Play store
Cutting back on protein intake could offer unexpected health benefits, including improved metabolism and slower biological ageing, according to a major scientific review that challenges the growing popularity of high-protein diets.
Researchers who examined more than 350 scientific papers found evidence that reducing protein consumption may influence several biological processes linked to ageing, cellular health and longevity. Some animal studies have also shown that protein restriction can extend lifespan without reducing overall calorie intake.
The findings, published in the Cell Press journal Cell Press Blue, raise questions about whether many people, particularly those with sedentary lifestyles, consume more protein than their bodies actually need.
“It’s absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals,” said Dudley Lamming, the study’s corresponding author at 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,” he added.
Scientists have long known that calorie restriction can extend lifespan in several organisms and reduce the risk of age-related diseases, including cancer. However, maintaining a low-calorie diet over a long period can be difficult.
Reducing protein intake without necessarily cutting total food consumption has emerged as a possible alternative.
Experiments involving flies and rodents have found that limiting protein can extend lifespan even when overall calorie intake remains unchanged. This suggests that the type of nutrients consumed, rather than simply the amount of food, may play an important role in determining longevity.
Human studies have also produced encouraging results. Several clinical trials have found that reducing protein intake can help people lose weight, lower body fat and improve fasting blood sugar levels, even when their overall calorie consumption increases.
However, researchers caution that these findings do not establish that eating less protein extends human lifespan.
The relationship between protein intake and health is also complicated by the importance of maintaining muscle mass, particularly among older adults.
Studies have shown that higher protein consumption can support weight loss and help older people preserve muscle, especially when combined with regular physical activity. Muscle loss with age can lead to weakness, reduced mobility and an increased risk of falls.
Recent changes to US dietary recommendations have encouraged daily protein consumption of 1.2 to 1.6 grams per kilogram of body weight, nearly twice the previous recommended amount.
Against this backdrop, Lamming and a colleague reviewed decades of research to better understand how protein consumption affects ageing and metabolism.
One key mechanism identified in the review involves fibroblast growth factor 21 (FGF21), a hormone whose levels increase when dietary protein is restricted.
FGF21 helps the body respond to changes in nutrient availability and regulates energy use. Higher levels of the hormone have been associated with increased energy expenditure, better blood sugar regulation and reduced inflammation.
These effects may be important because metabolic disturbances and chronic inflammation are closely linked to ageing and diseases such as obesity and diabetes.
The researchers said a better understanding of how protein intake affects these biological pathways could help develop dietary strategies to improve long-term health.
However, the findings do not suggest that everyone should reduce protein consumption. The amount needed may vary depending on age, physical activity, muscle health and individual nutritional requirements.