Relation between mealtime distribution of protein intake and lean mass loss in free-living older adults of the NuAge study.
Level 3 - non-randomized controlled study
Prospective observational cohort study
PubMed 27465379 · doi:10.3945/ajcn.116.130716
What was done
Researchers evaluated 712 community-dwelling older adults (351 men, 361 women, aged 67–84 years) from the Quebec Longitudinal Study on Nutrition as a Determinant of Successful Aging (NuAge). Body composition was measured via dual-energy X-ray absorptiometry (DXA) at baseline and after 2 years. Diet was assessed using three 24-hour recalls at baseline and three at follow-up. Protein distribution across meals was calculated as the coefficient of variation (CV) of protein ingested per meal. Linear mixed models adjusted for covariates evaluated changes in total lean mass (LM) and appendicular lean mass (aLM).
What was found
Over 2 years, total lean mass significantly declined in both men (-2.5% ± 4.0%) and women (-2.0% ± 3.4%) (P < 0.05), whereas appendicular lean mass loss did not reach significance (men: -1.5% ± 4.8%; women: -1.2% ± 5.3%; P > 0.05). The rate of lean mass decline was not independently affected by protein quantity or meal distribution. However, individuals with evenly distributed protein intakes (both sexes) and men with higher total protein intake maintained significantly higher overall LM or aLM throughout the 2-year period after adjusting for confounders (P < 0.05).
Why it matters
While short-term metabolic studies show that an even protein distribution enhances muscle protein synthesis, these observational results indicate that even distribution correlates with higher overall muscle mass but does not alter the rate of age-related muscle loss over 2 years.
Limits
The observational design cannot establish causality. Dietary intake was self-reported via 24-hour recalls, introducing recall and reporting bias. The 2-year follow-up period may be too short to detect modest differences in rates of muscle wasting. Functional strength and physical activity levels were not reported in the abstract.
Cited by
- supports Longitudinal research indicates that spreading protein intake across at least three or four relatively spaced meals per day leads to better protein utilization.