High-protein is a wellness craze, but could restricting it be anti-ageing?
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- Dudley Lamming at the University of Wisconsin-Madison and colleagues reviewed more than 300 studies, mostly in sedentary rodents, examining how restricting protein to minimum required levels affects aging and lifespan.
- In one study, rats fed the US guideline minimum of roughly 0.8 grams of protein per kilogram of body weight lived nearly 120 days — more than 50% longer — than rats fed about double that amount.
- Protein restriction appears to raise levels of the hormone FGF21, which acts on the brain, fat tissue and liver to improve blood sugar and reduce senescent cells that drive chronic inflammation, according to Lamming.
- Restricting protein also dampens activity of the cellular growth driver mTORC1, shifting cells from a proliferative, growth-focused state to one emphasizing repair.
- Donald Layman at the University of Illinois Urbana-Champaign countered that rodent metabolism differs fundamentally from humans, pointing to different mTORC1 activation patterns driven by rodents' grazing eating style versus humans' few large meals.
- Layman added the review excluded most human studies linking higher protein intake to reduced frailty risk, while Lamming said the team focused on restriction rather than high-protein studies.
- Philip Atherton at Nottingham University is planning a human trial of drugs that deplete specific amino acids such as isoleucine and valine — highest in meat, fish and dairy — with results expected in the next few years.
Why it matters: For sedentary consumers riding the high-protein wellness wave, the rodent evidence raises a question the industry has not had to answer: does eating above minimum requirements shorten lifespan? The translation to humans remains contested — Layman argues the review omitted most human evidence showing higher protein cuts frailty risk, keeping the debate unresolved for the multi-billion-dollar protein-supplement market.
