Protein is on everyone’s mind, and for older adults, it should be.
Nutrition experts say that’s worth a reminder after researchers recently suggested there’s evidence that “dietary protein restriction promotes metabolic health, healthspan, and lifespan.”
In a review paper published in Cell Press Blue, the authors described several biological mechanisms through which a protein-restricted diet can improve longevity. According to experts, their arguments are less than convincing. Nutrition professionals warned that following their advice could put older adults, people with a sedentary lifestyle, and those on GLP-1 weight loss medications at serious health risk.
Stuart Phillips, a professor of kinesiology and skeletal muscle health expert at McMaster University, described the study as “a beautiful mouse story, sold as human advice” in a social media post. “In people over 65, and especially in the very old, low protein is linked to worse outcomes, not better ones,” he said, adding, “More frailty. More falls. Higher mortality.”
In the study that Phillips was critiquing, the authors — from the University of Wisconsin-Madison’s department of medicine — drew on the findings from 350 previously published research papers to offer “a comprehensive overview of current knowledge regarding the benefits of [protein restriction] and amino acid restriction for healthy aging, and highlights the therapeutic potential of interventions based on these diets to promote healthspan and longevity.”
Notably, a lot of the previous evidence the authors drew on were from animal research. That evidence, Phillips told STAT, cannot be directly translated to improved longevity in humans. “The authors acknowledge that the effect of protein restriction on human lifespan is unknown. That is the central limitation,” he said.
As the authors describe it in the review, “protein restriction, is a robust geroprotective regimen that lowers total dietary protein intake while still meeting nutritional needs.” That, experts say, is challenging to interpret within the context of humans and the wide range of nutritional needs seen across the lifespan.
The latest Dietary Guidelines for Americans, jointly released by the federal health and agriculture departments in early 2026, recommend 1.2 to 1.6 grams of protein per kilogram of body weight. The majority of Americans are meeting this higher range according to Donald Layman, a professor emeritus of nutritional sciences at the University of Illinois Urbana-Champaign who helped to set the dietary guidelines.
Similarly, the Recommended Dietary Allowance — set by the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine — recommends 0.8 grams of protein per kilogram of body weight. The RDA is set at two standard deviations above the physiological need, so the true minimum protein requirement is well below that. Still, Phillips noted that older adults may need more protein than the RDA recommends.
Stacy Pelekhaty, a registered dietitian and senior clinical nutrition specialist at the University of Maryland Medical Center, finds that most of the patients she works with start focusing on longevity in the middle of life. By that time, Pelekhaty said patients are “starting to live with more chronic injuries or illness,” and it’s likely many individuals would have higher protein needs.
As humans age, the body’s ability to synthesize protein slows down alongside metabolism, creating an increased demand for dietary protein to maintain lean muscle, said William Evans, a protein and aging researcher and adjunct professor of human nutrition at the University of California, Berkeley. For older adults, Evans said he is “very skeptical” of the proposed benefits of a protein restricted diet.
Evans also cautioned against confusing maximal lifespan for a healthy lifespan. “Longevity doesn’t necessarily mean better care for geriatric patients,” he said, adding that it’s important to consider questions like “‘How do we keep older adults out of nursing homes?’ and ‘How do we help them live a functional, independent life?’”
Katie Dodd, who hosts the podcast “Geriatric Dietitian,” focuses her clinical practice on extending the health and wellness of older adults. Dodd cited the PROT-AGE study — initiated by the European Geriatric Medicine Society to develop evidence-based recommendations for dietary protein intake in older people — which recommends 1-1.2 grams of protein per kilogram of body weight for older adults, with higher intake for those who exercise regularly.
“Healthy aging isn’t just about living longer. It’s about maintaining the strength and function to enjoy those extra years,” Dodd said, adding that reducing protein intake could accelerate muscle loss and threaten an individual’s independence.
In a press release, the authors of the Cell Press Blue paper noted that sedentary individuals in the U.S. probably overeat protein and may benefit from a protein-restricted diet — a claim that several experts were concerned about given the authors did not quantify the amount of protein recommended for that population.
Sedentary individuals still require enough protein to maintain their lean tissue according to Evans, who believes the RDA of 0.8 grams per kilogram of body weight is adequate. Exercise helps individuals maintain lean tissue, Evans said, so in sedentary individuals, reducing protein intake could speed up muscle loss over time.
Pelekhaty, the clinical nutrition specialist, noted that if sedentary individuals reduce their protein intake without reducing overall calories, it will be replaced by other macronutrients. Higher carbohydrate intake, for instance, could increase the risk of chronic metabolic conditions that will impact longevity and quality of life.
When those with a sedentary lifestyle are on GLP-1 medications for weight loss, the risks are higher according to Pelekhaty. GLP-1 medications are associated with loss of muscle mass and decreased metabolic rate, making adequate protein intake and physical activity especially critical to maintaining lean tissue. GLP-1 medications paired with the satiety of protein-rich meals can make individuals feel full for longer, she said, making it harder to consume enough protein.
Beyond raising questions about how many grams of protein people should be eating, experts said the types of protein are also important to consider. Some said plant-based proteins could reduce the risk of diabetes and heart disease thanks to the lower saturated fat, compared to animal products.
On that point, Phillips noted that authors of the new review paper, and others researching premature mortality, seem to coalesce on the “more beans and less bacon” approach, rather than a blanket protein restriction. “A mixture of minimally processed plant and animal foods is very different from simply adding protein bars, powders, and ‘protein-fortified’ snack foods to an otherwise poor diet,” he said.
Dodd clarified that protein goals should be individualized based on a person’s age, health status, muscle mass, kidney function, activity level, and overall goals. And experts agreed that functional health should be prioritized over longevity.
Illinois’ Layman said, “I think it’s far better to be an active 90-year-old than being a vegetable at 100.”