Scientists discover benefits of a moderate-protein diet for improved metabolic health, paving the way for potential nutritional interventions.

It all comes down to diet and exercise, right? We know that proper nutrition plays a crucial role in maintaining metabolic health and promoting longevity, and the food we consume directly impacts our well-being throughout our lives. There is a direct link between the nutritional requirements associated with aging and metabolic health, and research has demonstrated the positive effects of protein intake modifications on the health and longevity of rodents and primates – but just how much protein should be included in our diets to achieve these benefits? To answer this question, a team of researchers from Japan conducted a study using young and middle-aged male mice.

Longevity.Technology: Diet has long been recognized as a crucial factor in promoting longevity and improving overall health. Numerous studies have shown that caloric restriction, which involves reducing calorie intake without malnutrition, can extend lifespan and delay age-related diseases in various organisms, including yeast, worms, flies and mammals. Similarly, intermittent fasting, which involves alternating periods of fasting and eating, has been shown to have beneficial effects on lifespan and metabolic health.

In addition, studies have also highlighted the association between dietary macronutrients (proteins, carbohydrates, fats) and cardio-metabolic health and aging in mice. However, the specific protein intake required to maintain metabolic health had been uncertain.

In a recent study published in GeroScience, researchers from Waseda University in Japan, explored the impact of dietary protein on metabolic health in mice approaching old age.

The researchers selected young (6 months old) and middle-aged (16 months old) male C57BL/6NCr mice and fed them isocaloric diets containing varying protein contents ranging from 5% to 45% for a duration of two months. To assess the effects of different protein diets, the team measured factors such as skeletal muscle weight, liver and plasma lipid profiles, and conducted a self-organizing map (SOM) cluster analysis of plasma amino acid profiles [1].

Assistant Professor Yoshitaka Kondo, who led the research, explained that the optimal balance of macronutrients for ideal health outcomes may vary across different life stages.

“Previous studies show the possibility of minimizing age-specific mortality throughout life by changing the ratio of dietary protein to carbohydrates during the approach to old age in mice,” he said. “However, the amount of protein that should be consumed to maintain metabolic health while approaching old age is still unclear [2].”

The results of the study revealed that mice fed a low-protein diet developed mild fatty liver, exhibiting higher levels of hepatic lipids in middle-aged mice compared to their younger counterparts. In contrast, the mice on a moderate-protein diet displayed reduced blood glucose concentrations and lipid levels in both the liver and plasma. These findings indicate that a moderate-protein diet, specifically containing 25% and 35% protein, supported better metabolic health in both young and middle-aged mice [1].

Further analysis of plasma amino acid concentrations in mice of different age groups, subjected to varying protein diets, revealed that the levels of individual amino acids varied with age and dietary protein content. This finding was further supported by the self-organizing map (SOM) analysis of plasma amino acid profiles. Additionally, the SOM analysis highlighted the correlation between protein intake and levels of hepatic triglycerides and cholesterol [1].

The research team feel their study has implications for public health. Kondo commented: “Protein requirements change through the course of life, being higher in younger reproductive mice, reducing through middle age, and rising again in older mice as protein efficiency declines. The same pattern is likely to be observed in humans. Therefore, it could be assumed that increasing daily protein intake in meals could promote metabolic health of people. Moreover, ideal dietary macronutrient balance at each life stage could also extend health span [2].”

Maintaining a balanced diet that includes moderate amounts of protein could be the key to a long and healthy life. Uncovering the relationship between protein intake and metabolic health could lead to strategies for developing nutritional interventions and improving overall well-being in humans.

[1] https://link.springer.com/article/10.1007/s11357-023-00797-3
[2] https://www.waseda.jp/top/en/news/77950