The protein danger? A new study determines that excessive consumption shortens life expectancy
A large-scale review of more than 350 studies found that for people who lead a sedentary lifestyle, reduced protein consumption may improve metabolism and reduce cellular damage. The researchers also point to a hormone whose level rises when consuming less protein and is linked to longevity. However, they emphasize that athletes, pregnant women, and certain older adults may actually need more protein.
Supermarket shelves are currently packed with protein-enriched products - from breakfast cereals and yogurts to coffee and even water. However, a large-scale scientific review, which examined more than 350 studies on the link between protein consumption and aging, raises a surprising possibility: for many people, and especially those who lead a sedentary lifestyle, a reduction in protein consumption may actually contribute to better health and even longevity.
The review, published in the journal Cell Press Blue, found that reduced protein consumption was linked to an improvement in metabolism, a reduction in cellular damage, and changes in the way cells respond to nutrients and maintain proper function.
"It is absolutely clear that protein has benefits in building muscle and responding to training in active people," said Prof. Dudley Lamming of the University of Wisconsin-Madison, the co-researcher of the article. "But since most people lead a relatively sedentary lifestyle, many are likely consuming more protein than they actually need, and this likely has negative health consequences."
An alternative to calorie restriction
Calorie restriction has been known for years as a factor that may extend life in a variety of organisms and reduce the risk of diseases associated with aging, but for most people, it is very difficult to maintain such a diet over time.
Protein restriction may offer an alternative. Previous studies have shown that flies and rodents lived longer when they consumed less protein, even without a decrease in total calorie consumption. In clinical trials in humans, protein reduction was linked to weight loss and a decrease in body fat percentage, and to an improvement in fasting blood sugar levels, even though in some cases the participants consumed more calories in total.
However, the picture is not unequivocal. Other studies have found that higher protein consumption may help in weight loss and in maintaining muscle mass in older adults, especially in combination with physical activity. These findings contributed to the update of the dietary guidelines in the USA this year, which recommend 1.2 to 1.6 grams of protein per kilogram of body weight per day - almost twice the amount recommended in the past.
The hormone linked to longevity
One of the central mechanisms that the review points to is related to the hormone FGF21, whose level rises when protein consumption decreases. The hormone may increase energy expenditure, improve blood sugar regulation, and reduce inflammatory processes.
Studies in mice have shown that animals whose FGF21 levels were high lived longer than regular mice, with the effect being stronger in males. It was also found in humans that reducing protein consumption raises the hormone's levels.
The review also focuses on the amino acids methionine, isoleucine, and valine. According to the studies, their excessive consumption may activate biological pathways that promote growth, and when these pathways remain active over time, they may increase the risk of obesity, inflammation, and other conditions associated with aging.
"These studies show that the amount of protein that sedentary people consume today may have negative health consequences, at least at the population level," said Lamming.
Not everyone needs the same amount
The researchers emphasize that this is not a sweeping recommendation to reduce protein. Pregnant women and older adults may need higher amounts, and athletes can also consume large amounts of protein without developing metabolic diseases.
According to Lamming, regular physical activity may protect against some of the negative effects by directing the protein to the building and maintenance of healthy muscle.
"The latest recommendations encouraged people to eat more protein, but they also encouraged them to exercise more," he said. "We probably need to customize the recommendations for protein consumption, not only by age but also by the person's level of physical activity."
