Protein appears in cereal, coffee, and even bottled water. A major scientific review indicates that for many people, consuming less of it might slow aging and extend life.
Lower protein intake linked to longer lifespan
A new analysis of over 350 studies, published July 31 in Cell Press Blue, found that reducing protein intake may improve metabolism, limit cellular damage, and support normal cell function. The findings suggest protein restriction could provide health benefits comparable to calorie restriction, which has been shown to extend lifespan in animals and reduce age-related diseases.
Dudley Lamming, the study’s corresponding author and a researcher at the University of Wisconsin-Madison, stated that protein clearly benefits muscle growth and exercise performance in active individuals. However, since most people are relatively sedentary, many may consume more protein than necessary, which could have negative health effects.
Previous research demonstrated that flies and rodents lived longer on lower-protein diets, even without reducing calories. Human trials also revealed that participants who cut protein lost weight and body fat while improving fasting blood sugar, even when consuming more total calories.
Not all protein is equal
The analysis points to a hormone called fibroblast growth factor 21 (FGF21), which rises when protein intake decreases. Raised FGF21 levels have been associated with better blood sugar control, reduced inflammation, and longer lifespans in mice. The effect was stronger in males than females, and similar trends appear in human studies.
Specific amino acids—methionine, isoleucine, and valine—also influence these outcomes. Overconsumption of these compounds may overstimulate growth pathways, contributing to obesity, inflammation, and aging.
Lamming and his colleagues argue that sedentary adults may be consuming protein at levels that do more harm than good. “The amount of protein sedentary people are eating today may have negative health consequences, at least at the population level,” he explained.
Protein isn’t inherently harmful. The U.S. dietary guidelines were updated this year to recommend 1.2 to 1.6 grams of protein per kilogram of body weight—nearly double the previous amount. The change reflects evidence that higher protein intake helps older adults maintain muscle, particularly when paired with exercise.
Yet those benefits may not apply universally. Athletes often consume large amounts of protein without metabolic issues. Physical activity likely helps direct protein toward muscle maintenance rather than harmful metabolic processes.
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Personalized protein recommendations may be needed
The review indicates that protein requirements differ based on age and activity level. Pregnant women and some older adults may need more, while sedentary adults might benefit from less. A uniform approach may not address individual needs effectively.
“Recent guidelines have encouraged higher protein intake but also promoted more exercise,” Lamming noted. “We should tailor protein recommendations not just by age, but also by how active people are.”
For now, the evidence suggests a simpler principle: what suits a marathon runner may not be ideal for someone who sits at a desk most of the day. Translating this understanding into practical, individualized advice remains the next step.
The work received funding from the National Institute on Aging, the Wisconsin Partnership Program, and the University of Wisconsin-Madison.
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