Which health interventions have the greatest impact on living longer?
Exercise, a Mediterranean diet, adequate sleep, social contact and quitting smoking each have a measurable influence on how long you live in good health. Combining several healthy habits brings the greatest benefit.
Physical activity has the strongest support of all interventions studied. Every 1,000 extra steps per day is associated with a 15% lower risk of dying; every 500 extra steps with a 7% lower risk of death from heart and vascular disease. A combination of aerobic exercise and strength training also reduces the risk of physical frailty in later life by around 33%. Whether exercise is the direct cause, or whether healthier people simply move more, cannot be entirely ruled out, but the pattern is consistent across dozens of large studies.
Diet is the second major lever. The Mediterranean diet, combined with adequate protein and plenty of vegetables and fruit, is associated with 22% fewer heart and blood vessel problems and 28% less mental decline in people over 50. Eating an extra 200 grams of vegetables and fruit every day is linked to a 10% lower risk of early death, and that benefit continues up to around 800 grams per day. The risk of stroke falls by 16% with that same extra 200 grams.
Quitting smoking is the single most impactful behaviour change for people who smoke: a 32% lower risk of heart and blood vessel disease. For smokers, this delivers more health benefit than any other intervention.
Mental and social health deserve just as much attention as diet and exercise. Keeping the mind active and practising mindfulness are associated with a 25% lower risk of dementia. Social contact and community involvement reduce the risk of depression by 30%. Seven to eight hours of sleep per night is associated with 25% less cognitive decline; for people with sleep problems, a talking therapy focused on changing sleep habits works well.
The greatest gain in independent living at an advanced age comes from a combination: a healthy lifestyle together with a strong social environment. Men gain almost four extra years of independent life compared with people who have few favourable factors; for women the gain is similar. Women appear to benefit relatively more from social circumstances such as income and social support, men more from lifestyle improvements. Regular health check-ups and vaccinations prevent complications and hospital admissions. They detect chronic conditions 40% more often at an early stage and reduce flu-related hospital admissions by 42%.
This answer draws mainly on several large summaries combining dozens of studies, including an analysis of 35 studies involving around 25,000 participants (covering diet, exercise, cognition and smoking), an analysis of 95 studies that followed people over time (for vegetables and fruit), and an analysis of more than 200,000 people followed over time (for step counts). The findings on exercise and diet are therefore the most solidly supported. The combined effects of lifestyle and social circumstances come from a long-running study of more than 11,000 people; that shows an association, but not proof of cause and effect. The researchers behind the review on exercise and healthy ageing themselves point to large differences between the individual studies, which means the exact size of the effect is uncertain.
What are the benefits of fermented foods?
Fermented foods show real benefits for antioxidant activity and digestibility, and there are indications that they may support resistance to infection. For claims around mental health and ADHD, the research is still too limited to draw any meaningful conclusions.