A comprehensive review of scientific literature suggests that consuming too much protein may have detrimental health consequences, potentially shortening lifespan, while reducing intake could confer significant benefits. The findings emerge amid a surge in popularity for high-protein diets, often promoted on social media for weight loss and muscle gain.
The review, which analyzed over 350 papers, indicates that a decrease in protein consumption could lead to reduced body weight, improved cardiovascular health, and an extended lifespan. Researchers from the University of Wisconsin-Madison propose that protein restriction might enhance metabolism, decrease inflammation, and limit cellular damage associated with aging.
While protein is essential for bodily functions such as repairing and building muscle, organs, and connective tissues, previous studies have indicated that limiting protein intake can extend the lifespan of model organisms like flies and rodents. Recent human trials have also shown that lower protein consumption can contribute to weight reduction and better blood sugar control, even when overall calorie intake remains similar.
One proposed mechanism involves a hormone called fibroblast growth factor 21 (FGF21). Lower protein intake appears to increase levels of FGF21, which may boost energy expenditure, improve blood sugar regulation, and reduce inflammation. Studies in mice have correlated higher FGF21 levels with longer lifespans, a benefit observed to be more pronounced in males.
However, experts caution that a significant portion of the evidence originates from animal studies, and findings may not directly translate to humans. The review also identifies specific amino acids that, when consumed in excess, could promote growth pathways linked to obesity, inflammation, and age-related diseases.
Dudley Lamming, the corresponding author of the review and a researcher at the University of Wisconsin-Madison, stated that while protein is vital for active individuals focused on muscle growth, many sedentary people likely consume more protein than necessary, leading to potential negative health effects. He noted that for most adults who are not highly active, protein-fortified foods may not deliver the expected health advantages.
Lamming suggests that personalized protein recommendations, taking into account an individual's activity level rather than just age, may be necessary. He speculates that athletes who consume large amounts of protein without apparent negative metabolic consequences may be protected by their regular exercise routines, which could utilize protein for muscle development.
Some experts remain skeptical, pointing out that the review heavily relies on research involving rodents and insects, which may not accurately reflect human aging processes. The National Health Service in the UK recommends that healthy adults consume 0.75 grams of protein per kilogram of body weight daily. For instance, a 60kg woman would aim for about 45g, and a 75kg man around 55g.
Concerns have also been raised about the potential strain of very high protein intakes on kidney function, particularly for individuals with pre-existing kidney conditions. In the UK, a significant portion of adults are overweight or obese, increasing their risk for various chronic diseases.