Two reports in Cell Metabolism suggest that the protein composition of the diet has a strong effect on healthspan.
Samantha M. Solon-Biet and her colleagues (Cell Metab. 19, 418–430, 2014 ) explored the effects of 25 different ad libitum diets on the lifespan and cardiometabolic phenotypes of mice. The 25 diets varied by protein, carbohydrate and fat content, as well as by energy density. Mice fed diets relatively low in protein and high in carbohydrates lived longer and had better metabolic health than those on a higher protein, lower carb diet.
The study by Levine et al. (Cell Metab. 19, 407–417, 2014) examined data from 6,831 individuals from the US National Health and Nutrition Examination Survey (NHANES) III study. A self-reported low-protein diet was found to be associated with lower overall, cancer-related and diabetes-related mortalities. This was only true for people between the ages of 50 and 65 when the study was started. For those aged 65 or older when first surveyed, a high-protein diet (especially from plants) was found to be more protective for such mortalities. The authors' data suggests that lower insulin-like growth factor-1 signaling explains these beneficial effects in the younger cohort. They also hypothesize that older people have a harder time absorbing protein, leading to frailty, so a low-protein diet exacerbates this condition.
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Levinson, R. Dietary protein and lifespan. Nat Med 20, 349 (2014). https://doi.org/10.1038/nm.3537