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What the evidence supports after 40
This pillar holds to one rule: every claim is restated from the trial or guideline that measured it, with the guide linked and the source named. The four guides here cover strength, bone, brain and protein, and each one separates what the evidence supports from what it is often said to support.
Strength is the number to protect
The 2019 European consensus on sarcopenia (EWGSOP2) moved muscle strength ahead of muscle mass, because strength predicts adverse outcomes better. Its cutoffs for probable sarcopenia are a grip strength under 27 kg in men or 16 kg in women, or needing more than 15 seconds for five chair stands. The US Physical Activity Guidelines call for muscle-strengthening activity on 2 or more days a week alongside 150 to 300 minutes of moderate aerobic activity, and strength is trainable late in life: a 2009 Cochrane review of 121 trials in older adults found progressive resistance training improved muscle strength. Muscle after 40 explains the consensus and the guideline.
Bone: two different jobs
Exercise produces small, site-specific gains in bone mineral density and no source reviewed on this site reports a large one. The 2011 Cochrane review found progressive resistance training for the lower limbs best at the femoral neck and combination programs best at the spine. The stronger evidence in this field is about falls: Cochrane's 2019 review of 108 trials in adults 60 and over found exercise reduces the rate of falls by 23 percent on high-certainty evidence, driven by balance and functional exercise, and that review is uncertain about the effect of walking, or of resistance work without balance training, on falls. Bone loading and fall prevention are different jobs, which is the point of The best exercise to prevent osteoporosis.
Brain: one strong recommendation
WHO's second-edition guideline on reducing the risk of cognitive decline and dementia (July 2026) makes one strong recommendation on moderate-certainty evidence for adults with normal cognition: physical activity. It recommends against vitamin B, vitamin E, omega-3 and multivitamin or mineral supplements for this purpose in people without established deficiencies, strongly, and records insufficient evidence for interventions on depression, stroke, traumatic brain injury, vision or sleep specifically to lower dementia risk. The trials are mixed in an instructive way: SPRINT MIND was null on probable dementia and positive on mild cognitive impairment. How to reduce dementia risk reads the guideline and the trials together.
Protein: the requirement did not change
The RDA for protein is 0.8 g/kg a day and has not moved. Nitrogen-balance research re-analyzed in 2025 across 395 people found the same requirement and no difference by age, and the technique used to argue the RDA is too low finds the same shortfall in young adults. In a 6-month controlled-feeding trial in 92 functionally limited men aged 65 and over, 1.3 g/kg beat 0.8 on nothing: lean mass, strength, walking speed and stair power were all null. Protein after 40 sets the 2026 Dietary Guidelines' 1.2 to 1.6 g/kg figure against that evidence and explains where the two part ways.
Frequently asked questions
What is the one thing the evidence supports most strongly for aging well?
Physical activity. It is the only recommendation WHO's 2026 dementia guideline makes strongly on moderate-certainty evidence for adults with normal cognition, and balance and functional exercise drives the 23 percent reduction in the rate of falls that Cochrane rates high certainty. Strength training builds the strength the sarcopenia consensus measures.
Should I take a supplement for healthy aging?
The supplements pillar covers each one against its trials. For brain health specifically, WHO recommends against vitamin B, vitamin E, omega-3 and multivitamins for that purpose in people without established deficiencies.