Like so many food issues, fads are often fake and balance is the key
The
authors describe how protein restriction slows aging by improving metabolism,
changing how cells respond to nutrients, reducing cellular damage, and
preserving healthy cell function.
"It's absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals," says 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."
For decades, scientists have known
that eating less calories can extend lifespan in many organisms
and reduce the risk of age-related diseases like
cancer. But maintaining a calorie-restricted diet is difficult
for most people.
Previous studies have found that eating
less protein can extend the lifespan of flies and rodents
without reducing their calorie consumption. Several recent clinical
trials in humans have also shown that reducing protein intake can
reduce weight and fat mass and improve fasting blood sugar in humans,
even though protein-restricted individuals tend to eat more calories.
But at the same time, some studies have found
that eating more protein could promote weight loss and
reduce age-related muscle loss in older adults when
paired with exercise. Those findings prompted US authorities to
update its dietary guidelines this year, recommending an increase
in daily protein intake to 1.2–1.6 grams per kilogram of body weight
(0.5–0.7 grams per pound), nearly doubling the previous recommendations.
With Americans consuming more protein than ever and older adults encouraged to boost their intake, Lamming and his colleague set off to review decades of research on protein restriction and aging. Drawing on more than 350 papers, the team outlined potential mechanisms that consistently emerge across studies and may explain how protein-restricted diets could improve health and promote longevity. These mechanisms suggest that protein restriction slows aging by improving metabolism, changing how cells respond to nutrients, reducing cellular damage, and preserving healthy cell function.
One of the key players is a
hormone called fibroblast growth factor 21 (FGF21), which rises
when protein intake is low. FGF21 can increase the body's energy
expenditure, improve blood sugar control, and reduce inflammation. Studies
in mice have shown that animals with higher FGF21 levels lived longer
than normal mice, and the benefit was more pronounced in male mice than
female mice. Eating less protein raises FGF21 levels in humans as
well.
The review also highlights several amino
acids, the building blocks of protein, that appear to drive many of
these effects, including methionine, isoleucine, and
valine. Studies show that consuming too much of these amino
acids could trigger biological processes that promote growth,
increasing the risk of obesity, inflammation, and other
age-related diseases.
"These studies show that the amount of
protein sedentary people are eating today may have
negative health consequences, at least at the population
level," Lamming says.
He adds that while some people, like pregnant
women and some older adults, have higher protein needs, for most
sedentary adults, protein-fortified food may not provide the health benefits
people expect.
Lamming notes that athletes often consume large
amounts of protein without developing metabolic diseases. He suspects
that regular exercise, perhaps by using protein to build strong
healthy muscles, helps protect them from the
negative health effects associated with a protein-rich diet.
"Recent recommendations have encouraged people to eat
more protein, but they've also encouraged people to exercise more,"
Lamming says. "We probably need to personalize protein
recommendations based not just on age, but also on how physically active people
are."
Source:
Journal reference:
The Hallmarks of Protein and Amino Acid Restriction in Aging
and Longevity. Cell Press Blue.
DOI: 10.1016/j.cpblue.2026.100079. https://www.cell.com/cell-press-blue/fulltext/S3051-3839(26)00077-0
