Reducing dietary protein intake can slow biological aging and improve metabolic health, according to a major scientific review published in the Cell Press journal Cell.
Researchers examined more than 350 scientific papers to evaluate how lower protein consumption affects lifespan and cellular function in humans and animals.
While high-protein diets remain popular for muscle growth, the new findings suggest that many sedentary individuals consume more protein than necessary. “It’s absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals,” said Dudley Lamming, the paper’s corresponding author of the University of Wisconsin-Madison.
“But because most people are relatively sedentary, many people are likely consuming more protein than they actually need, which probably has negative health consequences.”
Limiting Protein Increases FGF21 Hormone Levels
The review identified several biological mechanisms that link protein restriction to slower aging, including changes in how cells detect nutrients. Limiting protein increases levels of fibroblast growth factor 21 (FGF21), a hormone that helps regulate energy expenditure, blood sugar, and inflammation. Studies in mice show that elevated FGF21 levels extend lifespan, particularly in males.
Beyond total protein amounts, specific amino acids drive these metabolic responses. Excessive intake of methionine, isoleucine, and valine can stimulate biological pathways that encourage cell growth. Prolonged activation of these pathways contributes to inflammation and age-related metabolic conditions.
Protein Requirements Vary by Activity Level
Protein requirements vary depending on age, pregnancy status, and physical activity. Athletes and individuals who exercise regularly use extra protein for muscle repair, which offsets some negative metabolic effects seen in sedentary populations. U.S. guidelines recommend daily protein consumption of 1.2 to 1.6 grams per kilogram of body weight to support muscle preservation in older adults.
| Group | Recommended Intake | Primary Benefit |
|---|---|---|
| Sedentary Adults | Lower intake levels | Improved metabolic health and slower biological aging |
| Active Individuals | 1.2–1.6 g per kg of body weight | Muscle growth, recovery, and tissue repair |
| Older Adults | 1.2–1.6 g per kg of body weight | Preservation of muscle mass and prevention of falls |
Lamming emphasized tailoring dietary guidance rather than applying uniform standards across the population. “Recent recommendations have encouraged people to eat more protein, but they’ve also encouraged people to exercise more,” Lamming said. “We probably need to personalize protein recommendations based not just on age, but also on how physically active people are.”
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