Independent effects of whey protein and alkali supplementation on muscle health in healthy older adults: factorial randomized controlled trial.

Ceglia Lisa, Konieczynski Elsa, Danico Elise, Trinquart Ludovic et al. — The American journal of clinical nutrition

Abstract

BACKGROUND: Aging is accompanied by reduced muscle protein synthesis and increased circulating acid, both of which contribute to declines in muscle health. OBJECTIVES: To determine the effects of whey protein (WP) and alkali (potassium bicarbonate, KHCO) supplementation on muscle performance and mass in healthy older adults. METHODS: In this randomized, 2 × 2 factorial, placebo-controlled study, healthy adults aged ≥65 years were assigned to either WP (1.5 g/kg/d) plus KHCO (81 mmol/d), WP plus placebo-KHCO, placebo-WP plus KHCO, or double placebo. Double leg press muscle power (primary outcome), physical performance, lean mass by dual energy x-ray absorptiometry, muscle mass by D-creatine dilution, and serum insulin-like growth factor 1 (IGF-1) were measured at baseline and 24 weeks. Primary analyses estimated main effects of WP compared with placebo-WP and KHCO compared with placebo-KHCO using factorial comparisons "at-the-margins," following CONSORT/SPIRIT recommendations for factorial trials. Between-group differences in the 24-wk outcomes were estimated using analysis of covariance adjusted for baseline value, age, and sex. RESULTS: In the intention-to-treat sample (n = 128), 47.7% were female, mean ± SD age was 74 ± 6 y, and baseline protein intake was 0.85 ± 0.30 g/kg/d. Neither WP nor KHCO affected muscle power compared with their respective placebo {WP to placebo-WP difference 4.7 watts [95% confidence interval (CI): -21.1,30.5; P = 0.72]; KHCO to placebo-KHCO difference -13.6 watts [95% CI: -39.6, 12.4; P = 0.30]}. No group differences were noted in physical performance or muscle mass. However, 24-wk mean IGF-1 level was higher in the WP and KHCO groups compared with their respective placebo [WP to placebo-WP difference 14.2 ng/mL (95% CI: 7.5, 21.0; P < 0.01); KHCO to placebo-KHCO difference 7.2 ng/mL (95% CI: 0.4, 13.9; P = 0.04)]. CONCLUSIONS: In healthy free-living older adults reporting a protein intake at the current recommended daily allowance, neither increasing protein to 1.5 g/kg/d with WP nor adding a KHCO supplement for 24 wk improved measures of muscle power, physical performance, or muscle mass despite achieving higher circulating IGF-1 levels. CLINICAL TRIAL REGISTRY NUMBER: This trial was registered as NCT04048616 at https://clinicaltrials.gov/study/NCT04048616?term=ceglia&rank=1.

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