Eating less protein could slow aging, review of 350 studies finds

Dudley Lamming of the University of Wisconsin-Madison and colleagues examined more than 350 scientific papers and found evidence that reducing protein intake may slow biological aging, improve metabolism, and potentially extend lifespan. The findings appear in the Cell Press journal Cell Press Blue.

The review identified several biological mechanisms that repeatedly appeared across studies. Lowering protein consumption may improve metabolic function, alter how cells detect nutrients, limit cellular damage, and help preserve cellular function. One mechanism involves fibroblast growth factor 21 (FGF21), a hormone that becomes more abundant when dietary protein is limited. Studies in mice showed that animals with elevated FGF21 levels live longer than mice with normal levels, particularly in males.

Experiments in flies and rodents demonstrated that limiting protein intake can increase lifespan even when total calorie consumption remains unchanged. Human clinical trials showed that people who reduce protein intake can lose weight, decrease body fat, and improve fasting blood sugar levels, even when consuming more calories overall.

Lamming notes that the benefits may depend on activity level. "It's absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals," he says. "But because most people are relatively sedentary, many people are likely consuming more protein than they actually need, which probably has negative health consequences."

The review also examined three amino acids that appear especially important: methionine, isoleucine, and valine. Excessive intake of these amino acids can stimulate biological pathways that encourage growth, potentially contributing to obesity, inflammation, and other age-related conditions.

The researchers stress that protein requirements vary. Pregnant women and some older adults require higher amounts, and people who exercise regularly may benefit from greater protein consumption to support muscle recovery and adaptation to training. Athletes frequently consume large amounts of protein without developing the metabolic diseases sometimes associated with protein-rich diets, possibly because physical activity changes how the body handles those nutrients.