Reduce protein to increase longevity? Nutrition experts say that’s a bad idea

Reduce protein to increase longevity? Nutrition experts say that’s a bad idea A recent review paper published in Cell Press has sparked debate among nutritionists and scientists, suggesting that reducing dietary protein might promote metabolic health, extend healthspan, and even increase lifespan. However, leading experts warn that such conclusions lack sufficient human evidence and could pose serious risks to older adults and others with specific health conditions. The study, authored by researchers from the University of Wisconsin-Madison’s Department of Medicine, analyzed 350 previously published research papers. It argued that protein restriction, defined as lowering total dietary protein intake while still meeting nutritional needs, could serve as a robust geroprotective regimen. The authors emphasized the potential therapeutic value of such diets for promoting healthy aging and longevity. Critics, however, argue that the study’s recommendations are based largely on animal research and cannot be reliably applied to humans. Stuart Phillips, a professor of kinesiology and skeletal muscle health expert at McMaster University, called the study “a beautiful mouse story, sold as human advice.” He pointed out that in people over 65, particularly in the very elderly, lower protein intake is associated with worse outcomes, including greater frailty, more frequent falls, and higher mortality rates. Phillips added that the study acknowledges the uncertainty surrounding the effects of protein restriction on human lifespan, a key limitation. “That is the central limitation,” he said. “The authors admit that the impact of protein restriction on human lifespan is unknown.” The latest Dietary Guidelines for Americans, issued in early 2026 by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture, recommend 1.2 to 1.6 grams of protein per kilogram of body weight. Most Americans meet this range, according to Donald Layman, a professor emeritus of nutritional sciences at the University of Illinois Urbana-Champaign, who contributed to setting the guidelines. The Recommended Dietary Allowance (RDA) for protein, established by the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine, sets the minimum daily intake at 0.8 grams per kilogram of body weight. While the RDA is set at two standard deviations above the physiological need, the actual minimum requirement is much lower. Nonetheless, Phillips notes that older adults may require more protein than the RDA suggests due to age-related changes in metabolism and muscle synthesis. Stacy Pelekhaty, a registered dietitian and senior clinical nutrition specialist at the University of Maryland Medical Center, observes that many of her patients begin focusing on longevity in midlife. Often, they already face challenges such as chronic injuries or illnesses, which may elevate their protein needs. Pelekhaty emphasizes that addressing these issues often requires adequate protein intake rather than reduction. William Evans, a protein and aging researcher at the University of California, Berkeley, agrees that the notion of extending lifespan through protein restriction is questionable. He explains that as humans age, the body’s capacity to synthesize protein declines along with overall metabolism, increasing the demand for dietary protein to preserve lean muscle mass. Evans expressed skepticism toward the proposed benefits of a protein-restricted diet, noting that maximal lifespan does not equate to a healthier, more functional later life. He further cautioned against conflating extended lifespan with improved quality of life for older adults. “Longevity doesn’t necessarily mean better care for geriatric patients,” Evans said, stressing the importance of considering both quantity and quality of life when evaluating dietary strategies.