Consuming less protein could have greater health benefits and may extend lifespan, according to a review published July 31 in the Cell Press journal Cell Press Blue. The review analyzed over 350 papers on protein restriction and aging, examining how reduced protein intake affects metabolism, cellular function, and longevity.
The authors report that restricting dietary protein slows aging by improving metabolism, altering cellular responses to nutrients, reducing cellular damage, and preserving healthy cell function. Dudley Lamming of the University of Wisconsin-Madison said, "It's absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals. But because most people are relatively sedentary, many people are likely consuming more protein than they actually need, which probably has negative health consequences."
While calorie restriction has long been known to extend lifespan in various organisms and reduce age-related diseases such as cancer, maintaining such a diet is challenging for most people. Previous studies have shown that eating less protein can increase the lifespan of flies and rodents without reducing calorie consumption. Recent clinical trials in humans indicate that reducing protein intake can lead to weight loss, decreased fat mass, and improved fasting blood sugar levels even when overall calorie consumption increases.
However, some research also finds that higher protein intake can promote weight loss and help prevent age-related muscle loss in older adults when combined with exercise. These findings led U.S. authorities this year to update dietary guidelines recommending an increase in daily protein intake for older adults from previous levels.
The review highlights mechanisms behind these effects—including increased levels of fibroblast growth factor 21 (FGF21) when dietary protein is low—which is linked to better energy expenditure, blood sugar control, reduced inflammation, and longer lifespans in animal models. Certain amino acids found in high-protein diets—such as methionine, isoleucine, and valine—may contribute to obesity or inflammation if consumed excessively.
Lamming said that while some groups like pregnant women or certain older adults require more dietary protein for health reasons, "the amount of protein sedentary people are eating today may have negative health consequences." He added, "Recent recommendations have encouraged people to eat more protein but they've also encouraged people to exercise more... We probably need to personalize protein recommendations based not just on age but also on how physically active people are."
