Dietary protein intake positively associated with muscle mass in the elderly

In a cross-sectional study evaluating elderly Chinese adults, high total protein and plant-based protein consumption was associated with higher muscle mass.

“After adjusting for all covariates, higher levels of total dietary protein intake and vegetable protein intake were associated with higher muscle mass, showing an increasing trend (p_trend<0.05),” said the researchers.

Compared with participants with the lowest total protein intake, those with the highest total protein intake had increased muscle mass by 0.96 kg (men) and 0.48 kg (women). Similarly, increased muscle mass was observed among those with the highest vs lowest vegetable protein intake (by 0.76 kg [men] and 0.35 kg [women]; p<0.0001 for all). [Nutrients 2022;14:5130]

“[T]he traditional Chinese diet is charactered by large amounts of cereals and vegetables. Thus, plant protein intake contributed more to the total dietary protein intake than animal protein intake,” the researchers explained.

Moreover, in the spline regression model, male participants who had a daily protein intake of 78 g had a reduced risk of low muscle mass compared with their counterparts who had no dietary protein intake (odds ratio [OR], 0.38; p<0.001). A similar effect was seen among females who had a daily protein intake of 68 g (OR, 0.34; p<0.001).

These protein intake values exceed the current Chinese dietary reference intakes for older adults, such as the EAR* (60 g/day [males] and 50 g/day [females]) and RNI** (65 and 55 g/day, respectively). “[These values] might be a threshold point for preventing low muscle mass in elderly Chinese adults,” said the researchers.

Preventing muscle mass decline

A total of 4,826 elderly adults from the dataset of the China Health and Nutrition Survey (CHNS) 2018 were included in the analysis. Protein intake data were evaluated using 3-day, 24-hour dietary recalls.

Although daily protein intake was equally distributed across the three basic meals, total dietary protein intake per meal was barely 20 g, which is the minimum needed to stimulate muscle protein synthesis, the researchers noted.

“The Chinese elderly population should be encouraged to consume a moderate amount of protein to solicit a positive muscle synthesis response,” they said. Consuming about 25–40 g of protein per meal has been suggested for optimum stimulation of muscle synthesis in older individuals. [Clin Nutr 2016;35:1506-1511; J Int Soc Sports Nutr 2017;14:20]

Muscle mass decline could lead to sarcopenia and subsequently, serious issues such as frailty and increased risk of falls, fractures, and even death. [J Nutr Health Aging 2008;12:427-432; J Am Med Dir Assoc 2020;21:300-307.e2] A higher muscle mass may protect against sarcopenia. [J Nutr 2015;145:1569-1575; Am J Clin Nutr 2021;114:29-41] “[Thus,] the adequate consumption of dietary protein is critical for the maintenance of muscle mass,” said the researchers.

Updated recommendations warranted

The gap between plant and animal protein intake may eventually taper off as the Chinese diet incorporates more animal-based foods today. [Nutrients 2021;13:3806] “Our CHNS research group will follow this trend and identify the association between animal protein and mass muscle and sarcopenia in future analyses,” said the researchers.

Apart from age, the increased susceptibility of some elderly Chinese individuals to the risk of low muscle mass may also be due to factors such as education level (ie, primary education/illiteracy) and residential area (ie, those living in the villages).

“Since elderly Chinese individuals are at high risk for insufficient protein intake, it is time to consider updating the protein intake recommendation to confer muscle health,” they said, calling for further studies to validate the optimal level of dietary protein intake in this population.