Effects of Low-Dose Dairy Protein Plus Micronutrient Supplementation during Resistance Exercise on Muscle Mass and Physical Performance in Older Adults: A Randomized, Controlled Trial.

Abstract

To investigate whether supplementation with low-dose dairy protein plus micronutrients augments the effects of resistance exercise (RE) on muscle mass and physical performance compared with RE alone among older adults. Randomized controlled trial. Tokyo, Japan. Eighty-two community-dwelling older adults (mean age, 73.5 years) were randomly allocated to an RE plus dairy protein and micronutrient supplementation group or an RE only group (n = 41 each). The RE plus supplementation group participants ingested supplements with dairy protein (10.5 g/day) and micronutrients (8.0 mg zinc, 12 μg vitamin B12, 200 μg folic acid, 200 IU vitamin D, and others/day). Both groups performed the same twice-weekly RE program for 12 weeks. Whole-body, appendicular, and leg lean soft-tissue mass (WBLM, ALM, and LLM, respectively) with dual-energy X-ray absorptiometry, physical performance, biochemical characteristics, nutritional intake, and physical activity were measured before and after the intervention. Data were analyzed by using linear mixed-effects models. The groups exhibited similar significant improvements in maximum gait speed, Timed Up-and-Go, and 5-repetition and 30-s chair stand tests. As compared with RE only, RE plus supplementation significantly increased WBLM (0.63 kg, 95% confidence interval [CI]: 0.31-0.95), ALM (0.37 kg, 95% CI: 0.16-0.58), LLM (0.27 kg, 95% CI: 0.10-0.46), and serum concentrations of 25-hydroxyvitamin D (4.7 ng/mL, 95% CI: 1.6-7.9), vitamin B12 (72.4 pg/mL, 95% CI: 12.9-131.9), and folic acid (12.9 ng/mL, 95% CI: 10.3-15.5) (all P < 0.05 for group-by-time interactions). Changes over time in physical activity and nutritional intake excluding the supplemented nutrients were similar between groups. Low-dose dairy protein plus micronutrient supplementation during RE significantly increased muscle mass in older adults but did not further improve physical performance.