Protein intake in midlife helps promote healthy ageing

Middle-aged adults who consume protein-rich foods, particularly plant protein, have a better chance of healthy ageing, including good physical function and good mental health status, suggests a study.

“Our study contributes evidence to the role of protein in the aetiology of healthy ageing and adds specific insights to the importance of protein sources and relevant aetiologic windows in midlife, which may contribute to providing recommendations regarding the amount of protein intake to promote healthy ageing,” the researchers said.

A total of 48,762 participants aged <60 years in 1984 from the Nurses’ Health Study (NHS) were included in this analysis. Validated food frequency questionnaires were used to derive protein intake information, including total protein and protein from animal, dairy, and plant sources.

Healthy ageing referred to being free from 11 major chronic diseases, having good mental health, and not having impairments in either cognitive or physical function, as assessed in the 2014 or 2016 NHS participant questionnaires.

The research team used multivariate logistic regression, with adjustments for lifestyle, demographics, and health status, to calculate the odds ratios (ORs) and 95 percent confidence interval (CIs) for protein intake in relation to healthy ageing.

Of the NHS participants, 3,721 (7.6 percent) met the definition of healthy ageing. Protein intake appeared to contribute to a higher likelihood of healthy ageing. [Am J Clin Nutr 2024;119:271-282]

The ORs per 3-percent energy increment with healthy ageing were 1.05 (95 percent CI, 1.01‒1.10) for total protein, 1.07 (95 percent CI, 1.02‒1.11) for animal protein, 1.14 (95 percent CI, 1.06‒1.23) for dairy protein, and 1.38 (95 percent CI, 1.24‒1.54) for plant protein. Plant proteins also correlated with a higher chance of having good physical function and good mental status.

Substitution analyses revealed significant positive associations for the isocaloric replacement of animal or dairy protein, carbohydrate, or fat with plant protein (ORs for healthy ageing, 1.22‒1.58 for 3-percent energy replacement with plant protein).

Mechanisms

“The mechanisms explaining the associations between protein intake and healthy ageing are complex and not fully understood,” the researchers said.

An earlier study provided evidence suggesting that the activation of the mammalian target of the rapamycin complex 1 signalling pathway decreases with age. Dietary protein and exercise activate this target, thus stimulating muscle protein synthesis, which contributes to better physical function in older adults. [Nutr Res 2017;40:1-20; J Nutr Sci Vitaminol (Tokyo) 2015;(Suppl S125–S127):61]

“There are several potential mechanisms that may explain the differential associations between plant and animal protein intake on the chronic disease domain of the healthy ageing phenotype,” according to the researchers.

“Plant protein has been associated with favourable levels of important risk factors of cardiometabolic diseases, such as reduced LDL cholesterol, lower blood pressure, and insulin sensitivity and decreased levels of proinflammatory markers,” they added. [Br J Nutr 2004;92:657-663; Annu Rev Nutr 2007;27:293-310; Prim Care Diabetes 2022;16:634-639; Diabetes Care 2022;45:1742-1753]

On the other hand, total and animal protein intake has been shown to positively correlate with concentrations of insulin-like growth factor 1, which is known to contribute to the growth of malignant cells in breast and prostate tissue. [Cancer Epidemiol Biomarkers Prev 2002;11:1441-1448; Cancer Epidemiol Biomarkers Prev 2002;11:852-861; Int J Epidemiol 2023;52:71-86]

“Future research is warranted to verify these findings in other populations and to elucidate the mechanisms underlying the associations between protein intake and healthy ageing,” the researchers said.