Relation between mealtime distribution of protein intake and lean mass loss in free-living older adults of the NuAge study

Background: Studies have shown that an even protein intake distribution across meals increased 24-h muscle protein synthesis in young adults compared with a skewed intake. Whether this short-term result translates into long-term preservation of lean mass (LM) in older adults remains unknown. Objective: The aim was to examine the extent to which protein quantity and distribution are associated with LM and appendicular LM (aLM), and their 2-y decline, in community-dwelling older adults. Design: Baseline and 2-y follow-up data from 351 men and 361 women (aged 67-84 y) in the NuAge study (Quebec Longitudinal Study on Nutrition as a Determinant of Successful Aging) with available body-composition data (by dual-energy X-ray absorptiometry) were used. Food intake was assessed with the use of three 24-h food recalls collected at baseline and 3 collected at the 2-y follow-up. Protein distribution across meals was calculated as the CV of protein ingested per meal, with lower values reflecting evenness of protein intake. Linear mixed-model analysis was performed to examine changes in LM and aLM across time, by sex, as conditioned by the quantity and distribution of protein intake, adjusted for potential covariates. Results: Over 2 y, LM declined in both men (-2.5% +/- 4.0%) and women (-2.0% +/- 3.4%) (P < 0.05), whereas aLM loss was not significant (men: -1.5% +/- 4.8%; women: -1.2% +/- 5.3%; P > 0.05). The decline in LM was not independently affected by the quantity and distribution of protein intake. Yet men and women with evenly distributed protein intakes and men with high protein intakes showed higher LM or aLM throughout the entire follow-up period, even after potential confounders were controlled for (P < 0.05). Conclusions: Our results suggest that greater protein intakes and a more even distribution across meals are modifiable factors associated with higher muscle mass in older adults but not with losses over 2 y. Interventional studies should determine longer-term effects on preserving LM with aging.