Protein has become the darling of the grocery store, pumped into everything from cereal and coffee to bottled water. But a sweeping new review of more than 350 studies suggests that this obsession might be backfiring for many people. Researchers from the University of Wisconsin-Madison found that eating less protein could actually slow aging, improve metabolism, and extend lifespan, challenging the notion that more protein is always better.
The review, published July 31 in the journal Cell Press Blue, identified several biological mechanisms that explain why cutting back on protein might be beneficial. Lower intake was linked to reduced cellular damage, better blood sugar regulation, and improved maintenance of healthy cells. One key player appears to be a hormone called fibroblast growth factor 21, or FGF21, which naturally rises when protein consumption drops. Mouse studies showed that animals with elevated FGF21 levels lived longer, though the effect was stronger in males than females.
Dudley Lamming, the paper’s corresponding author, acknowledges that protein remains essential for athletes and highly active individuals looking to build muscle. The problem, he says, is that most Americans are relatively sedentary yet consuming more protein than they need. Certain amino acids found abundantly in protein, particularly methionine, isoleucine, and valine, may activate growth pathways that, when constantly switched on, increase the risk of obesity, inflammation, and other age-related conditions.
The findings complicate recent dietary guidance that nearly doubled recommended protein intake to 1.2 to 1.6 grams per kilogram of body weight daily. Lamming argues that recommendations should account for activity level rather than applying a one-size-fits-all approach. Pregnant women, older adults at risk of muscle loss, and people who exercise regularly likely benefit from higher intake, but sedentary adults pouring protein powder into their morning coffee may want to reconsider. As Lamming puts it, the amount of protein most people are eating today probably carries negative health consequences at the population level, even if those effects take years to become apparent.