers. Quitting before age 40 eliminates roughly 90% of the extra death risk caused by continued smoking. The earlier you quit, the more years you gain.

Cost

It costs nothing — in fact, it saves money. A pack-a-day habit costs roughly $3–$4, which you’ll no longer spend after quitting. The hard part is getting through the withdrawal period, which usually lasts a few weeks to several months.

Benefit

One U.S. study that tracked participants without assigning them to groups found that current smokers have a life expectancy more than 10 years shorter than those who never smoked. Quitting before age 40 removes about 90% of this excess mortality risk. Quitting between ages 25–34 adds roughly 10 years to life expectancy; between 35–44, about 9 years; and between 45–54, about 6 years (as reported in the original source). Similar Chinese research from the 2010s shows that urban male smokers have a 1.65 times higher death risk than non-smokers (RR 1.65), while rural male smokers have a 1.22 times higher risk. After 10 years of sustained abstinence, this smoking-related risk nearly disappears.

Note

Secondhand smoke is deadly too: in 2004, an estimated 603,000 people worldwide died from exposure to it, accounting for roughly 1% of all global deaths that year. Even if you don’t smoke yourself, you must avoid secondhand smoke, especially to protect children. Specific quitting strategies are outlined in the following sections: Section 3 (smoking cessation medications), Section 4 (setting a quit date), Section 5 (visiting a smoking cessation clinic), and Section 6 (e-cigarettes).

Around 600,000 people worldwide die each year from secondhand smoke exposure; nearly 30% of those are children. Long‑term exposure to secondhand smoke raises the risk of hypertension, heart disease, and stroke by roughly 30% compared to non‑exposed individuals. Smoke inhaled at home is even more harmful than smoke encountered outside.

Cost

There is no monetary cost and it takes little time. The challenge is simply having the conversation with family members and guests to keep them from smoking indoors.

Benefit

In 2004, secondhand smoke caused 603,000 deaths globally — about 1.0% of all deaths worldwide, with children accounting for 28% of those fatalities. Pooled data from 57 studies show that people exposed to secondhand smoke have a 1.28‑fold higher chance of developing hypertension, a 1.39‑fold higher risk of heart disease, a 1.50‑fold higher risk of myocardial infarction, and a 1.36‑fold higher risk of stroke compared to non‑exposed individuals. The risk is greater when exposure occurs at home rather than outside.

Note

Focus on home environments first, since people spend more time there and pooled research indicates that indoor secondhand smoke is more harmful than outdoor exposure. Children bear 61% of the overall health burden caused by secondhand smoke. For personal smoking cessation, see item 1 in this section.

Relying on sheer willpower alone rarely works for most smokers. People taking varenicline are more than twice as likely to succeed compared to those taking a placebo. Those using nicotine replacement products also have a 50% higher success rate than non-medication users. Combining patches with gum or lozenges further boosts success rates by roughly 20%.

Cost

Nicotine patches and gum are over-the-counter products available at any pharmacy. A full course lasts 8–12 weeks and costs anywhere from a few hundred to over a thousand yuan. Varenicline and bupropion, on the other hand, are prescription-only drugs; you’ll need a prescription from a smoking cessation clinic or a pulmonology department. These costs are roughly offset by the money saved from buying fewer cigarettes during the same period.

Benefit

A pooled analysis of 41 randomized trials involving 17,395 participants shows that varenicline increases smoking cessation rates by 2.32 times compared to placebo (RR 2.32, 95% CI 2.15–2.51; high-certainty evidence). Varenicline also outperforms bupropion (RR 1.36, a 36% relative increase) and single-form nicotine replacement therapy (RR 1.25, a 25% relative increase). Across 133 trials with 64,640 participants, nicotine replacement products raise success rates by about 55% versus no medication at all (RR 1.55, 95% CI 1.49–1.61). Using both a patch and a fast-acting form such as gum or lozenges yields a 27% relative improvement over patch-only use (RR 1.27, 95% CI 1.17–1.37; high-certainty evidence from 16 trials with 12,169 participants).

Note

In China, these three types of medications are currently available for smoking cessation; only nicotine replacement products are sold over the counter. Common side effects of varenicline include nausea, vivid dreams, and sleep disturbances; anyone with a psychiatric history should discuss this with their doctor. A typical course of nicotine replacement therapy lasts 8–12 weeks — do not abruptly stop use but taper off gradually under medical guidance. While these medications ease withdrawal symptoms during the first few weeks, they do not eliminate cravings triggered by specific situations, so they should be used alongside the other strategies outlined in this chapter: setting a quit date (Section 4) and seeking professional help at a smoking cessation clinic (Section 5).

Many people try to cut back a little each day until they reach zero. Yet after six months, only 15.5% of those who gradually reduced their intake stayed smoke‑free, compared with 22% of people who set a quit date and stopped all at once. So it’s better to pick a date and quit completely on that day.

Cost

No cost at all. Just choose a date on the calendar and let family and coworkers know in advance.

Benefit

In the UK, 697 smokers were randomly assigned to two groups. One group quit on a predetermined date; the other cut their cigarette use by 75% during the two weeks before that date. Both groups received nursing support and used nicotine replacement therapy around the quit date. At four weeks, 49.0% (95% CI 43.8–54.2) of the “quit‑on‑date” group remained smoke‑free, versus 39.2% (34.0–44.4) of the “taper‑first” group; the relative risk was 0.80 (0.66–0.93). By six months, 22.0% (18.0–26.6) of the quit‑on‑date group stayed quit, compared with 15.5% (12.0–19.7) of the taper‑first group; the relative risk was 0.71 (0.46–0.91). Even among people who preferred tapering, the quit‑on‑date approach yielded higher success rates at four weeks (52.2% vs. 38.3%).

Note

This is a somewhat controversial topic. Cochrane previously published a review comparing these two methods; it concluded they performed similarly (RR 0.94, 95% CI 0.79–1.13, based on 10 trials with 3,760 participants). However, that review was withdrawn in 2019 and is no longer updated. The best current evidence comes from the trial described above, which favors quitting on a set date. Both groups in that trial also used nicotine replacement therapy before the quit date, an approach itself backed by evidence: early use raises success rates by roughly 25% (RR 1.25, 95% CI 1.08–1.44, based on 9 trials with 4,395 participants; moderate‑certainty evidence). Therefore, the recommended strategy is to pick a quit date, start nicotine replacement therapy two weeks beforehand, and then quit all at once on that day.

Medications and regular follow-up support from professionals are two distinct components that work best together. People who take medication while receiving dedicated follow-up have nearly twice the quit rate of those who only receive brief advice. Phone support also helps: those who proactively call the smoking cessation helpline see their success rate rise by 20–30% compared to others.

Cost

A single clinic visit costs only a few to dozens of yuan. Behavioral support typically involves 4–8 sessions lasting 30–60 minutes each, totaling under 5 hours. Calling the helpline is completely free.

Benefit

Across 52 trials involving 19,488 participants, the combination of medication and behavioral support led to a 1.83-fold higher quit rate than standard care or brief advice (RR 1.83, 95% CI 1.68–1.98; high-quality evidence). For the 43 trials conducted in medical settings, this advantage rose to 1.97-fold (95% CI 1.79–2.18). When looking at phone-based support alone: among people who called the helpline themselves, those receiving multiple follow-up calls had a 38% higher quit rate than those who only got informational materials or a single consultation (RR 1.38, 95% CI 1.19–1.61; 14 trials, 32,484 participants). For people who did not call the helpline but received scheduled phone support from researchers, the success rate was 25% higher than those without such support (RR 1.25, 95% CI 1.15–1.35; 65 trials, 41,233 participants). Both findings are supported by evidence of moderate certainty.

Note

How to find local services in China: Search “China Smoking Cessation Platform” on WeChat to access a list of local smoking cessation clinics and helplines, or call 12320 to ask about nearby options. Most of the above trials were conducted overseas, and the intensity of services at local clinics varies widely; these figures should be viewed as general guidelines only. The recommended medications are listed in Section 3 of this chapter (“Smoking cessation medications”).

Switching to nicotine‑containing e‑cigarettes helps roughly 60% more people quit smoking than nicotine patches — this finding is quite reliable. However, e‑cigarettes are not harmless; long‑term safety data remain limited. For people who have never smoked, there is absolutely no benefit to using them.

Cost

The device plus cartridges cost anywhere from a few dozen to several hundred yuan per month. In China, only tobacco‑flavored e‑cigarettes are legally sold, and only at stores holding a tobacco retail license.

Benefit

This up‑to‑date review includes 80 randomized trials involving 29,861 participants. Compared with nicotine replacement therapy, e‑cigarettes raise the quit rate by about 61% (RR 1.61, 95% CI 1.23–2.12; high‑certainty evidence based on 11 trials with 4,114 participants). In absolute terms, that translates to roughly 4 extra quitters per 100 users (range: 1–7). The rate of serious adverse events is similar between groups (risk difference 0.01, 95% CI −0.01–0.02; moderate‑certainty evidence). Compared with behavioral support alone or no support at all, e‑cigarettes improve quit rates by about 75% (RR 1.75, 95% CI 1.39–2.20; low‑certainty evidence).

Note

This topic is controversial. WHO does not recommend e‑cigarettes as a smoking‑cessation tool, citing insufficient long‑term safety data and concerns that they may attract youth to nicotine. The UK, however, includes them in its quit‑smoking services. In China, e‑cigarette sales are not completely banned but are tightly regulated under the “Administrative Measures for E‑Cigarettes.” Only tobacco‑flavored products may be sold, and only at physical stores holding a tobacco retail license; fruit‑flavored e‑cigarettes and refillable devices are prohibited. Sales through any website, online shop, or social‑media platform other than the state‑run e‑cigarette trading platform are illegal, and sales to minors are forbidden. Consequently, fruit‑flavored e‑cigarettes that are still available are sold through illicit channels outside regulatory oversight. This is also how synthetic‑cannabinoid‑laced “high‑effect” e‑cigarettes enter the market; see Section 22, Item 4 (“Do not accept unknown cartridges”). The review examined only legally regulated nicotine‑containing products; unverified e‑liquid mixtures were not included. As a first step, it is advisable to try the medication described in Item 3 of this section, which offers stronger evidence and lower cost.

People who drink more than two sugary drinks per day have about a 20% higher chance of dying during the same period compared to those who rarely drink them. Those who consume one to two per day still face a roughly 10% higher risk. Switching to sugar-free versions brings no benefit: individuals drinking two or more sugar-free drinks daily actually have a 25% higher risk of death.

Cost

There’s no cost involved, nor does it take any extra time. Switching to plain water or sugar-free tea can even save money. The real challenge is breaking the habit of drinking sweet beverages, including sugar-free ones.

Benefit

Two large U.S. studies followed large groups of people without any subgroup categorization; together they included around 118,000 participants and documented 36,000 deaths. Those drinking two or more sugary drinks daily had a 21% higher risk of death compared to those consuming less than one per month (HR 1.21). For those drinking one to two per day, the risk rose by about 14% (HR 1.14). The European EPIC study followed 450,000 people across 10 countries under similar conditions; again no subgroups were defined. Compared to those drinking less than one sugary drink per month, daily consumers of two or more sugary drinks faced an 8% higher risk (HR 1.08, 95% CI 1.01–1.16). Those drinking two or more sugar-free drinks daily had a 26% higher risk (HR 1.26, 95% CI 1.16–1.35). When all types of soft drinks were considered together, the risk increase was about 17% (HR 1.17, 95% CI 1.11–1.22).

Note

There is ongoing debate regarding sugar-free drinks. The association between sugar-free drinks and health outcomes appears even stronger than that of sugary drinks, which likely reflects reverse causality: individuals who are already overweight or have diabetes tend to switch to sugar-free versions. Therefore, we cannot claim sugar-free drinks are more harmful based on this alone. Nevertheless, this evidence clearly shows that the idea “switching to sugar-free drinks solves the problem” lacks any factual support. The safest choice remains plain water or sugar-free tea. Additionally, these studies rely solely on observational tracking rather than controlled trials; people who consume more sugary drinks often lead less healthy lifestyles overall, which may contribute to the observed higher risk figures.

People who chew betel nut have roughly a 20% higher chance of dying during the same period compared to non-chewers. Their risk of developing diabetes and metabolic syndrome is nearly 50% higher. Additional risks for oral and esophageal cancer also apply.

Cost

It costs nothing, takes no time, and saves money that would otherwise be spent on betel nut. The hard part is breaking the habit of chewing it.

Benefit

Data from 17 Asian studies involving 388,000 participants show that chewing betel nut raises overall mortality risk by about 21% relative to non-chewers (relative risk 1.21, P=0.02). This effect applies to 179,600 of those participants. The risk of diabetes rises by roughly 47% (1.47), while metabolic syndrome risk increases by about 51% (1.51). Betel nut itself is also a known risk factor for oral and esophageal cancer.

Note

The longer and more frequently one chews betel nut, the greater the risk of oral cancer becomes. After quitting, this risk gradually declines over time. Betel nut mixed with tobacco poses an even greater danger.

For people who have had a stroke or are over 60 with hypertension, switching to low‑sodium salt can lower their chance of dying within five years by about 12% and the risk of another stroke by roughly 14%.

Cost

One bag costs a few yuan more than regular salt. It’s easy to switch when you shop, adding virtually no extra time. The taste stays almost the same.

Benefit

A randomized trial conducted in rural China enrolled 20,995 participants — all stroke survivors or adults aged 60+ with hypertension — and followed them for 4.74 years. Those using low‑sodium salt had a 12% lower risk of death (RR 0.88), a 14% lower risk of stroke (RR 0.86), and a 13% lower risk of major cardiovascular events (RR 0.87) compared with the regular‑salt group. No statistically significant difference emerged between the groups regarding episodes of excessively high blood potassium levels.

Note

This finding is somewhat controversial. The PURE study only recorded long‑term outcomes without random assignment; it reported that individuals excreting less than 3 g of sodium per day faced a roughly 27% higher risk of death or cardiovascular events, while those excreting more than 7 g per day faced a 15% higher risk. According to PURE, both very low and very high sodium intake are detrimental, with moderate intake being optimal. However, the Chinese rural trial only partially replaced regular salt with low‑sodium salt, so sodium levels did not drop to the extremes examined in PURE. Moreover, the trial involved only high‑risk elderly participants; younger, healthier individuals would likely gain far less benefit. People with impaired kidney function or those taking potassium‑sparing medications should consult a physician before making this switch.

People who clean between their teeth daily have roughly a 10% lower chance of dying over the same period. For elderly individuals with no natural teeth, the risk of death is about 90% higher. Those with fewer than 20 natural teeth face roughly double the risk. Having missing teeth evaluated by a dentist protects periodontal health and eating function.

Cost

Dental floss or interdental brushes cost just a few dozen yuan per year, while professional cleanings run about 100–200 yuan each. It takes only two to three extra minutes per day. The real challenge is making flossing a daily habit.

Benefit

A Japanese study followed 9,676 participants for six years. Those who used interdental cleaning tools saw their mortality risk drop by about 11% (hazard ratio 0.89). Those who used tongue cleaners saw a 23% reduction (HR 0.77). When multiple studies of community-dwelling seniors are combined, people with no natural teeth have roughly 1.87 times the risk of death (95% CI 1.35–2.59). Those with fewer than 20 natural teeth face about 2.04 times the risk (95% CI 1.67–2.49).

Note

This topic remains debated. These studies are purely observational; individuals with poor dental health often also have poorer overall health and lower socioeconomic status. It is unclear whether poor dental health directly drives systemic disease or reflects general decline; getting dental implants or dentures has not been directly tested in trials for mortality reduction. Regardless, the cost of proper oral hygiene is very low, and missing teeth directly impair nutritional intake and masticatory function.

People who walk roughly 7,800 steps daily have a mortality risk roughly 45% lower than those walking only 3,500 steps. The same pattern holds when measured by time: those who engage in 150–300 minutes of brisk walking weekly face about 30% lower risk than inactive individuals. Beyond a certain threshold, further increases bring little extra benefit; for people over 60, 6,000–8,000 steps per day is sufficient. Meeting either step target is enough.

Cost

It costs nothing. In terms of steps, walking 60–90 minutes daily can easily be split into short bouts during commutes or errands. In terms of time, it requires just 20–45 minutes per day. The real challenge is maintaining this habit over the long term.

Benefit

Fifteen studies tracking large groups of people were combined for analysis without subgrouping. These studies included 47,471 participants and 3,013 deaths. When grouped by daily step counts, the lowest group had a median of 3,553 steps/day; the next three groups had medians of 5,801, 7,842, and 10,901 steps/day. Their mortality risks were roughly 40%, 45%, and 53% lower than the lowest group (HR 0.60, 0.55, 0.47 respectively). For those over 60, benefits plateau after reaching 6,000–8,000 steps/day; for younger adults, the plateau appears at 8,000–10,000 steps/day. Another analysis found benefits begin at around 3,867 steps/day; each additional 1,000 steps/day reduces mortality risk by roughly 15%. When measured by exercise time, individuals meeting 1–2 times the recommended weekly activity level (7.5–15 MET·h/week, equivalent to 150–300 minutes of brisk walking) had a mortality risk about 31% lower than inactive people (HR 0.69). Those below this threshold still saw a 20% reduction (HR 0.80), while those exceeding it 3–5 times saw a maximum reduction of 39% (HR 0.61). Further increases bring no additional benefit, though they pose no harm (HR 0.69 at >10 times the threshold). A final study using accelerometers showed that the top quarter of participants in terms of moderate-to-vigorous activity had a mortality risk roughly 48% lower than the bottom quarter (HR 0.52). Accelerometers are wearable devices that measure actual physical activity levels.

Note

Step counts and exercise time describe the same behavior; meeting either target suffices. The greatest benefit is seen when increasing daily steps from 4,000 to 7,000; there is no need to reach 10,000 steps. It is important to note that these studies merely track activity levels; the least active participants often include those already ill or frail, which can inflate observed risk differences. Studies relying on accelerometer measurements tend to involve shorter follow-ups and older populations, so their reported benefits may be somewhat overestimated. Nevertheless, the overall trend of greater activity leading to better outcomes remains clear.

For every 10 mmHg drop in systolic blood pressure, mortality decreases by roughly 13%, while stroke risk drops by about 27%. Each 1.0 mmol/L reduction in LDL cholesterol achieved by statins lowers mortality by roughly 10%. Those who take their medication as directed have a 30% to 45% lower risk of death compared to those who frequently miss doses. Adults should check blood lipids every 2 to 5 years before age 40, and annually starting at age 40.

Cost

Generic hypertension drugs and statins cost only a few to several dozen yuan per month. They are taken once daily, requiring minimal time. The real challenge is sticking to them long-term rather than stopping once you feel better. Checking blood lipids requires a blood draw; adults aged 65 and older have an annual free health checkup including lipid screening (see Chapter 6, Rule 18).

Benefit

Pooled data from multiple randomized controlled trials show that a 10 mmHg reduction in systolic blood pressure lowers mortality by about 13% (RR 0.87) and major cardiovascular events by roughly 20% (RR 0.80). Stroke risk drops by around 27% (RR 0.73), while heart failure risk decreases by about 28% (RR 0.72). Statins also reduce LDL cholesterol; each 1.0 mmol/L drop lowers mortality by roughly 10% (RR 0.90) and major vascular events by about 22% (RR 0.78). Observational studies further indicate that patients who adhere to prescribed treatment regimens (>=80% compliance) enjoy significantly lower mortality rates: statin adherence reduces risk by about 45% (RR 0.55), while adherence to antihypertensive therapy lowers risk by roughly 29% (RR 0.71). Official Chinese lipid guidelines and the Healthy China Action recommend regular lipid profiling: every 2 to 5 years for adults aged 20 to 39, annually for adults aged 40 and older, and every 6 months for high-risk individuals.

Note

Only individuals deemed by doctors to need medication should follow this advice; healthy people do not require medication. The figures regarding consistent medication use stem from observational data; those who stick to treatment tend to be more disciplined overall, which may inflate perceived benefits. The mortality reductions linked to blood pressure control and statins are firmly supported by randomized trials. Routine lipid screening catches silent hyperlipidemia early before coronary artery disease or stroke occurs. Primary beneficiaries are yourself and your parents.

People who regularly get less than 7 hours of sleep have roughly a 10% higher chance of dying over time. The more irregular their schedule, the greater the risk. Those with the most regular sleep patterns enjoy a 20%–50% lower mortality risk compared to those with the least regular patterns. In other words, how consistent your sleep schedule is matters more than the total number of hours you sleep.

Cost

No cost involved. You simply need to allocate time for sleep — most people achieve this by cutting back on phone usage. The real challenge is maintaining a fixed bedtime and wake‑time.

Benefit

A pooled analysis of 16 longitudinal studies — involving 1.38 million participants and 113 000 deaths — shows that short sleepers face a 12% higher risk of death (RR 1.12), while long sleepers face a 30% higher risk (RR 1.30). When sleep duration is grouped into categories, the 7‑hour bracket shows the lowest risk; each additional hour beyond 7 raises risk by about 13% (RR 1.13), and each hour less than 7 raises it by roughly 6% (RR 1.06). In the UK Biobank, wrist‑watch data from ~61 000 participants were used to rank them into five groups based on schedule regularity; the four more regular groups had a 20%–48% lower mortality risk than the least regular group. Another UK Biobank study tracked 51 562 individuals for new cardiovascular events; those with a social jet‑lag of 2 hours or more faced a 30% higher risk (HR 1.30, 95% CI 1.11–1.54), and this link persisted even among people getting a normal amount of sleep.

Note

The main issues to address are insufficient sleep and irregular schedules; there’s no need to deliberately shorten sleep time. The elevated risk seen in long sleepers is likely reversed causality — depression, chronic illness, and sleep apnea tend to cause longer sleep durations. Currently, only two longitudinal studies support the benefit of a regular schedule; both are observational and ungrouped, so they constitute B‑grade evidence on their own. For ways to recover after staying up late, see Section 38 (recovering sleep after a late night). 〔113000〕 〔61000〕 〔51562〕 〔3853〕

People who regularly play tennis, badminton, or table tennis have about half the risk of dying during the same period compared to non-players. Their risk of dying from cardiovascular causes is roughly 56% lower. Swimmers enjoy a similar benefit, with a 28% lower risk. No significant difference was observed between runners and soccer players in this data set.

Cost

The cost of court fees is typically a few dozen yuan per session. This amounts to roughly 2 hours of activity per week. The main challenge is arranging enough participants and securing a court, plus maintaining consistency week after week.

Benefit

A UK-based study tracking 80,300 participants compared those who engaged in racket sports with those who did not. The former group had a 47% lower overall mortality risk (hazard ratio 0.53, 95% CI 0.40–0.69). Their risk of cardiovascular death was 56% lower (0.44, 95% CI 0.24–0.83). Racket sports here include tennis, badminton, and table tennis. For swimmers, these figures were 0.72 and 0.59 respectively; for aerobic exercise enthusiasts they were 0.73 and 0.64, and for cyclists 0.85. No statistically significant differences were found between runners and soccer players.

Note

This finding remains somewhat controversial. Such studies are purely observational in nature. People who play racket sports tend to be healthier overall and enjoy more social interaction. The lack of difference seen among runners suggests that individual characteristics may play a role in how exercise impacts health outcomes. This does not mean running offers no benefits; a separate entry in this section examines overall exercise volume instead.

For individuals who do not exercise regularly, performing just three 1–2 minute bouts of strenuous activity each day can reduce their overall risk of death by roughly 40% compared to those who do none at all. Their risk of dying from cardiovascular causes also drops by nearly half. Such strenuous activities include stair climbing and brisk walking.

Cost

There is no cost involved, and no extra time needs to be set aside for exercise. The main challenge is remembering to climb stairs or walk briskly instead of taking shortcuts.

Benefit

A study conducted by the UK Biobank involved 25,200 participants who did not engage in regular exercise. After an average follow-up period of 6.9 years, 852 participants passed away. Those who completed three 1–2 minute bouts of strenuous activity daily saw their overall mortality risk and risk of cancer-related death drop by 38%–40%. Their risk of cardiovascular death fell by 48%–49%. Even those who accumulated just 4.4 minutes of such activity per day experienced a 26%–30% reduction in overall mortality and cancer death risk, as well as a 32%–34% drop in cardiovascular death risk.

Note

This finding is somewhat controversial. The study relied on wearable devices to accurately measure physical activity levels, which is more reliable than self-reported survey data. However, it remains an observational study without any randomized controlled trials, and the follow-up period was only 6.9 years. These results apply only to people who do not exercise regularly, and may not hold true for those who already maintain a regular exercise routine.

People who engage in 30–60 minutes of strength training each week have a 10–20% lower risk of dying during that period compared to those who don’t train at all. Training beyond this amount won’t bring any extra benefit. Combining strength training with aerobic exercise yields the best results.

Cost

Doing bodyweight squats and push-ups costs nothing. Aim for 1–2 sessions per week, each lasting 20–30 minutes. The real challenge is fitting this into your weekly schedule.

Benefit

When multiple observational studies are pooled together (without subgroup analysis), individuals who perform strength training show a 10%–17% reduction in mortality risk relative to non‑trainers. This benefit peaks at roughly 30–60 minutes of weekly training, delivering a 10%–20% risk drop; more training does not further improve outcomes. Those who also do aerobic exercise enjoy an even lower mortality risk than those who do neither type of exercise.

Note

These studies rely on follow‑up tracking, with participants self‑reporting their activity levels. The evidence supporting the notion that “excessive training can be detrimental” is quite weak, so there’s no need to cap training volume for that reason. For older adults, strength training also helps prevent falls and preserve muscle mass; those benefits are discussed in Section 1.

People who sit the longest have a 2.6 times higher chance of dying during the same period compared to those who sit the least. Sitting continuously for long stretches adds extra risk on top of that. However, if you get 60–75 minutes of moderate-intensity activity each day, this extra risk from prolonged sitting is largely offset.

Cost

It costs nothing; getting up a few times doesn’t take much time at all. The hard part is that once you sit down, you tend to lose track of time, so you need a reminder.

Benefit

One U.S. observational study used accelerometers to measure activity levels without grouping participants. It divided people into four groups based on their total daily sitting time. Those in the group with the most daily sitting time had a 2.63 times higher risk of death than those in the group with the least (HR 2.63). The study also split participants into four groups based on the longest continuous sitting period; those in the group with the longest continuous sitting time had a 1.96 times higher risk than those in the group with the shortest continuous sitting time (HR 1.96). This shows that both total daily sitting time and the length of each continuous sitting period are independently linked to mortality risk. Another meta-analysis of millions of participants also used observational data without grouping. It found that people who sat for over 8 hours a day and did little to no exercise had a 1.59 times higher risk of death compared to those who sat for less than 4 hours a day and were the most active. For the most active group, even if they sat for over 8 hours a day, their risk ratio was only 1.04 — no statistically significant difference was observed.

Note

The reliable conclusion here is that how much you move matters more than how long you sit; when you get enough exercise, the extra risk from prolonged sitting largely disappears. It’s worth noting that these studies are purely observational, so many of the people who sit the most already have underlying health issues — the “2.63 times higher risk” partly reflects this pre-existing health condition. Additionally, the same meta-analysis found that watching TV for over 3 hours a day increases risk across all activity levels; for the most active group, this risk threshold only rises to 5 hours a day.

People who eat the most ham, bacon, sausages, and similar processed meats have a roughly 20% higher chance of dying during the same period compared to those who eat the least. For every extra serving of processed meat consumed daily, that risk rises by another 20%.

Cost

It costs nothing — in fact, it saves money — and doesn’t take extra time. The hard part is simply eating less of a food you really enjoy.

Benefit

When multiple long‑term studies are pooled together (without separating participants into groups), the group eating the most processed meat faces about a 23% higher risk of death (RR 1.23) than the group eating the least. For all red meat combined, the increase is about 29% (RR 1.29). Unprocessed red meat raises the risk by roughly 10% (RR 1.10), though this difference isn’t statistically significant. Another analysis looks at daily intake: each extra daily serving of processed meat adds about a 23% higher death risk (RR 1.23), while each extra serving of red meat adds about 10% (RR 1.10).

Note

This is a contested area. The NutriRECS guidelines apply the standard GRADE evidence‑rating system and deem these studies “not very reliable.” They end up giving only a very weak recommendation: “continue eating as you do now.” The debate centers on whether the evidence is strong enough, not on the overall direction of the findings. No studies have shown any benefit from eating processed meat, and the effect of unprocessed red meat appears minimal and statistically insignificant. The key takeaway is to limit processed meat consumption.

After consuming 100 g of pure alcohol per week, the more one drinks, the earlier they tend to die. 100 g of pure alcohol is roughly equivalent to 2.5 L of beer. At age 40, people who drink 100–200 g per week lose about half a year of life expectancy; those drinking 200–350 g lose 1–2 years; and those drinking over 350 g lose 4–5 years. Overall, the healthiest amount to consume is none at all.

Cost

There is no cost at all — it saves money and time. The only difficulty is handling social pressure to drink.

Benefit

A combined analysis of 83 longitudinal studies involving 600,000 drinkers showed that the lowest mortality risk occurs at consumption levels of no more than 100 g of pure alcohol per week — roughly 2.5 L of beer at 5% alcohol content, or 300 mL of 40% alcohol spirits. At age 40, drinking 100–200 g per week shortens life expectancy by about 6 months; 200–350 g shortens it by 1–2 years; and over 350 g shortens it by 4–5 years. The Global Burden of Disease Study 2016 also concluded that zero alcohol consumption per week carries the lowest overall health risk. One adjusted analysis found that daily consumption of 1.3–24 g of alcohol was linked to a 7% lower mortality risk (RR 0.93) compared to lifelong abstainers, though this difference was not statistically significant. Daily consumption of 45–64 g raised risk by 19% (RR 1.19), and 65 g or more raised it by 35% (RR 1.35).

Note

This topic remains debated. Proponents of the “moderate drinking is beneficial” view cite a meta-analysis of 34 long-term studies showing that light drinkers have up to 17–18% lower overall mortality rates; they define “light” as up to 4 drinks per day for men and 2 for women. However, critics argue that abstainer groups often include people who stopped drinking due to illness or those with pre-existing health issues. After adjusting for such factors, the protective effect of moderate drinking disappears. Given this uncertainty, the safest conclusion is that drinking less does not meaningfully extend life, while drinking more definitely shortens it. There is no evidence supporting the idea of “starting to drink for health reasons.” Practical advice on cutting back is provided in Section 21, and guidance on quitting daily drinking is given in Section 20.

Individuals who consume large amounts of alcohol every day can suffer from withdrawal symptoms when they suddenly stop. Mild cases involve tremors, sweating, palpitations, and insomnia; severe cases may lead to seizures or delirium tremens — a life‑threatening emergency. A nationwide Norwegian health registry follow-up found that those who had experienced delirium tremens had an 8% annual mortality rate thereafter. If you wish to quit, consult a doctor first and describe exactly how much you drink each day.

Cost

Seeing a psychiatrist or addiction specialist costs just a few to several dozen yuan. In severe cases, a short hospital stay may be required.

Benefit

A 2026 clinical review notes that chronic heavy drinkers often develop withdrawal syndrome after abrupt cessation or a major reduction in intake; symptoms include tremors, autonomic hyperactivity, anxiety, insomnia, perceptual disturbances, seizures, and delirium tremens — conditions that are “common and potentially fatal” in general medical practice. Norway’s nationwide registry included 36,287 individuals diagnosed with alcohol dependence, withdrawal states, or delirium tremens between 2009 and 2015. The annual mortality rate was 8.0% in the delirium tremens group, 5.0% in the withdrawal state group, and 3.6% in the alcohol dependence group. The standardized mortality ratio for the delirium tremens group was 9.8 (95% CI 8.9–10.7), indicating that their risk of death is roughly 9.8 times higher than that of age‑matched peers.

Note

How to tell if you need help: If you drink almost every day, experience tremors, sweating, palpitations, or insomnia when you skip a day, or feel better after a morning drink, you should not attempt to quit on your own. Standard medical treatment involves using benzodiazepines to manage the acute phase and administering thiamine (vitamin B1) supplementation. The B grade reflects that the Norwegian data describe “what happens to people who have already had delirium tremens” rather than “what occurs when someone tries to quit independently”; the link between these two situations is an inference. Quitting alcohol is still advisable, but it should be done under medical supervision. For guidance on moderate drinking levels, see section 19; strategies for reducing intake are outlined in section 21.

A doctor can spend a few minutes reviewing your weekly alcohol intake, explaining the associated risks, and helping you set a realistic goal. After a year, people following this approach typically cut their weekly consumption by about 20 grams of pure alcohol — roughly equivalent to half a liter of beer. Longer consultations do not bring any additional benefits. For those already struggling with heavy drinking, two medications have been proven effective abroad: roughly one in twelve treated individuals stops drinking excessively after treatment.

Cost

No cost at all. Just count the number of drinks each day and jot it down. Asking your doctor about this during a routine visit costs nothing extra.

Benefit

Data from 34 randomized trials involving 15,197 participants show that individuals receiving brief interventions ended up drinking 20 grams less pure alcohol per week than those receiving minimal or no intervention (95% confidence interval: 12–28 grams; evidence of moderate quality). The average baseline consumption among these participants was 244 grams per week. “Brief interventions” here refer to no more than five counseling sessions totaling under 60 minutes; longer sessions provide no extra advantage. Regarding medications: 122 trials with 22,803 participants indicate that acamprosate helps one additional person per 12 treated to abstain from any drinking (95% CI: 8–26). Oral naltrexone at 50 mg daily also yields similar results — one extra abstainer per 12 patients (95% CI: 8–26).

Note

The benefit is classified as “small” because these figures reflect reductions in alcohol intake rather than lower mortality rates; per our guidelines, outcomes based on surrogate endpoints receive this rating. Most drug trials were conducted abroad, with participants already meeting criteria for alcohol dependence and receiving psychosocial support alongside medication; the reported benefits represent additional gains on top of those standard treatments. Availability and prescribing rules for these drugs in China depend on local medical practice and drug regulations; do not purchase them online without professional guidance. Those experiencing withdrawal symptoms should refer to section 20 of this chapter — do not attempt to quit abruptly on your own.

People who regularly eat nuts have roughly 20% lower mortality rates than those who don’t. Even eating nuts just once a week yields a 10% reduction in risk. The greatest benefit is seen when intake reaches a daily handful.

Cost

Consuming 28 grams per day costs roughly 200–300 yuan annually. It’s easy to fit into your routine without taking extra time.

Benefit

Two U.S.-based longitudinal studies tracked 119,000 participants over more than 3 million person-years. Compared to non-nut eaters: individuals consuming nuts less than once a week saw a 7% lower mortality risk (hazard ratio 0.93, 95% CI 0.90–0.96). Those eating nuts once a week had a 11% lower risk (0.89, 0.86–0.93). For intake of 2–4 times weekly, the reduction was 13% (0.87, 0.83–0.90); for 5–6 times weekly, 15% (0.85, 0.79–0.91). Daily consumption resulted in a 20% lower risk (0.80, 0.73–0.86).

Note

Choose unsalted, unflavored varieties. Nuts are calorie-dense, so avoid eating them in excess as a snack. Keep in mind these studies only track long-term trends — nut eaters generally maintain healthier lifestyles overall, so these figures should be interpreted with some caution.

Eating two extra servings of processed or red meat each week raises the risk of death by roughly 3% compared to normal intake. Switching to the same amount of fish or poultry eliminates this increase. Within this section, this effect is relatively minor; it’s an easy swap worth making without much effort.

Cost

There’s no extra cost or time involved. You’re simply substituting one type of meat for another — no additional purchases needed. The real challenge is adjusting your taste preferences.

Benefit

This conclusion comes from pooling data across six U.S. studies involving nearly 30,000 participants. Consuming two extra servings of processed meat weekly raised mortality risk by about 3% (hazard ratio 1.03, 95% CI 1.02–1.05). The same increase applied to unprocessed red meat (1.03, 1.01–1.05). However, replacing those servings with poultry resulted in a ratio of 0.99 (0.97–1.02), and fish gave 0.99 (0.97–1.01); neither showed any statistically significant difference.

Note

The impact of swapping just two servings per week is quite small; don’t expect a major lifespan extension from this change. When spending money on meat, choosing fish or poultry is the wiser option.

People who eat an extra 90 g of whole grains daily have a roughly 17% lower risk of dying during the same period. That amount equals about three servings. The risk continues to drop when intake rises to around 200 g per day.

Cost

Whole grain options like brown rice, oats, and whole wheat flour cost slightly more than refined varieties, and they require no extra prep time. The main challenge is getting used to their different texture.

Benefit

Pooled data from multiple observational studies (no intervention groups used) shows that adding 90 g of whole grains each day lowers mortality risk by roughly 17% (RR 0.83). This 90 g figure corresponds to three servings. The protective effect remains evident up to 210–225 g per day. Another pooled analysis found that each additional daily serving reduces risk by about 8% (RR 0.92).

Note

You do not need to replace all refined grains with whole grains — switching to half is already within the range where benefits are most pronounced. Keep in mind these studies are purely observational; people who eat more whole grains tend to be healthier overall, which may inflate the reported numbers. Results across individual studies also vary widely (I² 83%; higher values indicate greater inconsistency between study findings).

People who regularly drink tea have a roughly 15% lower chance of dying during the same period. Starting at age 50, they can expect to live 1.26 years longer on average, and 1.41 extra years without developing any cardiovascular diseases.

Cost

It costs just a few dozen to a few hundred yuan per year. Brewing a cup takes only a few minutes, so it doesn’t take up much time at all.

Benefit

A study conducted in China involving 100,900 participants, called China-PAR, tracked half of them for 7.3 years. The results showed that people with a regular tea-drinking habit had a 15% lower risk of death (hazard ratio 0.85, 95% CI 0.79–0.90, which is a reliable range). For those starting at age 50, regular tea drinkers gain 1.41 extra years free from atherosclerotic cardiovascular diseases, and 1.26 extra years of overall life expectancy.

Note

There are some limitations to this research: it is purely observational, and Chinese men who drink tea tend to smoke and drink more than average. The researchers have accounted for some of these factors, but not all. Also, avoid drinking tea that is excessively hot; refer to the section on hot drink temperatures for more details. Some people worry about mycotoxins in tea; tests on 158 batches of dark tea found aflatoxin in just 2 batches, and the amount consumed via normal tea intake stays well below internationally accepted limits. Another study examining 352 tea samples for 16 types of mycotoxins found that only ochratoxin A in dark tea exceeded the safety limit on average, but even this amount is not considered a dietary risk for regular tea drinkers. Keep tea stored in a dry place, and discard any batches that have become damp or moldy. Tea extract capsules are a different story: taking large doses of concentrated catechins at one time can damage the liver, but this risk does not apply to brewed tea at all. Therefore, all the benefits mentioned here apply only to brewed tea, not to any tea extract supplements.

People who drink three to four cups of coffee each day have a roughly 17% lower chance of dying during the same period compared to those who don’t drink coffee at all.

Cost

Making coffee at home costs just one or two yuan per day. It takes only a few minutes to brew a cup, so it doesn’t take up much time at all.

Benefit

One review combined results from 201 separate studies; all of these original studies simply recorded data without any subgroup analysis. The overall finding was that daily coffee drinkers (3–4 cups) faced a 17% lower risk of death than non-drinkers (relative risk 0.83, 95% CI 0.79–0.88 — this is a reliable range).

Note

There is some debate here: the original authors pointed out that almost all evidence comes from observational tracking studies, and they also noted that “reliable randomized controlled trials are needed to confirm a causal link.” In other words, to prove causation, participants would need to be randomly assigned to either a coffee-drinking or non-drinking group. For this benefit to apply, coffee should be consumed black; adding sugar or cream negates these positive effects. This recommendation does not apply to pregnant women, or to people suffering from arrhythmia, anxiety, or insomnia.

Consuming an extra 200 g of fruits and vegetables each day lowers the risk of death by roughly 10% during the same period. People who eat 5 servings daily have a mortality risk that is about 13% lower than those eating just 2 servings. Eating more than that does not bring any further reduction in risk.

Cost

It costs only a few to a dozen yuan per day. You also need to spend some time washing and chopping them. The real challenge is buying and eating the required amount every single day.

Benefit

When pooling data from multiple longitudinal studies (without subgroup analysis), an additional 200 g of fruits and vegetables per day is linked to a 10% drop in death risk (RR 0.90). This protective effect persists up to 800 g per day. A combined analysis of two large US longitudinal studies and 26 other studies shows that people eating 5 servings daily have a mortality risk that is about 13% lower than those eating only 2 servings (HR 0.87). The optimal mix is 2 servings of fruit and 3 servings of vegetables; any extra amount beyond that does not lower the risk further.

Note

Eating 5 servings is sufficient; there is no need to reach 10 servings, as both studies agree on this point. Keep in mind that these studies are purely observational, so confounding factors are inevitable: people who eat more vegetables and fruit tend to have higher incomes, better education, and more physical activity than others. Therefore, the reported 10% risk reduction represents the upper limit of the true effect.

People who consume the most ultra-processed foods have a roughly 20% higher risk of dying during the study period compared to those who eat the least, and a 50% higher risk of dying from cardiovascular disease. However, this evidence is rated as low certainty, so these figures should be interpreted with caution.

Cost

There’s no direct monetary cost, but you’ll need to spend time cooking or selecting minimally processed ingredients every day. The real challenge is overcoming the long-standing habit of choosing convenience over health.

Benefit

One systematic review combined data from multiple studies, even though those original studies did not group participants by ultra-processed food intake. The results showed that people eating more ultra-processed foods had a 21% higher risk of death (RR 1.21) and a 50% higher risk of cardiovascular death (RR 1.50) compared to those eating less. These findings are classified as “highly suggestive” and “convincing” respectively. Yet when assessed using the standard GRADE criteria, the overall certainty of this evidence is low or very low.

Note

There are three main points of debate here. First, the NOVA classification groups foods with vastly different nutritional profiles into the same category. Second, ultra-processed foods overlap heavily with sugary drinks and processed meat (see items 7 and 18), so it’s hard to isolate which factor is responsible for the observed effects. Third, GRADE ratings for this evidence are also low. Therefore, it’s unclear how much additional benefit this recommendation provides after following the other two. The opposing evidence comes from the same review’s low GRADE rating; no original studies have produced contradictory results to date. For now, focus on following items 7 and 18 — avoiding sugary drinks and limiting processed meat — before placing much emphasis on this recommendation.

People who cook with coal or wood face roughly a 10% higher chance of dying over the same period compared to those using electricity or gas. For those who heat their homes with coal or wood, the risk is about 14% higher. Those who have already switched to cleaner fuels have a mortality risk that is 13%–33% lower than those still relying on coal or wood.

Cost

Rural households must replace their stoves and pay higher fuel costs, resulting in an annual expense of several hundred to over a thousand yuan. This is a one-time change that doesn’t require ongoing effort. In cities, most households already use electricity or gas.

Benefit

A Chinese longitudinal study tracked 271,000 adults without cardiovascular disease, recording their health outcomes without assigning them to groups. Individuals who cooked using solid fuels such as coal or wood had a mortality risk roughly 11% higher (HR 1.11) than those using electricity or gas. Those who used solid fuels for heating faced a 14% higher risk (HR 1.14). Among people who had switched from solid fuels to cleaner alternatives, the risk dropped by 13% for cooking (HR 0.87) and by 33% for heating (HR 0.67). Separate data also show that for every 10 µg/m³ increase in long-term exposure to outdoor PM2.5, the risk of death from natural causes rises by roughly 8% (RR 1.08). Natural causes refer to deaths not resulting from accidents.

Note

These studies merely track health outcomes over time. Households that switch to cleaner fuels are often wealthier, so part of the observed 0.67-fold reduction in risk is likely linked to socioeconomic factors. Regarding outdoor PM2.5, individual actions such as relocating, wearing masks, or using air purifiers have limited impact. There are no studies evaluating air purifiers based on mortality rates, so no specific figures are provided here. 〔104〕

Drinking tea that is extremely hot raises your risk of esophageal cancer by 8 times compared to drinking lukewarm tea. Even “hot” tea doubles that risk. If you drink tea less than two minutes after pouring it, your risk is 5 times higher than if you wait at least four minutes to drink it.

Cost

There’s no monetary cost — you just need to wait two to three extra minutes each time. The hard part is resisting the urge to drink them when you’re craving them.

Benefit

In a high-risk area for esophageal cancer in northern Iran, researchers compared 300 patients with esophageal cancer to 571 healthy individuals. All results below are compared to people who drank lukewarm tea. Those who drank “hot” tea had roughly 2.07 times the risk of developing squamous cell carcinoma of the esophagus (95% CI: 1.28–3.35). For those who drank “extremely hot” tea, the risk was about 8.16 times higher (95% CI: 3.93–16.9). People who drank tea less than two minutes after pouring it had 5.41 times the risk of those who waited at least four minutes to drink it (95% CI: 2.63–11.1).

Note

The International Agency for Research on Cancer classifies hot drinks above 65°C as Group 2A carcinogens, meaning they are “probably carcinogenic to humans.” The same assessment also confirms that coffee itself is not carcinogenic. In China, high rates of esophageal cancer in regions such as Chaoshan and the Taihang Mountains are linked to the habit of drinking tea while it is still very hot.

Women who deliberately avoid sunlight can expect to live 0.6 to 2.1 years less than those who get the most sun exposure. Even non-smokers who avoid the sun tend to have lifespans similar to smokers who get plenty of sun.

Cost

No cost at all. Just a few minutes each day — on your commute or during lunch breaks is enough.

Benefit

A Swedish study followed nearly 29,500 women for 20 years. Compared to the group getting the most sun, those who avoided it ended up living 0.6 to 2.1 years less. The authors noted that “non-smoking women who avoid sunlight have life expectancies comparable to smokers in the group getting the most sun exposure.”

Note

There are some caveats: Sweden’s high latitude means limited sunlight overall, so these findings may not directly apply to China. It’s also possible that people avoiding sun tend to be less physically active or less inclined to go outdoors. Also, avoid sunburn — wear protection under strong midday sun, since excessive exposure raises skin cancer risk.

Mortality is lowest when BMI falls within 20–25. At BMI 27.5–30, risk rises by roughly 20%; at 30–35, it increases by about 45%; at 35–40, it nearly doubles. East Asian individuals are especially sensitive to excess weight — for every 5-point rise in BMI, risk climbs by roughly 40%.

Cost

There is no monetary cost. However, diet and exercise require daily time commitment. This is the most demanding guideline in the whole chapter: maintaining weight loss long-term is harder than losing it in the first place.

Benefit

This analysis combined individual data from 239 longitudinal studies (no subgrouping was performed). Only three groups remained in the final dataset: non-smokers, individuals without chronic illnesses at enrollment, and those who survived at least five years after enrollment. Results showed that mortality risk was lowest at BMI 20–25. Between 25–27.5, risk rose by about 7% (HR 1.07); at 27.5–30, it climbed by 20% (HR 1.20); at 30–35, by 45% (HR 1.45); at 35–40, by 94% (HR 1.94); and at 40–60, it was 2.76 times higher (HR 2.76). For East Asian populations, each additional 5 kg/m² of BMI above 25 raised mortality risk by roughly 39% (HR 1.39).

Note

This topic remains debated. Some researchers argue that being slightly overweight actually extends lifespan; their pooled data indicated a roughly 6% lower mortality risk for overweight individuals and 5% lower risk for those with mild obesity. The main disagreement centers on whether to exclude three specific data groups: smokers, individuals with pre-existing illnesses, and participants in the first few years after enrollment. Exclusion is recommended because severely ill patients often lose weight first. After removing these groups from the analysis of 239 studies, the elevated mortality risk associated with excess weight reappeared. It is also important to note that no randomized trials have proven that weight loss itself reduces overall mortality. The benefit figures above result from cross-sectional comparisons between people of different weights, not from direct proof that losing weight yields such reductions. Those aiming to lose weight need not obsess over meal timing; neither breakfast consumption nor the 16:8 intermittent fasting method offers any extra advantage — see Section 6, Item 26 for details.

People who eat chili peppers four or more times each week have a roughly 23% lower chance of dying during the same period compared to those who rarely consume them; their risk of cardiovascular-related death is also about one-third lower.

Cost

There are no costs or time commitments involved.

Benefit

A study conducted in Italy included 22,800 participants, with half of them followed for an average of 8.2 years. Over this period, 1,236 participants passed away. Those who ate chili peppers four or more times per week had a 23% lower risk of death relative to people who ate very little chili (hazard ratio 0.77, 95% CI 0.66–0.90). Their risk of cardiovascular-related death was also 34% lower (hazard ratio 0.66, 95% CI 0.50–0.86).

Note

There is some debate around these findings: the research was conducted in the context of a Mediterranean diet, so individuals who ate more chili peppers may have followed a diet overall more aligned with local traditional eating habits. Additionally, people suffering from gastroesophageal reflux, hemorrhoids, or irritable bowel syndrome may experience worsened symptoms from eating chili peppers, so they do not need to force themselves to consume it.

People who consume two or more servings of milk or yogurt each day have a roughly 17% lower chance of dying during the same period compared to those who do not drink any.

Cost

Only a few yuan per day, with no extra time required.

Benefit

The PURE study followed over 136,000 participants across 21 countries for an average of 9.1 years; 6,796 of them passed away. Those who ate two or more servings of dairy products daily faced a 17% lower risk of death than non-consumers (hazard ratio 0.83, 95% CI 0.72–0.96). This trend was statistically significant (P=0.0052).

Note

A key point of debate is that PURE included many participants from low- and middle-income countries; the fact that they could afford daily dairy intake suggests better socioeconomic status, which is hard to fully rule out as a confounding factor. Additionally, people with lactose intolerance can safely switch to yogurt or low-lactose milk instead of drinking regular milk.

Eating an extra half whole egg each day raises the overall mortality risk by roughly 7% in some observational models. Swapping that half egg for egg whites, fish, poultry, or nuts actually lowers the risk of death across all categories. There’s no need to cut eggs out of your diet entirely; eating up to one egg per day is completely safe.

Cost

No cost involved, and it takes no extra time.

Benefit

A U.S. study tracking 521,000 people found that 129,000 participants died over time. Those who ate an extra half whole egg daily had a 7% higher mortality risk (hazard ratio 1.07, 95% CI 1.06–1.08, a reliable range). Replacing that half egg with equal amounts of egg whites, poultry, fish, dairy, or nuts and legumes further reduces mortality risk, including for cardiovascular disease, cancer, and respiratory conditions. Large multi-cohort meta-analyses (such as Drouin-Chartier 2020 BMJ) confirm that consuming up to one egg per day shows no association with elevated cardiovascular risk.

Note

This topic remains highly debated: other long‑term studies of large populations and meta‑analyses have found no link between moderate egg consumption and mortality. The U.S. Dietary Guidelines have removed previous rigid dietary cholesterol limits. The key empirical takeaway is that eating up to one egg per day is fine; there is no scientific basis for completely eliminating eggs.

People who bathe almost daily have roughly 28% lower risk of cardiovascular events and about 46% lower risk of brain hemorrhage compared to those who bathe fewer than twice a week.

Cost

It costs a bit more in water and electricity; each bath takes about half an hour.

Benefit

A Japanese study involving 30,000 participants followed over 19 years identified 2,097 cardiovascular events. Those who bathed almost daily showed roughly 28% lower risk of cardiovascular events than those bathing no more than twice a week (hazard ratio 0.72, 95% CI 0.62–0.84). The risk of coronary heart disease was about 35% lower (0.65, 0.45–0.94), stroke risk dropped by roughly 26% (0.74, 0.62–0.87), and brain hemorrhage risk fell by about 46% (0.54, 0.40–0.73).

Note

There are some caveats: these results come from a Japanese population with a strong bathtub culture; most Chinese households lack the facilities for daily baths. Also, water should not be too hot and baths should not be excessively long. For older adults and those with existing cardiovascular or cerebrovascular conditions, very hot water and prolonged immersion can actually be dangerous — Japan sees many elderly deaths in bathtubs each year.

People who nap for less than an hour show no increase in mortality or chronic disease risk, and their mental clarity actually improves. In contrast, those who nap for over an hour face roughly a 30% higher risk of coronary heart disease, and about a 20% higher risk of diabetes and obesity. So set that alarm and wake up after half an hour. If you find yourself needing a one- or two-hour nap every day just to function, that’s a clear sign you should get a medical check-up.

Cost

Free. Just set an alarm before you nap; it requires very little willpower.

Benefit

One umbrella meta-analysis compiled data from 16 separate meta-analyses covering 244 health outcomes. An umbrella meta-analysis essentially aggregates findings from multiple existing meta-analyses. Its conclusions: individuals who nap for less than 60 minutes show no rise in overall mortality or chronic disease risk, and experience the greatest improvement in cognitive function (SMD 0.69, 95% CI 0.37–1.00—a reliable range). Naps lasting 20–30 minutes provide the biggest boost to physical performance (SMD 0.99, 95% CI 0.67–1.31). On the other hand, people who nap for over an hour face a roughly 30% higher risk of coronary heart disease, and about a 20% higher risk of diabetes and obesity. Another study used wrist-worn monitors to objectively measure naps in 1,338 adults aged 56 and older, rather than relying on self-reported questionnaires. After up to 19 years of follow-up, 926 participants had died. For every extra hour of napping, mortality risk rose by about 13% (HR 1.13, 95% CI 1.04–1.23). Each additional daily nap added roughly 7% to mortality risk (HR 1.07, 95% CI 1.02–1.13). People who napped in the morning faced a roughly 30% higher risk compared to those who napped earlier in the afternoon (HR 1.30, 95% CI 1.03–1.64).

Note

This topic remains somewhat controversial. Both of the aforementioned studies merely recorded nap duration without stratifying participants by health status. It’s quite possible that individuals who habitually nap for long periods already suffer from sleep apnea, anemia, hypothyroidism, depression, or other chronic conditions; thus it’s hard to isolate exactly how much of the observed mortality increase is directly attributable to napping itself. Two Mendelian randomization studies involving 453,000 and 541,000 participants respectively found only one consistent link: the more frequently a person naps, the slightly higher their blood pressure and waist circumference become. No causal effect on coronary heart disease or diabetes was detected. Consequently, you shouldn’t view “shortening naps” as a reliable strategy for lowering mortality. The recommendation to “seek medical evaluation” is essentially a Level C suggestion: if daytime fatigue is so severe that you need a lengthy nap, first examine your nighttime sleep quality; be sure to screen for sleep apnea if you snore or experience breathing pauses during sleep, and also run blood tests and thyroid function tests. For tips on how short naps can boost alertness, see Section 3, Item 11 (a 10‑minute nap in the afternoon works wonders). Information on optimal nighttime sleep duration can be found in Section 13 of this chapter (aim for seven hours per night).

People who get less sleep than they need and fail to make it up the following night have roughly a 15% higher risk of mortality compared to those with regular sleep patterns. Those who are severely sleep-deprived and still don’t catch up face a 42% higher risk. For people who do make up the lost sleep, no such elevated risk is observed. So, if you stay up late, go to bed early the next night.

Cost

No cost at all. Those extra hour or two of sleep you make up are exactly what you’d have wanted to get anyway.

Benefit

This meta-analysis involved 85,618 participants from the UK Biobank, with an average age of 61.8 years. Wrist-worn monitors tracked their daily sleep patterns over a median follow-up period of 8 years. The researchers first identified “sleep deficit nights” for each individual — nights when they got more than 2.5 hours less sleep than their personal sleep needs. The first night after such a deficit was labelled a “catch-up night”, and if participants got more sleep than required that night, it counted as a successful catch-up. Based on this, five distinct sleep patterns were identified. Compared to people with regular sleep schedules, those who were sleep-deprived and failed to catch up had a 15% higher all-cause mortality risk (HR 1.15, 95% CI 1.01–1.31). For those with a cumulative sleep deficit exceeding 3.5 hours and no catch-up, this risk rose to 42% (HR 1.42, 1.24–1.63). No significant risk elevation was found in either of the two groups that did make up their sleep deficit; for those who caught up after a moderate deficit, the HR was 1.12 (0.98–1.28). Among people who naturally get less sleep, those who were sleep-deprived and did not catch up had a 19% higher mortality risk (HR 1.19, 1.01–1.40), while those with severe sleep deficits and no catch-up faced a 38% higher risk (HR 1.38, 1.17–1.63). These findings were replicated in a separate US health survey involving 4,586 participants.

Note

This is an observational study with no formal grouping of participants. It is possible that people who cannot catch up on sleep are inherently busier or in poorer health, a factor this study does not fully account for. The fact that no risk elevation was detected in the two catch-up groups only means no statistically significant difference was found; their point estimates remain above 1, so catching up on sleep does not completely eliminate all risk. Therefore, if you stay up late, you should aim to make up the lost sleep as soon as possible, but this does not give you a free pass to regularly sacrifice sleep. For the purposes of this study, “catching up on sleep” refers to getting extra sleep on the first night after a deficit, and does not include waiting until the weekend to make up the total deficit. Maintaining a regular sleep schedule where you stay up on weekdays and catch up on weekends — a pattern known as social jetlag — is itself linked to cardiovascular disease; see item 13 in this section (aim to get around 7 hours of sleep per night with consistent sleep times). The recommendation to wake up at the same time every day, including on weekends (see item 2 in section 3) does not conflict with this advice: it simply encourages you to go to bed early on the night after a sleepless night, rather than sleeping in until noon the following day.

People who work night shifts develop cardiovascular disease about 13% more often than those who don’t, and cardiovascular deaths rise by roughly 27%. The longer you work nights, the worse it gets: for every additional five night shifts, cardiovascular disease risk climbs another 7%. So, when you weigh the long-term costs, it makes sense to switch shifts early on. As for cancer risk, the evidence linking night shifts to cancer is far weaker than commonly believed.

Cost

Switching jobs or changing shifts may mean a pay cut and loss of night-shift bonuses. Job hunting takes time and determination. If you factor this into your calculations when choosing a job, the cost is effectively zero.

Benefit

A pooled analysis of 23 studies — all observational, no subgroup adjustments — shows that night-shift workers face a roughly 13% higher risk of cardiovascular events (RR 1.13, 95% CI 1.10–1.16). Cardiovascular deaths rise by about 27% (RR 1.27, 1.18–1.36). Over time, each extra five night shifts adds roughly 7% to cardiovascular disease risk (RR 1.07, 1.04–1.09) and about 5% to cardiovascular mortality (RR 1.05, 1.03–1.06). Specific conditions show similar trends: coronary heart disease incidence rises by 22% (RR 1.22, 1.16–1.28) and mortality by the same amount; ischemic heart disease deaths increase by 39% (RR 1.39, 1.06–1.84); stroke mortality climbs by 49% (RR 1.49, 1.04–2.12). Stroke incidence, however, shows no significant rise (RR 1.06, 0.95–1.18).

Note

All these findings come from observational studies without subgroup adjustments. Night-shift workers naturally differ from others in smoking habits, weight, and income, and full adjustments are hard to achieve. Cancer risk evidence is weaker than popular claims suggest. A pooled analysis of 12 studies involving 12,132 breast cancer cases found only a 5% higher risk among night-shift workers (RR 1.05, 95% CI 0.96–1.14). After 20 years of night work, the risk rose to 25% (RR 1.25, 1.01–1.55), but this figure lost significance after accounting for publication bias; the link is “far from established.” Another long-term study of Chinese men over 16.1 years found no overall cancer link, though pancreatic cancer risk rose 59% (HR 1.59, 1.09–2.31) after 11–20 years of night work. Therefore, this analysis focuses on cardiovascular risk, not cancer. Not everyone must leave night shifts; you should weigh the long-term costs yourself. For those already working nights, several steps help: quit smoking (see Section 1); control blood pressure and cholesterol per medical advice (Section 12); and make up lost sleep after shifts (Section 38). Two additional strategies are worth trying: eat mainly during daylight hours, and use bright light during shifts plus near-total darkness during daytime rest to reset your circadian rhythm. Only the latter has proven effective at shifting the rhythm; ordinary indoor lighting leaves it unchanged even after six night shifts. Bright light at 7,000–12,000 lux combined with near-total darkness restores it in four days. Crucially, all three measures — bright night-time light, strict daytime darkness, and sunglasses on the way home — must be used together; skipping any one negates the effect. Both strategies affect metabolism and sleep only; no trials have shown they lower cardiovascular risk. On days off, returning to a daytime routine resets the rhythm again. Full numbers, sources, and details on how the body tracks time are in [docs/Biological clock and night shift.md](../../docs/research/Biological clock and night shift.md). [8202〕

When peanuts get damp and moldy, they produce aflatoxin, a confirmed human carcinogen that primarily harms the liver. After Guangzhou tightened regulations on small-scale oil producers, the share of local residents who regularly consumed homemade peanut oil and had abnormal liver function fell by roughly 35%. In Guangxi, pregnant women who ate homemade peanut oil faced a nearly 90% higher risk of giving birth to babies with low birth weight, and an 80% higher risk of premature delivery.

Cost

The price difference isn’t huge if you shop elsewhere. Just check whether the packaging lists a food production licence number starting with “SC”. The real challenge is convincing older family members used to buying homemade oil.

Benefit

Aflatoxin is a Group 1 carcinogen per the International Agency for Research on Cancer, meaning it definitely causes cancer, especially liver cancer. A Guangzhou study measured aflatoxin B1 levels in homemade peanut oil from small producers between 2010 and 2022. The median concentration was 1.29 μg/kg, with half of all samples falling between 0.12 and 6.58 μg/kg. After local rules for small producers took effect, toxin levels dropped by 2.865 μg/kg, then fell an additional 2.593 μg/kg each year. Concurrently, the proportion of local residents with abnormal liver function fell by 35% (PR 0.650, 95% CI 0.469–0.902). Another Guangxi study of 1,611 pregnant women found 81.7% ate homemade peanut oil; those women had a nearly 90% higher risk of bearing low birth weight babies (aOR 1.9, 95% CI 1.1–3.2) and an 80% higher risk of premature delivery (aOR 1.8, 95% CI 1.1–3.0).

Note

Both studies were observational, non-randomised studies with no control groups. The Guangzhou study tracked liver function test results rather than incidence of liver cancer or mortality. The median aflatoxin level in homemade oil was actually below China’s legal limit of 20 μg/kg for peanut oil, so risk stems from long-term consumption and occasional batches with higher concentrations. This legal limit applies to all peanut oil, but pre-packaged oil must meet production licence and factory inspection requirements, while small producers are subject to far fewer routine checks under regional regulations. The main beneficiaries of this advice are you and your family members who eat with you.

Cutting back on saturated fats like lard and butter and switching to vegetable oils lowers the risk of heart disease and stroke by roughly 17%. However, overall mortality shows no change. There is no evidence that swapping between soybean oil, corn oil, or canola oil makes any difference. Even consuming large amounts of flaxseed oil does not appear to reduce heart disease risk.

Cost

It doesn’t cost much extra. Vegetable oils are already the main choice in most households; the real challenge is breaking the habit of using lard or butter for stir‑frying and seasoning.

Benefit

A Cochrane review analyzed 15 randomized trials involving 56,675 participants, each followed for at least two years. Reducing saturated fat intake lowered the combined incidence of cardiovascular events by about 17% (RR 0.83, 0.70–0.98). Total mortality remained virtually unchanged (RR 0.96, 0.90–1.03) as did cardiovascular death (RR 0.95, 0.80–1.12). No significant difference was found between replacing saturated fats with polyunsaturated fats (the main component of soybean and corn oils) or with carbohydrates. Data on replacing them with monounsaturated fats (dominant in canola and olive oils) are too limited to draw conclusions. Another Cochrane review of 19 trials with 6,461 participants found that higher intake of omega‑6 fatty acids (linoleic acid) had no effect on overall mortality (RR 1.00, 0.88–1.12) or cardiovascular events (RR 0.97, 0.81–1.15). A third review of 86 trials involving 162,796 participants showed that increased consumption of plant‑derived omega‑3 fatty acids (found in flaxseed oil and perilla oil) had virtually no impact on overall mortality (RR 1.01, 0.84–1.20) or coronary events (RR 1.00, 0.82–1.22).

Note

Controversy: Some argue that the high omega‑6 content in soybean and corn oils promotes inflammation, so they recommend limiting or replacing these oils. The aforementioned omega‑6 study found no harmful effects, though the authors rated the evidence quality as low. The magnitude of benefit—a 17% reduction in cardiovascular events—is considered moderate, while overall mortality shows no change. Regardless of the oil type, portion control is essential; dietary guidelines suggest a daily limit of 25–30 grams of cooking oil per person.

Non-smoking Chinese women who rarely or never use a range hood while cooking face roughly twice the risk of developing lung cancer compared to those who use one regularly. Living in a kitchen with poor ventilation also raises this risk by about 50%, with the effect being most pronounced among households that burn coal.

Cost

For households already equipped with a range hood, the extra expense is just a bit more on the electricity bill. For those without one, buying and installing a unit costs several hundred to over a thousand dollars. The real challenge is remembering to turn it on every time you cook — don’t turn it off just because it makes noise.

Benefit

Ten case-control studies involving non-smoking Chinese women were pooled for analysis. In these studies, researchers compared lung cancer patients with healthy individuals, asking about past cooking habits. Overall, exposure to cooking fumes was linked to a 1.74-fold increase in lung cancer risk (95% CI 1.57–1.94). Four of these studies specifically looked at women who used no range hood while cooking; their risk was 2.11 times higher (95% CI 1.54–2.89). One Taiwanese study compared 1,302 non-smoking women with lung cancer to 1,302 healthy women, focusing on those with at least ten years of cooking experience. Women who used their range hood for more than two-thirds of those years had roughly half the risk of developing lung cancer compared to those who used it for less than a third of the time (OR 0.49, 95% CI 0.32–0.76). A Shanghai-based prospective study followed 71,000 non-smoking women from 1996 to 2009, identifying 429 cases of lung cancer. Women who reported living in a poorly ventilated kitchen had a 49% higher risk of lung cancer (HR 1.49, 95% CI 1.15–1.95). Those who had burned coal in such kitchens for over 20 years faced a 2.03-fold increase in risk (HR 2.03, 95% CI 1.35–3.05). No significant difference in risk was found between women who did and did not burn coal at all (HR 1.03, 95% CI 0.84–1.26), nor between those using different types of cooking oil.

Note

There is some debate regarding these findings: the evidence supporting regular range hood use comes largely from case-control studies. Since participants recall past habits after being diagnosed with lung cancer, they may underreport how often they used their range hoods, potentially inflating the observed risk figures. The Shanghai study showed the greatest risk increase among households burning coal in poorly ventilated kitchens; it did not provide separate risk estimates for households using only gas. For this reason, the overall evidence grade is set at B, while the benefit is considered substantial based on the roughly twofold difference in risk. Women who regularly do the cooking at home are the primary beneficiaries of this measure; see section 29 of this chapter for more information on avoiding coal and wood for cooking and heating.

Menopausal hormone therapy reduces the frequency of moderate-to-severe hot flushes by roughly 75% compared to placebo. However, it carries a small excess risk of breast cancer, deep vein thrombosis, and stroke—amounting to roughly 8 additional cases per 10,000 women annually for each condition. For women initiating therapy between ages 50 and 59, all-cause mortality does not increase. It should never be prescribed to prevent heart disease or dementia.

Cost

Requires a consultation at a gynecology or menopause specialty clinic. The clinician evaluates medical history and contraindications before prescribing appropriate regimens. Regular follow-up checkups are mandatory during therapy. The primary hurdle is overcoming unfounded fears that "all hormones immediately cause cancer," while avoiding over-the-counter anti-aging marketing claims.

Benefit

A Cochrane systematic review of 24 randomized controlled trials involving 3,329 women compared oral hormone therapy with placebo: women receiving hormone therapy experienced an approximate 75% reduction in weekly hot flushes compared to placebo (95% CI 64.3–82.3), alongside a significant reduction in symptom severity (OR 0.13, 95% CI 0.07–0.23). Women in placebo arms also experienced a 57.7% reduction in symptoms, demonstrating why controlled comparisons are critical. Adverse event risk profiles were established by the landmark U.S. Women's Health Initiative (WHI) randomized trial involving 16,608 postmenopausal women aged 50–79 with an intact uterus receiving combined estrogen plus progestin (mean follow-up 5.2 years): coronary heart disease increased by 29% (HR 1.29, 95% CI 1.02–1.63), invasive breast cancer increased by 26% (HR 1.26, 95% CI 1.00–1.59), stroke increased by 41% (HR 1.41, 95% CI 1.07–1.85), and pulmonary embolism increased 2.13-fold (HR 2.13, 95% CI 1.39–3.25). In absolute numbers, this corresponds to approximately 7 additional cases of coronary disease, 8 additional strokes, 8 additional pulmonary embolisms, and 8 additional invasive breast cancers per 10,000 women per year, alongside 6 fewer colorectal cancers and 5 fewer hip fractures. Conversely, for women with prior hysterectomy receiving estrogen alone, cumulative 13-year follow-up showed a 21% reduction in breast cancer incidence (HR 0.79, 95% CI 0.65–0.97). Across 18 years of cumulative follow-up for both trials combined, all-cause mortality did not differ between hormone therapy and placebo (HR 0.99, 95% CI 0.94–1.03). In age-stratified analyses, women initiating therapy between ages 50 and 59 experienced a 31% reduction in all-cause mortality during the intervention phase (HR 0.69, 95% CI 0.51–0.94), whereas older cohorts showed no mortality benefit (ages 60–69: HR 1.04; ages 70–79: HR 1.13); at 18-year post-intervention follow-up, the mortality difference in the 50–59 group was no longer statistically significant (HR 0.89, 95% CI 0.79–1.01). A 2017 Cochrane review focusing on women aged 50–59 noted venous thromboembolism as the only significantly elevated risk with combined therapy, with an absolute incidence under 1 in 500. In women aged 65 and older on combined therapy, dementia diagnoses rose from 9 to 11–30 cases per 1,000 women over 4 years. The U.S. Preventive Services Task Force (USPSTF) 2022 recommendation explicitly advises against using hormone therapy for the primary prevention of chronic conditions in postmenopausal persons (Grade D recommendation), finding no net clinical benefit.

Note

Controversy: WHI participants averaged 63 years of age and received standard oral conjugated equine estrogens plus medroxyprogesterone acetate; modern clinical practice typically initiates low-dose personalized regimens in women in their early 50s at the onset of severe perimenopausal symptoms. The mortality reduction observed in the 50–59 age bracket was a subgroup finding that attenuated over 18 years, meaning hormone therapy cannot be characterized as a life-extending longevity intervention. Contraindications generally include previous breast cancer, active or prior thromboembolism, high cardiovascular risk, and severe obesity, requiring individual clinical assessment. Women with an intact uterus must pair estrogen with a progestin to prevent endometrial hyperplasia and cancer; estrogen alone is reserved for individuals with prior hysterectomy. While hormone therapy reduces osteoporotic fractures, it is reserved for symptom control or cases where first-line osteoporosis drugs cannot be tolerated (see Chapter 1, Rules 39 and 40). Benefit magnitude is rated High based on the 75% reduction in severe vasomotor symptoms. Primary beneficiaries are yourself, your mother, or your partner.

Observational studies show that dog owners have an average 24% lower risk of all-cause mortality, with even stronger associations among individuals living alone following a heart attack or stroke. However, once studies fully adjust for socioeconomic status, physical activity, and baseline health, large cohorts in the UK and Norway found zero difference in mortality, and owning cats shows no association. Do not get a dog purely as a health intervention; if you already have or want one, leverage daily walks toward your step count.

Cost

Dog ownership represents a substantial, ongoing financial commitment covering food, vaccinations, parasite prevention, veterinary care, licensing, and grooming across the animal's entire lifespan. It demands daily dedicated time for walking and care arrangements during travel. The difficulty lies in mandatory daily adherence that cannot be paused when inconvenient.

Benefit

A meta-analysis pooling 10 prospective cohort studies comprising 3.84 million participants with a mean follow-up of 10.1 years reported that dog owners had a 24% lower risk of all-cause mortality (RR 0.76, 95% CI 0.67–0.86) and a 31% lower risk of cardiovascular mortality (RR 0.69, 95% CI 0.67–0.71). Among individuals with prior coronary disease, owning a dog was associated with a 65% lower mortality risk (RR 0.35, 95% CI 0.17–0.69); however, the authors noted this pooled estimate did not adjust for key lifestyle confounders. A nationwide Swedish registry study of 3.43 million adults adjusting for income, marital status, and education found that among single-person households, dog ownership was associated with a 33% lower mortality risk (HR 0.67, 95% CI 0.65–0.69), and an 11% lower risk in multi-person households (HR 0.89, 95% CI 0.87–0.91). Among Swedish post-myocardial infarction patients, single dog owners experienced a 33% lower risk of death (HR 0.67, 95% CI 0.61–0.75), and post-stroke patients had a 27% lower risk (HR 0.73, 95% CI 0.66–0.80). Conversely, an analysis of 6 British health survey cohorts comprising 59,352 adults followed for a mean of 11.5 years found that after full multivariable adjustment, dog ownership showed no association with all-cause mortality (HR 1.03, 95% CI 0.98–1.09) or cardiovascular mortality (HR 1.07, 95% CI 0.96–1.18). A Norwegian HUNT study cohort followed for a median of 18.5 years similarly revealed virtually identical mortality rates between dog owners and non-owners (HR 1.00, 95% CI 0.91–1.09), with dog owners exhibiting no higher physical activity than peers. An analysis of 34,202 Swedish twins with comprehensive lifestyle data failed to replicate the association between dog ownership and lower cardiovascular disease or death. An Australian cohort of 15,735 adults found an initial 23% lower mortality risk (OR 0.77, 95% CI 0.59–0.99) that was partially mediated by greater walking volume; owning cats, birds, or fish showed no correlation with mortality. An American Heart Association (AHA) scientific statement concluded that pet ownership, particularly dog ownership, "may be reasonable" for cardiovascular risk reduction (Class IIb, Level of Evidence B recommendation—the weakest recommendation grade), and explicitly advised against adopting, rescuing, or purchasing a pet primarily to reduce cardiovascular risk.

Note

Controversy: All available evidence consists of observational registries without randomized assignment, making reverse causality and healthy-user bias prominent (people capable of caring for a dog are often healthier, wealthier, and more mobile). When studies comprehensively adjust for lifestyle factors, the apparent survival advantage largely disappears. In another Swedish registry, dog owners actually initiated antihypertensive and lipid-lowering therapies at slightly higher rates, indicating that any real benefit is not mediated by lower baseline blood pressure or cholesterol. The practical takeaway is straightforward: if you already own a dog or plan to adopt one, integrate mandatory daily walks toward your daily step target (7,000–8,000 steps per day, as described in Chapter 2, Rule 11). Statutory leash laws, mandatory rabies vaccination, and third-party bite liability are detailed in Chapter 8, Rule 30. Techniques for elderly family members to grip leashes properly and avoid catastrophic falls are covered in Chapter 17, Rule 10. Benefit magnitude is categorized as High based on the unadjusted 24% relative reduction, though residual confounding is substantial. Primary beneficiary is yourself.

For individuals with elevated blood glucose who have not yet reached the diagnostic threshold for diabetes, eating less, moving more, and losing a modest amount of weight reduces the risk of progressing to full diabetes by 30% to 60%. In China's 30-year Da Qing Diabetes Prevention Study, lifestyle intervention participants had a roughly 25% lower risk of all-cause mortality, living an average of 1.4 years longer. However, similar trials in the US and Finland did not observe statistically significant differences in all-cause mortality.

Cost

Zero financial cost; eating less saves a little money. Accumulate at least 150 minutes of moderate-intensity activity (such as brisk walking) per week, averaging ~20 minutes daily. Reduce daily caloric intake by 400 to 500 kcal compared to baseline. The primary difficulty is lifelong consistency and preventing weight regain once lost. Retest blood glucose every six months (fasting blood glucose costs ~10–20 yuan).

Benefit

The Da Qing Diabetes Prevention Study was a clinic-randomized trial conducted in Da Qing, Heilongjiang Province, enrolling 577 adults with impaired glucose tolerance (a form of prediabetes) assigned to control or three 6-year intervention arms: diet alone, exercise alone, or combined diet plus exercise. Six-year cumulative diabetes incidence was 67.7% in controls versus 43.8% (diet), 41.1% (exercise), and 46.0% (combined). After adjusting for baseline BMI and fasting glucose, diabetes risk fell by 31%, 46%, and 42% respectively, with comparable reductions across lean and overweight subgroups (BMI cutoff 25). At 23-year follow-up, the combined intervention group had 41% lower cardiovascular mortality (HR 0.59, 95% CI 0.36–0.96), 29% lower all-cause mortality (HR 0.71, 95% CI 0.51–0.99), and 45% lower diabetes incidence (HR 0.55, 95% CI 0.40–0.76). At 30-year follow-up, median onset of diabetes was delayed by 3.96 years; composite cardiovascular events were 26% lower (HR 0.74, 95% CI 0.59–0.92), severe microvascular complications (retinopathy, nephropathy, neuropathy) were 35% lower (HR 0.65, 95% CI 0.45–0.95), cardiovascular mortality was 33% lower (HR 0.67, 95% CI 0.48–0.94), all-cause mortality was 26% lower (HR 0.74, 95% CI 0.61–0.89), and mean survival was prolonged by 1.44 years (95% CI 0.20–2.68). In the U.S. Diabetes Prevention Program (DPP) trial of 3,234 adults with prediabetes, the intensive lifestyle arm targeted >=7% weight loss and >=150 min/week physical activity: over a mean 2.8-year period, diabetes incidence fell by 58% (95% CI 48%–66%) compared to placebo, while metformin reduced incidence by 31% (95% CI 17%–43%). Over 15-year follow-up, lifestyle intervention maintained a 27% diabetes reduction (HR 0.73), though between-group divergence narrowed. At 21-year median follow-up, all-cause mortality (HR 1.02, 95% CI 0.81–1.28) and cardiovascular mortality (HR 1.18, 95% CI 0.77–1.81) showed no significant differences compared to controls. In the Finnish Diabetes Prevention Study (DPS) of 522 overweight adults with impaired glucose tolerance, lifestyle intervention reduced 4-year cumulative diabetes incidence by 58% (11% vs 23%), maintaining a 43% reduction at median 7-year follow-up; at 10.6 years, all-cause mortality showed no significant difference (HR 0.57, 95% CI 0.21–1.58). The Healthy China Action defines prediabetes as fasting plasma glucose 6.1 to 6.9 mmol/L and/or 2-hour post-load glucose 7.8 to 11.0 mmol/L, recommending overweight/obese individuals reduce BMI toward 24 or lose >=7% of body weight, cut daily caloric intake by 400–500 kcal, engage in >=150 min/week moderate-intensity exercise, and recheck fasting or 2-hour postprandial blood glucose every 6 months.

Note

Controverted regarding mortality endpoints. All three major trials conclusively demonstrate reduced and delayed diabetes incidence; however, a statistically significant reduction in all-cause mortality was observed only in the Da Qing trial (which enrolled 577 participants, originally powered for diabetes incidence rather than mortality). In the U.S. DPP, once the randomized phase concluded, all arms including placebo were offered group lifestyle classes. In the Finnish DPS, statistical power for subtle mortality differences was limited. Therefore, delaying diabetes progression is firmly proven, while mortality extension remains an open question. Participants in the U.S. and Finnish trials had baseline BMI >30, whereas Da Qing participants averaged BMI 25.7, with notable benefits even in participants with minimal weight loss, suggesting dietary composition and physical movement drive benefits independently of mass reduction alone. Start by eliminating sugary drinks (Chapter 2, Rule 7). Activity targets are detailed in Chapter 2, Rule 11 (7,000–8,000 steps daily). BMI targets are outlined in Chapter 2, Rule 32 (BMI 20–25). Screening thresholds are described in Chapter 1, Rule 8 (fasting blood glucose screening). Metformin also delays diabetes onset but is less effective than lifestyle modification; its initiation requires medical prescription. Benefit magnitude is categorized as High based on the 26% reduction in all-cause mortality in the Da Qing trial. Primary beneficiary is yourself.

Moldy peanuts and corn can produce aflatoxins, potent chemical carcinogens that cause liver cancer. In a long-term Shanghai prospective cohort, individuals with detectable urinary aflatoxin biomarkers had roughly 3.4 times the risk of developing liver cancer compared to those without detectable toxins. For individuals who also carry hepatitis B, having both risk factors increased liver cancer risk to roughly 59 times that of individuals with neither. Aflatoxins are extremely heat-stable and cannot be destroyed by standard boiling, roasting, or frying.

Cost

Discarding a spoiled bag of peanuts, nuts, or grain costs a few to several dozen yuan. Store dry goods in cool, well-ventilated, dry conditions, buy smaller packaging, and avoid overstocking. The main challenge is overcoming reluctance to waste food, particularly among elder family members.

Benefit

Aflatoxins are classified as Group 1 human carcinogens by the International Agency for Research on Cancer (IARC), specifically causing hepatocellular carcinoma. They proliferate most readily on peanuts, maize, and tree nuts, and are heat-resistant against standard boiling, baking, and frying. In a prospective cohort study tracking 18,244 middle-aged men in Shanghai initiated in 1986 with baseline urine biospecimens (~70,000 person-years of follow-up), 55 incident liver cancer cases occurred. Comparing 50 cases against 267 matched controls, individuals with detectable urinary aflatoxin biomarkers had 3.4 times the odds of liver cancer (relative risk [RR] 3.4, 95% CI 1.1–10.0). Positive hepatitis B surface antigen (HBsAg) was associated with 7.3-fold risk (RR 7.3, 95% CI 2.2–24.4). Individuals positive for both biomarkers had 59.4-fold higher odds (RR 59.4, 95% CI 16.6–212.0) compared to those negative for both. In earlier multivariable analyses adjusting for hepatitis B, smoking, alcohol, and education, aflatoxin exposure retained a 3.8-fold elevation in risk (95% CI 1.2–12.2). In Qidong, Jiangsu Province—historically a high-incidence liver cancer cluster—the dietary staple shifted from locally stored maize to regional rice in the 1980s: median serum aflatoxin-albumin adducts in residents dropped from 19.3 pg/mg in 1989 to undetectable levels (<0.5 pg/mg) by 2009. Concurrently, liver cancer mortality among residents aged under 35 born across successive cohorts dropped by more than 50%, preceding widespread infant hepatitis B vaccination. Researchers estimated that approximately 65% of the mortality decline was attributable to reduced dietary aflatoxin exposure, with 83% of the averted deaths occurring among chronic HBV carriers. Global risk models estimate that an equivalent aflatoxin dose exhibits roughly 30-fold greater carcinogenic potency in hepatitis B carriers than in non-carriers.

Note

Figures in the Benefit section assess the association between measured internal biomarker exposure and liver cancer; no clinical trial randomizes households to discard versus retain moldy foods. Baseline urine was collected only once in the Shanghai cohort. In Qidong, serum adducts became undetectable by 2009 following dietary shifts. The magnitude of benefit is rated Moderate because modern domestic grain storage conditions are vastly improved compared to historical rural baselines, reducing baseline exposure. Why discard the entire bag: Public health agencies advise that once opened nuts or grains show musty off-odors or visible mold, invisible microscopic fungal hyphae and airborne spores permeate the container; shaking the bag disperses toxic spores throughout the batch. The USDA food safety directives specify that peanut butter, legumes, nuts, cooked pasta, and bread with any visible mold must be discarded completely. Only firm, low-moisture produce (such as cabbage, bell peppers, or carrots) can be salvaged by cutting away at least 2.5 cm around mold spots. If you bite into a nut that tastes bitter or moldy, spit it out immediately and rinse your mouth thoroughly. Hepatitis B carriers face amplified synergistic risk; if you have not checked your HBV status, see Chapter 1, Rule 14. Avoiding unrefined small-workshop peanut oils is detailed in Chapter 2, Rule 40. Unspoiled nuts remain highly beneficial, as described in Chapter 2, Rule 22. Primary beneficiaries are yourself and family members sharing meals.

Consuming raw or undercooked freshwater fish and shrimp can transmit Clonorchis sinensis (the Chinese liver fluke). It is an established biological carcinogen; infected individuals face roughly 4 to 5 times the risk of developing cholangiocarcinoma (bile duct cancer) compared to uninfected peers. Condiments like vinegar, alcohol, and wasabi do not reliably kill liver fluke larvae. Once diagnosed, a two-day course of prescription anthelmintic medication cures over 90% of infections.

Cost

Avoiding raw freshwater fish costs nothing; the difficulty is breaking long-standing regional dietary customs and declining dishes during social dinners. If you have eaten freshwater sashimi in the past, a hospital stool microscopy test for fluke eggs costs a few dozen yuan. If infected, physician-prescribed praziquantel is taken over 1 to 2 days.

Benefit

Clonorchis sinensis was evaluated in 2009 by the WHO International Agency for Research on Cancer (IARC) and classified as a Group 1 biological carcinogen causing cholangiocarcinoma (upgraded from Group 2A in 1994). A comprehensive meta-analysis of risk factors found that liver fluke infection was associated with a 4.8-fold increase in cholangiocarcinoma risk (relative risk 4.8, 95% CI 2.8–8.4), surpassing the relative risks of hepatitis B (2.6) and hepatitis C (1.8). Another systematic review pooling 36 studies reported odds ratios for cholangiocarcinoma of 4.37 (95% CI 2.84–6.72) in case-control studies and a relative risk of 10.43 (95% CI 2.90–37.47) in cohort studies. Infection was also associated with marked elevations in cholangitis and cholecystitis (RR 7.80), gallstones (RR 2.42), and hepatocellular carcinoma (OR 4.69). National epidemiological surveys in China (2014–2015) estimated an overall infection prevalence of 0.47% (~6 million people), with rates exceeding 1% concentrated in Guangdong, Guangxi, Heilongjiang, and Jilin provinces. Spatial modeling based on surveillance from 2016 to 2021 estimated ~9.46 million infections nationwide in 2020, with regional prevalences reaching ~8.92% in Guangxi and ~2.99% in Guangdong. Baseline surveillance data in 15 national departmental action plans (2024–2030) confirmed baseline infection rates of 8.75% in Guangxi, 4.38% in Jilin, 3.16% in Heilongjiang, and 2.95% in Guangdong. China National Center for Food Safety Risk Assessment warnings emphasize that soaking raw fish in liquor, vinegar, mustard, or wasabi cannot kill encysted metacercariae. Effective destruction requires continuous freezing below -20°C for at least 7 days, or cooking until internal food temperature exceeds 70°C for over 10 minutes. Marinated and cold-smoked freshwater fish also remain infectious. For medical treatment, a 2022 network meta-analysis of 26 trials comprising 3,340 participants demonstrated that the WHO-recommended oral praziquantel regimen (25 mg/kg three times daily for 2 days) achieved an estimated cure rate of 98.5% (95% CI 85.4%–99.9%) against Clonorchis sinensis.

Note

Risk estimates derive from observational case-control and prospective registries rather than randomized controlled trials. Cholangiocarcinoma is relatively rare in the absolute population, meaning that despite elevated relative risk, absolute risk remains modest for individuals outside high-endemic culinary regions. Grade B is assigned. Adult liver flukes can survive inside the human bile duct system for 20 to 30 years; mild chronic infections often produce zero symptoms, so individuals with regular raw freshwater fish exposure should not wait for symptoms before testing. Stool microscopy for ova provides definitive diagnosis; liver ultrasound, CT, and serology are supportive. Praziquantel dosing must be determined by a physician based on body weight and infection severity; in areas where cysticercosis is co-endemic, detailed medical history is required before high-dose therapy to avoid neurological adverse events. Cured individuals can be reinfected if they continue eating raw freshwater fish. Always use separate knives and chopping boards for raw seafood versus cooked foods. Marine sashimi carries different parasites (such as Anisakis larvae). Pregnant women, young children, and older adults should strictly avoid raw seafood. Hepatitis B and C also induce liver malignancy, detailed in Chapter 1, Rule 14, and Chapter 1, Rule 45. Primary beneficiaries are yourself and dining companions.