Eating less protein may ‘slow’ ageing. But here’s why the evidence isn’t clear-cut

The Conversation walks through a new research review examining over three hundred fifty studies on protein and aging. The findings suggest eating less protein may slow biological aging—the mechanism involves how the body uses energy and removes cellular waste. But most of the convincing evidence comes from laboratory animals like mice and rats, not humans. In animal studies, lower-protein diets were linked to longer lifespans and signs of healthier aging. When researchers looked at human studies, however, the picture got murkier. Most human trials lasted only a few weeks, far too short to measure actual lifespan or aging effects. There's more nuance too: higher-protein diets can preserve muscle mass in older adults, help prevent frailty, and make people feel fuller longer. Restricting specific amino acids—particularly methionine, isoleucine, and valine—may produce the same benefits as restricting all protein. Even populations known for exceptional longevity muddy the waters: the Mediterranean diet supports healthy aging with moderate protein, while the traditional Okinawan diet has little protein but emphasizes plant foods and overall caloric moderation. The author's conclusion? Stick with current protein recommendations, eat minimally processed protein sources, and remember that longevity is shaped by much more than one nutrient: regular exercise, quality sleep, strong social connections, stress management, and not smoking all matter just as much, if not more.

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