A randomized controlled trial of the impact of protein supplementation on leg lean mass and integrated muscle protein synthesis during inactivity and energy restriction in older persons

https://doi.org/10.1093/ajcn/nqy193Get rights and content
Under an Elsevier user license
open archive

ABSTRACT

Background

In older persons, muscle loss is accelerated during physical inactivity and hypoenergetic states, both of which are features of hospitalization. Protein supplementation may represent a strategy to offset the loss of muscle during inactivity, and enhance recovery on resumption of activity.

Objective

We aimed to determine if protein supplementation, with proteins of substantially different quality, would alleviate the loss of lean mass by augmenting muscle protein synthesis (MPS) while inactive during a hypoenergetic state.

Design

Participants (16 men, mean ± SD age: 69 ± 3 y; 15 women, mean ± SD age: 68 ± 4 y) consumed a diet containing 1.6 g protein · kg–1 · d–1, with 55% ± 9% of protein from foods and 45% ± 9% from supplements, namely, whey protein (WP) or collagen peptides (CP): 30 g each, consumed 2 times/d. Participants were in energy balance (EB) for 1 wk, then began a period of energy restriction (ER; –500 kcal/d) for 1 wk, followed by ER with step reduction (ER + SR; <750 steps/d) for 2 wk, before a return to habitual activity in recovery (RC) for 1 wk.

Results

There were significant reductions in leg lean mass (LLM) from EB to ER, and from ER to ER + SR in both groups (P < 0.001) with no differences between WP and CP or when comparing the change from phase to phase. During RC, LLM increased from ER + SR, but in the WP group only. Rates of integrated muscle protein synthesis decreased during ER and ER + SR in both groups (P < 0.01), but increased during RC only in the WP group (P = 0.05).

Conclusions

Protein supplementation did not confer a benefit in protecting LLM, but only supplemental WP augmented LLM and muscle protein synthesis during recovery from inactivity and a hypoenergetic state. This trial was registered at http://www.clinicaltrials.gov as NCT03285737.

Key Words

muscle protein synthesis
older adults
whey protein
collagen peptides
step reduction

Abbreviations used

APE
atomic percentage excess
CP
collagen peptide
CRP
C-reactive protein
CSA
cross-sectional area
DXA
dual-energy X-ray absorptiometry
EAA
essential amino acid
EB
energy balance phase
ER
energy-restricted phase
ER + SR
energy-restricted and step-reduction phase
LBM
lean body mass
LLM
leg lean mass
MPS
muscle protein synthesis
PASE
physical activity scale for the elderly
RC
recovery phase
RDA
Recommended Dietary Allowance
SR
step reduction
WP
whey protein

Cited by (0)

Funding for this study was provided by the Whey Protein Research Consortium and the US National Dairy Council.