Eating less protein for longevity: experts push back

An idea circulating in longevity circles holds that eating less protein favorably affects metabolism and extends lifespan. That idea is based on animal research and mechanistic insights, but its translation to human practice is contested. The nutrition experts quoted by STAT question the recommendation, particularly for people over fifty.

The logic behind protein restriction

In laboratory studies in animals, and in some human studies, protein has been associated with activation of mTOR (mechanistic target of rapamycin), a protein that regulates cell growth and metabolism. When mTOR is less active, cells shift toward repair processes rather than growth. That mechanism is linked to slowed aging in multiple model organisms. Restriction of the amino acid methionine, a component of proteins, extended lifespan in mouse models.

Based on such findings, some researchers suggested that protein restriction might also benefit healthspan and lifespan in humans.

The caveats

Nutrition experts point to a crucial distinction: what works in mice or worms does not necessarily apply to humans. Moreover, protein needs change with age. After the age of fifty, the body’s efficiency in converting protein into muscle mass declines. Eating less protein then risks accelerated muscle loss (sarcopenia). That in turn increases the risk of falls, functional limitations, and a shorter lifespan.

Current recommendations for older adults are generally higher than for younger adults, not lower. Experts emphasize that protein quality, distribution across the day, and combination with physical exercise are at least as important as quantity.

This article reflects an ongoing scientific debate, not an established consensus. The experts quoted offer their professional judgment; individual recommendations remain a matter for one’s healthcare provider.

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