Study review suggests lower protein intake may slow aging, boost metabolism

A scientific review of more than 350 studies, published in a journal from Cell Press and reported by Science Daily, has found that reducing protein intake may slow biological aging, improve metabolic processes, and potentially extend lifespan.

Lead researcher Dudley Lamming from the University of Wisconsin-Madison explained that while protein is essential for building muscle and supporting exercise response, many people—especially those with low physical activity—consume more than they need, which could have unwanted health effects.

The review noted that calorie restriction has been shown to extend lifespan and lower the risk of age-related diseases in many organisms, but maintaining such a diet long-term is challenging.

As a result, scientists have focused on the quality of food as well as quantity. Experiments in flies and rodents showed that reducing protein intake could increase average lifespan even when total calorie intake remained the same.

Human studies also indicated that lowering protein may help with weight loss, reduce body fat, and improve fasting blood sugar levels, although these findings do not directly prove increased lifespan in humans.

Conversely, other research highlights the importance of protein for maintaining muscle mass, particularly in older adults and those who are physically active, as muscle preservation is key to preventing frailty, mobility decline, and increased fall risk with age.

One possible explanation for these findings is that reducing protein intake raises levels of the hormone FGF21, which helps the body adapt to dietary changes, regulate energy use and blood sugar, and reduce inflammation—factors linked to aging.

Researchers also pointed to the role of certain amino acids in protein, such as methionine, isoleucine, and valine. Evidence suggests that excessive intake of these amino acids may activate biological pathways related to growth, but prolonged activation could contribute to obesity, inflammation, and age-related diseases.

The researchers believe that restricting specific amino acids may offer some of the benefits of low-protein diets, indicating that the relationship between protein and longevity is more complex than simply increasing or decreasing total intake.

The review concludes that while protein remains an essential nutrient, growing evidence suggests that reducing intake could provide health benefits for some people, challenging the common belief that more protein always leads to better health.