WASHINGTON, DC — Protein is everywhere right now, from fortified snacks to drinks and even water. But a new scientific review argues that more is not automatically better, and in some cases, eating less protein could help with health and longevity.
The findings add a twist to a popular nutrition trend that has been pushed in the United States, where federal dietary advice released in January 2026 encouraged people to put “protein at every meal.”
1. A new review examined 350 protein studies
The review, published July 31 in the journal Cell Press Blue, pulled together 350 studies on protein-restricted diets in animals and people. Its authors say the evidence points in a surprising direction: less protein was repeatedly linked with longer and healthier lives in several species.
That pattern showed up in mice, rats, flies, and fish. In small human studies, people on lower-protein diets for several weeks lost weight and fat mass, and their fasting blood sugar improved, even when they were eating more total calories.
2. The human diets were lower, but not extreme
The diets used in the human studies were usually not the very low-protein regimens seen in animal experiments. Instead, they generally fell within the range of the official recommended dietary allowance, or RDA, for protein.
That matters because the new U.S. dietary guidelines recommend 1.2 to 1.6 grams of protein per kilogram of body weight each day, which can be as much as twice the minimum RDA. The review suggests that hitting the RDA, rather than pushing far above it, may be enough for some health benefits.
3. Higher-protein diets do have supporters
The review also runs into research that points the other way. Some studies have found that higher-protein diets can help with weight loss, lower the risk of sarcopenia, and support a longer period of good health, often called health span.
Dudley Lamming, a University of Wisconsin-Madison professor of medicine and one of the review’s authors, said that tension is part of what makes the topic so interesting. Protein can promote fullness and support muscles, but some epidemiological studies have linked higher protein diets with higher rates of cancer, diabetes, cardiovascular disease, and even mortality.
4. One twin study pointed in the opposite direction
Lamming also cited a 2023 study of about 1,500 pairs of British twins. In that research, the sibling who ate more protein had a higher risk of developing sarcopenia than the twin who ate less.
He described that result as the opposite of what many people would expect from a nutrient so closely tied to muscle. It is one reason scientists say the relationship between protein, aging, and strength is more complicated than simple slogans about “more protein” suggest.
5. The theory is that the body shifts into repair mode
Researchers do not yet know exactly why protein restriction seems to help in animals and possibly in people. One idea is that lower protein intake pushes cells away from a growth-and-proliferation state and toward recycling and repair.
Lamming said cell division can increase the chance of mistakes when DNA is copied, and those errors can contribute to aging and disease. Under this theory, limiting protein may slow that churn and give the body more room to maintain existing cells instead of constantly making new ones.
6. Calories and protein are not the same thing
Protein restriction is often discussed alongside calorie restriction, but the two are not interchangeable. Calorie restriction is widely seen as the gold standard for extending lifespan in lab animals, yet Lamming said it is notoriously hard for people to sustain.
Some protein-restriction studies found people ate more calories, not fewer. In mice, one possible explanation is an increase in thermogenic fat, which burns energy to make heat. In that scenario, higher energy expenditure may offset the extra calories.
7. People probably do not all need the same amount
Experts quoted in the review stressed that people should not rush into very low-protein diets. Christopher D. Morrison of Louisiana State University’s Pennington Biomedical Research Center said animal studies do not guarantee the same effect in humans, and the human trials so far have been small and short-term.
Researchers also say protein needs may differ by age and activity. Lamming suggested that resistance trainers and pregnant women may benefit from more protein, while Matt Kaeberlein said very low intake could bring downsides such as poorer immune function and lower bone density.
8. The type of protein may matter as much as the amount
Not all protein appears to behave the same way. Andres V. Ardisson Korat of Tufts University, who led a 2024 study on healthier aging, said people who ate more plant-based protein were less likely to develop chronic disease and had better physical and cognitive health.
By contrast, higher animal-protein intake was linked with a higher risk of chronic disease, though it was also associated with better physical function than very low protein intake overall. The review also notes that even individual amino acids may affect health differently, but that work is still too early for personal supplement plans.
9. For now, the safest advice is still simple
Kaeberlein said scientists are still far from being able to say exactly how much protein is ideal for the population, or for any one person. Long-term data are not strong enough to support a precise grams-per-pound rule for everyone.
His practical advice is to focus first on overall diet quality: whole foods, plenty of vegetables, and a plan that fits your goals and life stage. The big picture, researchers say, is that protein is important, but more of it is not automatically the answer.
