Walk down any grocery aisle these days and you will spot it: protein-fortified cereals, protein bars, protein-packed chips, even protein water. The message is clear that more protein equals better health. But a sweeping review of more than 350 scientific studies published Friday suggests that for many Americans, all this extra protein may actually be doing harm rather than good. The review, published in Cell Press Blue, found that reducing protein intake instead of increasing it could slow aging and potentially extend lifespan, challenging the assumptions driving a multi-billion-dollar food industry trend.
Dudley Lamming, the review’s corresponding author at the University of Wisconsin-Madison, said most people are likely consuming far more protein than they need because they lead relatively sedentary lives. The average American man eats nearly 100 grams of protein daily, roughly twice what was previously recommended before the Trump administration adjusted dietary guidelines under Health Secretary Robert F. Kennedy Jr. Those new guidelines recommend a daily intake of 1.2 to 1.6 grams per kilogram of body weight, nearly double the earlier target. Lamming argues that recommendations should account not just for age but also for physical activity levels.
The science behind the warning comes down to how different nutrients interact with the body’s aging pathways. When people cut back on protein, a hormone called fibroblast growth factor 21 rises, boosting energy, improving blood sugar control, and reducing inflammation. On the flip side, certain amino acids found in high-protein diets such as methionine, isoleucine, and valine appear to activate growth pathways linked to obesity, inflammation, and age-related diseases. Human clinical trials have shown that participants who ate less protein lost weight and body fat while improving their fasting blood sugar, even when consuming more total calories overall.
There is an important catch though. Athletes and highly active individuals seem protected from the downsides of high protein consumption because exercise channels those extra amino acids into muscle tissue instead of disease-related pathways. For everyone else spending their days behind desks or on couches, the surplus protein has nowhere productive to go. As grocery store shelves continue filling with ever more protein-enriched products aimed at consumers chasing longevity and vitality, researchers say the real secret to a longer life might simply mean eating less of exactly what everyone keeps telling us to eat more of.