As most existing data on the association between dietary protein intake and muscle mass come from Western countries, researchers in China have conducted a cross-sectional study to investigate how different amounts and sources of protein consumption affect muscle mass in older Chinese adults.
The analysis was based on data from the China Health and Nutrition Survey (CHNS) 2018, which included 4,826 participants from 15 provinces, who are aged 60 years and above.
The protein intake data was evaluated using three-day (two weekdays and one weekend) 24-hour dietary recalls, which were obtained through face-to-face interviews with the participants.
Their appendicular skeletal muscle mass (sum of muscle masses of the four limbs) were assessed via bioelectrical impedance analysis, a method that measures body composition based on the rate at which an electrical current travels through the body.
Plant-based protein sources were defined as cereals, tubers, starches, legumes, vegetables, fruits, fungi, algae, nuts and seeds, while animal proteins were identified as meat, poultry, milk, eggs and aquatic products.
According to the findings, two-thirds of the participants’ dietary protein intake came from plant sources.
More importantly, it was found that higher levels of total dietary protein intake and plant-based protein intake were positively linked to higher muscle mass. The association between animal protein and muscle mass was insignificant.
In the group with participants who had the highest total protein intake, muscle mass increased by 0.96kg among men and 0.48kg among women.
Similarly, in the group comprising participants who had the highest plant-based protein intake, muscle mass rose by 0.76kg among men and 0.35kg among women.
In addition, the study indicated that a dietary protein intake above 78 grams of protein per day (g/d) in males and 68g/d in females could be ideal for preventing low muscle mass among the elderly population.
“The traditional Chinese diet is characterised by large amounts of cereals and vegetables. Thus, plant-protein intake contributed more to the total protein intake than animal-protein intake.
“Although animal protein is widely recognised to contain more nutritional properties than plant-based protein, the antioxidants and vitamins found in vegetables and fruits can enhance plant-protein absorption. It is also possible that consuming greater amounts of plant-based proteins can achieve the same anabolic (muscle-building) response evoked by smaller quantities of animal protein,” said the authors.
Revision of recommendations needed
Although the study participants consumed an equal amount of protein across all three meals in a day, the intake each time was less than 20g, which is below the recommended 25 to 45g for the optimal stimulation of muscle protein synthesis.
At the same time, recent studies have pointed out that current protein-intake recommendations in China are insufficient in preserving muscle mass and strength.
“Elderly individuals, men, and people with lower education and who live in rural areas are at high risk of low muscle mass. It is time to consider updating the recommendations,” said the authors.
In 2020, approximately 18.7% of the total Chinese population were aged 60 and above. Ageing is a major factor in the decline of bodily function, including skeletal muscle mass.
Specifically, sarcopenia, or the gradual loss of muscle mass, strength and function, reduces one’s ability to perform daily tasks and can affect quality of life to a large extent.
Nutrition, exercise and pharmacologic agents are the key interventions for the condition. Therefore, adequate consumption of dietary protein is critical to protect against sarcopenia.
“Relatively few studies have examined issues such as the amount and the type of dietary protein that provide the greatest benefit for muscle mass among the elderly Chinese population. Further research is needed to verify the optimal level of dietary protein intake recommended in our study,” the authors concluded.
“Association of Dietary Protein Intake with Muscle Mass in Elderly Chinese: A Cross-Sectional Study”
Authors: Yifei Ouyang, et al