Eating less protein could slow aging, major review finds

A new review of over 350 studies on protein restriction and aging suggests that consuming less protein could potentially increase lifespan and improve overall health. Published in the Cell Press journal Cell Press Blue on July 31, the review explores the effects of reduced protein intake on metabolism, cell function, and cellular damage.

Corresponding author Dudley Lamming of the University of Wisconsin-Madison emphasizes that most individuals are likely consuming more protein than necessary, which may lead to negative health consequences due to sedentary lifestyles. While calorie-restriction has been known to promote longevity in various organisms, adhering to a long-term low-calorie diet is challenging for many people.

Protein restriction, however, may provide an alternative approach. Earlier research on flies and rodents revealed that reduced protein consumption resulted in longer lifespans, even when overall calorie intake remained constant. Similar findings have emerged from recent human clinical trials, where individuals who lowered their protein intake experienced weight loss, reduced body fat, and improvements in fasting blood sugar levels, despite consuming more total calories.

The review identifies several biological mechanisms that could explain the potential benefits of protein restriction. One such mechanism is the increase in fibroblast growth factor 21 (FGF21), a hormone that rises when protein intake decreases. FGF21 can enhance energy expenditure, improve blood sugar regulation, and decrease inflammation.

Mice studies have shown that those with higher FGF21 levels tend to live longer, with the effect being more pronounced in male mice than in female mice. In humans, lower protein intake also leads to increased FGF21 levels. Additionally, certain amino acids, such as methionine, isoleucine, and valine, may play crucial roles when consumed excessively.

These amino acids can activate biological pathways that promote growth, potentially increasing the risk of obesity, inflammation, and other aging-related conditions. The review highlights that the protein consumption of sedentary adults may have negative health consequences at a population level. While some groups, such as pregnant women and certain older adults, require higher protein intake, the review suggests that protein-fortified foods may not offer the expected health benefits for most sedentary adults.

Athletes, however, often consume large amounts of protein without developing metabolic diseases, possibly due to the protective effects of regular physical activity. The review emphasizes the need for personalized protein recommendations, taking into account both age and physical activity level, rather than applying a one-size-fits-all approach.

The findings suggest that protein guidance should be tailored to individual needs, considering both age and activity level, for optimal health outcomes. This research was supported by the National Institute on Aging, the Wisconsin Partnership Program, and the University of Wisconsin-Madison.