Daily Supplementation With Whey, Soy, or Whey-Soy Blended Protein for 6 Months Maintained Lean Muscle Mass and Physical Performance in Older Adults With Low Lean Mass

Background: Few studies have investigated the effect of long-term protein supplementation alone on muscle health in older adults with low lean mass.

Objective: To determine the effect of whey, soy or whey-soy blended protein supplementation on lean muscle mass and physical performance in older adults with low lean mass.

Design: A 4-arm randomized controlled trial.

Participants/setting: Chinese older adults (n = 123, 65-79 years) with low lean mass (appendicular skeletal muscle index < 7.0 kg/m² in men and < 5.4 kg/m² in women) living in the urban area of Guangzhou participated between October 2015 and June 2016.

Intervention: Participants were randomly assigned to receive approximately 16 g/d of whey, soy, or whey-soy blend protein or maintained habitual diets in control group for 6 months.

Main outcome measures: Lean mass, handgrip strength, and physical performance (gait speed, chair stand test, and Short Physical Performance Battery) were assessed at baseline and 6 months.

Statistical analyses: Two-way analysis of variance with the main effects of treatment and time and treatment × time interaction and analysis of covariance was used to determine differences in outcomes.

Results: Appendicular skeletal muscle index, lean mass, percent lean mass in legs and appendicular areas, gait speed, and Short Physical Performance Battery score were maintained in the treatment groups and decreased in the control group, resulting in significant reduction in these variables from baseline in the control compared with treatment groups (all P < .01; percent differences between treatment and control groups ranged from 80% to 156%). The chair stand test time at month 6 decreased from baseline in the treatment groups and increased in the control group, resulting in a significant increase in the control compared with treatment groups (all P < .01; percent differences between treatment and control groups ranged from 132% to 155%). Handgrip strength remained unchanged. There were no significant differences in outcomes among treatment groups.

Conclusions: Supplementation with whey, soy, or whey-soy blended protein for 6 months equally maintained lean muscle mass and physical performance in older adults with low lean mass.