In a groundbreaking review published in the Cell Press journal Cell Press Blue, researchers have discovered that eating less protein could potentially slow down the aging process. The study, which examined over 350 studies on protein restriction and aging, suggests that many people may gain more benefits from reducing their protein intake, which could lead to a longer life.

The corresponding author of the paper, Dudley Lamming, a researcher from the University of Wisconsin-Madison, emphasizes that while protein is essential for muscle growth and exercise response in active individuals, most people consume more protein than they need, which may have negative health consequences.

For years, scientists have known that reducing calorie intake can lead to a longer lifespan in many organisms and lower the risk of age-related illnesses such as cancer. However, following a calorie-restricted diet over the long term is extremely challenging for most people. The review suggests that protein restriction may offer another route to achieve a longer lifespan.

Previous studies have found that flies and rodents lived longer when they consumed less protein, even when their overall calorie intake did not decline. Recent human clinical trials have also produced promising results, showing that people who lowered their protein intake lost weight and body fat and experienced improvements in fasting blood sugar levels, despite often consuming more total calories.

Why More Protein Can Still Be Beneficial

While the evidence suggests that eating less protein may slow down aging, other studies indicate that higher protein intake can support weight loss and help older adults preserve muscle, particularly when combined with exercise. These findings contributed to updated US dietary guidance this year, which recommends daily protein consumption of 1.2-1.6 grams per kilogram of body weight (0.5-0.7 grams per pound), nearly twice the previous amount.

Lamming and his colleague reviewed decades of evidence to better understand the relationship between protein, metabolism, and aging. Their analysis identified several recurring biological mechanisms that could explain why protein restriction may improve health and promote longevity. These mechanisms include better metabolic function, altered nutrient signaling, reduced cellular damage, and improved maintenance of healthy cells.

One important factor is fibroblast growth factor 21 (FGF21), a hormone that increases when protein intake falls. FGF21 can raise energy expenditure, improve blood sugar regulation, and reduce inflammation. Mouse studies have shown that animals with elevated levels of FGF21 lived longer than typical mice, and the effect was stronger in male mice than in female mice. Lower protein intake also increases FGF21 levels in humans.

The review also focuses on several amino acids, which are the individual building blocks of protein. Methionine, isoleucine, and valine appear to play especially important roles in protein restriction. Research suggests that excessive intake of these amino acids may activate biological pathways that encourage growth. When those pathways remain highly active, they may increase the risk of obesity, inflammation, and other conditions associated with aging.

Some groups clearly require more protein, such as pregnant women and certain older adults, who may have higher nutritional needs. For many sedentary adults, however, protein-fortified foods may not offer the health advantages they expect. Athletes often consume large quantities of protein without developing metabolic disease, which may be due to regular physical activity directing protein toward the development and maintenance of strong, healthy muscle.

Lamming suggests that protein recommendations may need to be personalized based not just on age but also on how physically active people are. This could lead to more effective protein guidance, which takes into account both age and activity level.

This work was supported by the National Institute on Aging, the Wisconsin Partnership Program, and the University of Wisconsin-Madison.