Could eating less protein slow ageing?
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- Dudley Lamming at the University of Wisconsin-Madison led a review of more than 300 studies, mostly in sedentary rodents, examining how restricting protein to minimum required levels affects aging and lifespan
- Rats fed the US minimum protein intake (0.8 g/kg body weight) lived nearly 120 days longer — more than 50% — than those fed about double that amount in one study cited in the review
- Protein restriction raises FGF21 hormone levels and dampens mTORC1 activity, shifting cells from growth to repair and reducing senescent cells in rodents, per the review
- Donald Layman at the University of Illinois Urbana-Champaign argued rodents and humans differ fundamentally in protein metabolism — rodents graze throughout the day while humans eat fewer, larger meals, which alters mTORC1 activation patterns between species
- Layman noted the review excluded most human studies showing higher protein intake cuts frailty risk, limiting conclusions that can be drawn about people
- Elizabeth Williams at the University of Sheffield questioned a study linking higher protein intake to reduced sarcopenia risk, saying sarcopenia rates were too low to make the link reliable
- Philip Atherton at Nottingham University is planning a human trial of drugs that deplete specific amino acids — isoleucine and valine, highest in meat, fish, and dairy — to test whether blood sugar improvements seen in mice carry over, with results expected in the next few years
Why it matters: With protein-fortified products saturating shelves and US dietary guidelines now recommending 1.2-1.6 g/kg of protein for optimal health, this review challenges the "more is better" assumption — but only for sedentary individuals, since active people may need more for muscle repair. Atherton's upcoming human amino-acid drug trial will be the first real test of the rodent longevity findings.
