Could Reducing Your Protein Intake Promote Healthy Aging?
A new review suggests that protein restriction may improve metabolic health and lifespan. However, the review is not without critics.
If you're a regular at the gym or the running track, you likely supplement your diet with protein powders or protein-fortified foods. Even more sedentary people often choose the high-protein option when comparing two foods, as high-protein meals are generally more "filling," or satiating.
Consuming enough of this valuable macronutrient makes sure that your body has the necessary building blocks, or amino acids, to repair and build new muscle tissue and replenish muscle glycogen stores—a vital part of post-exercise recovery.
But according to a new review, published in Cell Press Blue, protein restriction may be better for you as you age. The review, which drew on more than 350 papers looking at the effects of protein restriction and aging, found that the restriction of some amino acids may promote metabolic health, healthspan, and lifespan across a variety of animal models.
“It's absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals,” said Dr. Dudley Lamming, the paper’s corresponding author and a professor at the University of Wisconsin-Madison, in a press release. “But because most people are relatively sedentary, many people are likely consuming more protein than they actually need, which probably has negative health consequences."
Dietary restriction and aging
The idea of dietary restrictions affecting aging is not new; data from observational, preclinical, and clinical trials suggest that eating a nutritionally balanced calorie-restricted diet can improve quality of life and extend lifespan in elderly people.
In the new Cell Press Blue paper, the authors highlight more than 350 papers from decades of research covering a very similar intervention—restricting dietary protein intake.
Using these studies, which examined the effects of protein restriction on the lifespan and health of different animal models, the authors outlined potential mechanisms that could explain these effects by highlighting numerous "hallmarks" of protein restriction in animals, including changes in metabolic function, nutrient-sensing, mitochondrial function, and epigenetic modifications.
For example, the paper claims that a primary mediator of the metabolic benefits of protein restriction is a hormone called fibroblast growth factor 21 (FGF21). The mouse studies analyzed by the authors consistently showed that those with higher levels of FGF21—which rises when protein intake is low—tended to live longer than regular mice. Low-protein diets are also known to increase circulating FGF21 levels in humans.
The authors also suggested that the restriction of several individual amino acids—including methionine, leucine, isoleucine, and valine— are "likely the primary drivers" of the benefits of protein restriction on lifespan in both fruit fly and mouse models. Some of the studies included in the paper suggest that consuming too much of these amino acids could increase the risk of obesity, inflammation, and other age-related diseases.
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However, it is important to note that the Cell Press Blue paper, while published as a "review," does not follow the structure of a typical systematic review.
"In a systematic review, the researchers make efforts to find all the papers and research reports that are relevant to the question of interest. There are accepted standards for how to carry out a systematic review, and how to report it," explained Prof. Kevin McConway, emeritus professor of applied statistics at the Open University, in comments given to the Science Media Centre. “This paper doesn’t claim to be a systematic review. Instead it is a narrative review of the literature."
"The authors have clearly based their findings on a large number of research papers, and it’s beyond my expertise to comment on whether they missed any important ones. But they don’t explain how they chose the papers to review, and they don’t use statistical methods to combine the findings." — Prof. Kevin McConway.
"I’m absolutely not criticising the authors of the paper for using this approach. It’s a common way of reviewing a field of study. But I wanted to mention that it’s not a systematic review, in case anyone thinks that it will have the characteristics that a systematic review should have," he said.
Does this mean we should be eating less protein?
Speaking about the paper, Lamming said: “These studies show that the amount of protein sedentary people are eating today may have negative health consequences, at least at the population level."
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"Recent recommendations have encouraged people to eat more protein, but they've also encouraged people to exercise more," Lamming continued. "We probably need to personalize protein recommendations based not just on age, but also on how physically active people are."
While this recommendation may be appropriate for some contexts, other scientists caution that more human data is needed before appropriate conclusions can be drawn.
"It is a comprehensive, interesting, and timely review, but it is not a new clinical trial, nor does it prove that reducing protein intake prolongs human life. The most compelling evidence on longevity still comes from animal models, whilst studies in humans are few and, generally speaking, of short duration," Prof. José M. Ordovás, senior scientist and scientific advisor at the Jean Mayer USDA Human Nutrition Research Center on Aging and a professor of nutrition and genetics at Tufts University, told the Science Media Centre Spain.
"The study serves as a counterbalance to the increasingly widespread notion that more protein is always better. However, it does not justify recommending less protein for everyone: requirements vary according to age, physical activity, nutritional status, and clinical condition." — Prof. José M. Ordovás.
"We should not replace the slogan ‘more protein is better’ with another equally simplistic one: ‘less protein prolongs life’. The sensible message is to consume an adequate amount—not necessarily the maximum—paying attention to the quality and source of food and tailoring intake to each individual," Ordovás concluded.
Reference: Knopf BA, Lamming DW. The hallmarks of protein and amino acid restriction in aging and longevity. Cell Press Blue. 2026. doi: 10.1016/j.cpblue.2026.100079
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