A review of over 350 studies has found that eating less protein may slow aging, improve metabolism, and sometimes extend lifespan.
This somewhat goes against the current trend of adding protein to many foods.
Dudley Lamming from the University of Wisconsin-Madison and a colleague looked at hundreds of studies and found several repeating biological patterns.
Their analysis suggests that eating less protein can change how cells sense nutrients, reduce cell damage, and help the body control energy and blood sugar.
Lamming agrees that protein is helpful for active people. “It’s absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals,” he said.
But for most people, who are not very active, he said they are “likely consuming more protein than they actually need, which probably has negative health consequences.”
The review does not prove that eating less protein makes people live longer . However, recent clinical trials found that people who ate less protein lost weight, reduced body fat, and improved fasting blood sugar, even when they ate more total calories.
Older adults in the US are eating more protein
These findings come at a time when people in the United States are eating more protein than ever.
This year, US authorities updated their guidelines to recommend 1.2 to 1.6 grams of protein per kilogram of body weight, or 0.5 to 0.7 grams per pound, which is almost double the previous amount.
Older adults especially are being told to eat more to keep their muscles strong.
Lamming’s team does not completely disagree with this advice. Losing muscle with age can increase the risk of weakness and falls, and eating more protein along with exercise can help prevent this.
The key, they say, is to personalize protein recommendations based on both age and physical activity.
“We probably need to personalize protein recommendations based not just on age, but also on how physically active people are,” Lamming said. The review also notes that pregnant women need more protein .
Study points out three amino acids behind the effect
The review pointed to one mechanism called fibroblast growth factor 21, or FGF21, a hormone that increases when people eat less protein.
Higher FGF21 can boost energy use, keep blood sugar steady, and reduce inflammation. In mice, those with more FGF21 lived longer, especially males. It is still not clear if this also happens in humans.
Total protein might not be the only factor. The review points to three amino acids—methionine, isoleucine, and valine—that, in excess, can activate growth pathways linked to obesity, inflammation, and age-related disease.
This suggests the connection between protein and aging is more complex than just eating more or less.
Not everyone thinks the evidence is strong enough yet. IBTimes Australia, as reported by Ground News, said that scientists want more and longer human trials before changing dietary advice.
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