Protein is everywhere these days. From breakfast cereals to coffee to bottled water, manufacturers are adding extra protein to a growing range of everyday products. But as consumers are encouraged to eat more of it, a major scientific study suggests that reducing their protein intake could offer surprising benefits for health and longevity.
After reviewing more than 350 scientific articles, researchers found that reducing protein intake may help slow biological aging, improve metabolism and, under certain conditions, extend lifespan. The potential benefits appear to involve several processes that influence how the body uses energy, responds to nutrients, protects cells from damage, and maintains healthy cellular function.
The results, published in the journal Cell Press Blue Cell Pressraise an important question about the growing popularity of high-protein diets. Could many people be consuming far more protein than their bodies actually need?
“It is absolutely clear that protein has benefits for muscle growth and exercise response in active individuals,” says Dudley Lamming, the paper’s corresponding author, of the University of Wisconsin-Madison. “But because most people are relatively sedentary, many of them are likely consuming more protein than they actually need, which likely has negative health consequences.”
Why Eating Less Protein Could Promote Longevity
Scientists have long known that reducing calorie intake can extend the lifespan of many organisms. Research has also linked calorie restriction to a lower risk of diseases associated with aging, including cancer. However, regularly eating fewer calories is a challenge, making it difficult for many people to maintain such a diet over time.
An alternative approach is attracting growing scientific interest: reducing protein without necessarily eating less food.
Experiments involving flies and rodents have demonstrated that limiting protein intake can increase lifespan even when total calorie consumption remains unchanged. This suggests that the benefits of dietary restrictions may depend not only on the amount of food eaten, but also on the nutrients that make up that food.
Human research has also produced encouraging results. Several recent clinical trials have shown that people who reduce their protein intake can lose weight, decrease body fat, and improve their fasting blood sugar levels, even if they consume more calories overall. Fasting blood glucose measures blood glucose after a period of not eating and is an important indicator of metabolic health.
These results do not establish that protein restriction extends human lifespan, but they suggest that altering protein intake may influence processes associated with aging and disease.
The debate over how much protein we actually need
The situation becomes more complicated when exercise and muscle health come into play.
Other studies have shown that higher protein intake can promote weight loss and help older adults preserve muscle mass, especially when combined with physical activity. Muscle maintenance becomes increasingly important as we age, as muscle loss can contribute to weakness, reduced mobility and an increased risk of falls.
Research highlighting these benefits helped motivate U.S. officials to revise their dietary recommendations this year, encouraging a daily protein intake of 1.2 to 1.6 grams per kilogram of body weight (0.5 to 0.7 grams per pound). This is almost double the amount recommended previously.
As protein consumption reaches new heights in the United States and older adults are increasingly advised to eat more, Lamming and a colleague examined decades of research to better understand the relationship between protein intake and aging.
Their analysis brought together results from more than 350 articles, identifying several biological mechanisms that appeared repeatedly in the studies. Together, these mechanisms suggest that decreasing protein consumption could improve metabolic function, change how cells sense nutrients, limit cellular damage, and help preserve processes that keep cells functioning properly.
A hormone that could explain slower aging
One particularly intriguing finding concerns fibroblast growth factor 21 (FGF21), a hormone that becomes more abundant when dietary protein is limited.
FGF21 helps the body adapt to changes in nutrient availability and influences how energy is used. Higher levels of this hormone may increase energy expenditure, promote healthier blood sugar regulation, and reduce inflammation.
These effects are particularly interesting because metabolism and chronic inflammation are closely linked to aging. Over time, disruptions in these processes can contribute to conditions such as obesity, diabetes, and other age-related diseases.
Studies in mice have shown that animals with high levels of FGF21 live longer than mice with normal levels. The lifespan benefit was particularly strong in men, suggesting that biological sex may influence how the body responds to this hormone.
Researchers have also established that eating less protein increases FGF21 levels in humans. Whether this hormonal response produces the same longevity benefits seen in mice remains an important unanswered question.
How certain amino acids could influence aging
The amount of protein a person consumes may not be the only important factor. The types of amino acids that make up this protein could also play an important role.
Amino acids are the building blocks that the body uses to produce proteins, which are essential for maintaining muscles, repairing tissues, and carrying out countless cellular functions. Beyond these fundamental roles, certain amino acids also act as signals that influence metabolism and cell growth.
The review identifies three amino acids that seem particularly important: methionine, isoleucine and valine.
Research suggests that excess intake of these amino acids can stimulate biological pathways that promote growth. Although growth-related processes are essential for normal development and tissue repair, excessive or prolonged activation of certain pathways can contribute to obesity, inflammation, and other conditions associated with aging.
Limiting specific amino acids could therefore produce some of the benefits seen in low-protein diets. This possibility has attracted attention because it suggests that the relationship between protein and longevity may be more complicated than simply consuming a single nutrient.
“These studies show that the amount of protein that sedentary people consume today can have negative health consequences, at least at the population level,” says Lamming.
Why exercise might alter the effects of protein
Researchers point out that protein needs are not the same for everyone.
Pregnant women, for example, need additional protein to support fetal development, while some older adults need higher amounts to help maintain muscle and physical functions. People who exercise regularly may also benefit from eating more protein, as their muscles use these nutrients to recover, repair tissue, and adapt to training.
However, for many adults who spend most of their day sitting, adding protein to daily foods provides little additional benefit.
Lamming points out that athletes frequently consume large amounts of protein without developing the metabolic diseases sometimes associated with high-protein diets. One possible explanation is that physical activity changes the way the body handles these nutrients.
Regular exercise stimulates muscle growth and repair, potentially allowing the body to use additional protein for productive purposes while reducing some of the harmful metabolic effects associated with high protein intake.
This distinction may help explain why studies sometimes reach seemingly contradictory conclusions about proteins. A diet that benefits someone who exercises intensely may not be ideal for someone with a largely sedentary lifestyle.
Rather than recommending the same amount of protein for everyone, researchers argue that dietary advice should better reflect individual circumstances, including physical activity level and age.
“Recent recommendations have encouraged people to eat more protein, but they have also encouraged them to exercise more,” says Lamming. “We probably need to personalize protein recommendations based not only on age, but also on how active people are.”
The results challenge the assumption that adding more protein automatically leads to better health. Although protein remains essential, growing research on longevity suggests that, for some people, consuming less may offer benefits that have been overlooked in the rush to protein-rich foods.
The work was supported by the National Institute on Aging, the Wisconsin Partnership Program and the University of Wisconsin-Madison.
Gn Health
