关键词: 膳食蛋白质类, 骨骼肌, 老年人, 横断面研究, 影响因素分析

Abstract: Background　Dietary protein intake and distribution in each meal have received increasing interest.An even distribution of protein intake throughout the day in meals can maximally stimulate muscle protein synthesis to maintain or increase muscle mass.This would be a particularly important strategy for older individuals experiencing sarcopenia and obese individuals losing skeletal muscle mass during energy-restricted diets.Objective　To investigate the correlation of daily dietary protein intake and distribution with skeletal muscle mass in community-dwelling elderly people in Shanghai.Methods　In 2017，a total of 329 elderly people were recruited from four communities（Shimenerlu Community，Chuncheng Community，Lvdi Community and Jiangsulu Community） in Shanghai.General personal characteristics were collected，including sex，age，BMI，skeletal muscle mass，body fat content and history of disease.Three-day food record was used to assess the daily dietary energy，relative daily protein intake，and daily fat intake in three consecutive days.Dietary nutrient intakes were calculated using SY nutrition software developed by Shanghai Clinical Nutrition Quality Control Center & Shanghai Medical College，Fudan University.Results　Among the 329 subjects，116 were males，and 213 were females.The mean age was（69.8±6.4） years.All of them returned effective questionnaires，with a response rate of 100.0%.Compared with women，men had higher average dietary energy，fat intake and carbohydrate intake（P<0.05）．Of the subjects，7.0%（23/329） at least consumed 2 meals of ≥30 g protein/meal，21.6%（71/329） consumed 1 meal of ≥30 g protein/meal，71.4%（235/329） did not consume any meals of ≥30 g protein/meal per day.The frequency of protein consumption（≥30 g/meal） differed significantly by BMI，skeletal muscle mass and body fat content（P<0.05）．Multiple linear regression analysis showed that having 1 meal and ≥2 meals of ≥30 g protein/meal per day instead of having no such meal were independent influencing factors of skeletal muscle mass in the elderly（P<0.05）．Sex-based subgroup analyses showed that having ≥2 meals of ≥30 g protein/meal per day was an independent influencing factor of skeletal muscle mass in elderly men（P<0.05），and having 1 meal and ≥2 meals of ≥30 g protein/meal were independent influencing factors of skeletal muscle mass in elderly women（P<0.05）．Age-based subgroup analysis found that having 1 meal and ≥2 meals of ≥30 g protein/meal per day were independent influencing factors of skeletal muscle mass in 60-79-year-old people（P<0.05）．BMI-based subgroup analysis revealed that having 1 meal and ≥2 meals of ≥30 g protein/meal per day were independent influencing factors for skeletal muscle mass in those with BMI<24 kg/m2，and those with BMI≥24 kg/m2，respectively（P<0.05）．Dose-response analysis demonstrated that when having 1 meal of 40 g protein/meal or at least 2 meals of 35 g protein/meal per day，the skeletal muscle mass tended to be stable.Conclusion　Only a few elderly people in the community consumed at least 1 meal of ≥30 g protein/meal per day.An even distribution of protein across the day in meals（≥30 g/meal） may increase or retain the skeletal muscle mass.Moreover，the consumption of 2 meals with protein content of 30-35 g per meal might be an important strategy for increasing or maintaining skeletal muscle mass in elderly people.

Key words: Dietary proteins, Skeletal, Aged, Cross-sectional studies, Root cause analysis