The biggest longevity myths, fact-checked

Myth 1: Longevity is mostly determined by genetics

The intuitive logic: centenarians often have long-lived parents; age-related diseases cluster in families. The evidence disagrees with genetic determinism. A landmark 2018 analysis of genealogical data from Ancestry.com — over 400 million individuals — found that the heritability of lifespan is approximately 16%, far lower than previous estimates of 25–30%. The authors suggest longevity is influenced more by shared environments and lifestyle choices than shared genes. A 2019 Nature Medicine follow-up confirmed the pattern in independent datasets.

This is not to say genetics is irrelevant. APOE4 genotype meaningfully increases Alzheimer's risk. FOXO3A variants are overrepresented in supercentenarians. But genetics sets the range; lifestyle choices determine where within that range an individual lands. The modifiable risk factors for the leading causes of premature death — cardiovascular disease, type 2 diabetes, certain cancers — account for the majority of attributable risk.

Myth 2: Supplements are the primary lever in longevity

The supplement industry generates approximately US$180 billion annually and has successfully positioned supplementation as the primary action people should take for longevity. The evidence hierarchy tells a different story. The effect sizes for lifestyle modifications — sleep quality, aerobic fitness, resistance training, dietary quality — dwarf those of most supplements in RCT data. A fit, well-sleeping person with a poor supplement stack will age better than a sedentary, sleep-deprived person with an optimal supplement stack.

This does not mean supplements are worthless — omega-3s, vitamin D, magnesium, and creatine all have meaningful evidence. But the return on investment from addressing foundational lifestyle factors is vastly higher than adding supplements to an already-adequate protocol. The biohacking community's emphasis on exotic compounds obscures the fact that the most impactful longevity interventions are unsexy, free, and already known.

Myth 3: Eating less (caloric restriction) is always better for longevity

Caloric restriction (CR) does extend lifespan in model organisms and produces beneficial metabolic effects in humans (as shown in the CALERIE trial). However, the picture is substantially more complicated in real human populations. Excessive caloric restriction in older adults accelerates lean mass loss, impairs immune function, and increases fracture risk. A 2022 NEJM analysis confirmed that frailty — a condition characterised by sarcopenia, slow gait, and low energy — is a stronger predictor of mortality in older adults than obesity.

The nuance: in younger, overweight adults, caloric restriction with preserved protein intake is likely beneficial. In adults over 60, protein adequacy (1.2–2.0 g/kg/day) and resistance training take priority over caloric restriction. The goal is not the lowest possible caloric intake; it is the best possible body composition with adequate energy for function and repair.

Myth 4: You need to optimise sleep to exactly 8 hours

The evidence strongly supports 7–9 hours as the optimal range for most adults. But the emphasis on hitting exactly 8 hours misses what the data actually shows. The 2024 UK Biobank study (Windred et al., 60,977 participants) found that sleep regularity — consistency of timing — was a stronger predictor of mortality than sleep duration. A person sleeping 7 hours at the same time every night has better health outcomes than a person averaging 8 hours with variable timing.

Additionally, sleep architecture matters. The quality of slow-wave sleep and REM sleep — not just total duration — determines the restorative value. Alcohol, for example, reliably increases total sleep time while suppressing REM, producing a net negative effect. The goal is consistent, uninterrupted sleep at a regular time — not tracking a specific duration.

Myth 5: NAD+ supplements will reverse ageing

NAD+ precursors (NMN and NR) have a genuine and interesting evidence base — but the marketing claims substantially outrun the science. The established facts: oral NMN and NR reliably increase circulating NAD+ in humans. Animal studies show NAD+ restoration reverses multiple features of ageing in mice. The uncertain facts: whether restoring NAD+ in humans produces meaningful downstream clinical benefits in non-deficient, otherwise healthy adults remains unproven. The 2024 meta-analysis of 12 NMN RCTs found no significant effect on fasting glucose, insulin, HbA1c, or blood lipids.

The honest summary: NMN and NR are interesting compounds with a plausible mechanism and an acceptable safety profile at tested doses. They are not the rejuvenation pills they are often marketed as. If taking them, 300–600 mg NMN or 300–1,000 mg NR daily is within the studied range; their relative efficacy appears equivalent at matched doses (Nature Metabolism, 2026).

Myth 6: Longevity interventions are only relevant after 50

Biological ageing is not a cliff that appears in middle age — it is a continuous trajectory beginning in early adulthood. Epigenetic ageing clocks show detectable biological age drift in the 30s. Atherosclerosis, which causes most cardiovascular deaths, begins developing in the 20s in high-risk populations. VO2 max peaks in the late 20s to mid-30s and declines at approximately 1% per year without training — meaning fitness habits in the 30s and 40s largely determine the physiological baseline that enters the 60s and 70s.

The compounding nature of longevity interventions means that earlier adoption produces exponentially greater lifetime benefit. A 35-year-old who begins consistent Zone 2 training will enter their 60s with a VO2 max trajectory 15–20 ml/kg/min higher than a sedentary counterpart — the difference between independence and functional decline at 80.

References

1. Ruby, J. G., et al. (2018). Estimates of the heritability of human longevity are substantially inflated due to assortative mating. Genetics, 210(3).
2. Nature Medicine (2019). Replication of low longevity heritability estimates in independent genealogical dataset.
3. Kraus, W. E., et al. (2022). CALERIE trial: caloric restriction and biological ageing markers. Aging Cell.
4. NEJM (2022). Frailty as mortality predictor vs. obesity in older adults.
5. Windred, D. P., et al. (2024). Sleep regularity and mortality. SLEEP, 47(1).
6. Huang, Z., et al. (2024). NMN supplementation and metabolic markers: meta-analysis of 12 RCTs. Critical Reviews in Food Science and Nutrition.
7. Cuenoud, B., et al. (2026). NMN vs NR head-to-head comparison. Nature Metabolism.
8. Fleg, J. L., et al. (2005). Accelerated longitudinal decline of aerobic capacity in healthy older adults. Circulation, 112(5).