As high-protein foods continue to gain popularity—with protein now added to products ranging from breakfast cereals to coffee and even bottled water—a new scientific review suggests that, for many people, reducing protein intake may provide greater health benefits than increasing it.
The review, published in Cell Press Blue, analyzed findings from more than 350 scientific studies examining the relationship between protein restriction, aging, and lifespan.
The authors concluded that moderate reductions in protein intake may help slow the aging process by improving metabolism, altering cellular nutrient-sensing pathways, reducing cellular damage, and supporting normal cell function.
Animal studies have shown that protein restriction can extend lifespan in species such as flies and rodents. Some human studies have also reported benefits, including weight loss, reduced body fat, and improved fasting blood glucose levels among people consuming lower-protein diets.
However, the researchers emphasize that the issue is complex. Other studies have found that higher protein intake, when combined with regular exercise, can help preserve muscle mass in older adults and support weight loss. As a result, some countries have recently revised their dietary guidelines to recommend higher protein intake.
One of the key biological mechanisms under investigation involves the hormone FGF21. Protein restriction increases FGF21 levels, which may enhance energy expenditure, improve blood sugar regulation, and reduce inflammation. In animal studies, mice with higher FGF21 levels lived longer.
The researchers also highlighted the role of specific amino acids—the building blocks of protein—including methionine, isoleucine, and valine. Excessive intake of these amino acids may activate growth-related pathways that have been linked to obesity, chronic inflammation, and age-related diseases.
The authors stress that protein requirements vary depending on lifestyle and individual needs. Pregnant women, athletes, and some older adults may require higher protein intake. In physically active individuals, regular exercise likely helps direct dietary protein toward maintaining and building muscle.
According to the researchers, the findings do not suggest eliminating protein from the diet but rather identifying the optimal intake. For many sedentary individuals, the current trend toward consuming increasingly high amounts of protein may not be necessary or beneficial.
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