Essential amino acid and carbohydrate supplementation ameliorates muscle protein loss in humans during 28 days bedrest.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 15356032 · doi:10.1210/jc.2003-032159
What was done
Participants underwent 28 days of bed rest and were assigned to a control group receiving standard nutritionally mixed meals every 5 hours or an experimental group receiving the standard diet supplemented with 16.5 g of essential amino acids and 30 g of carbohydrate three times daily (at 1100, 1600, and 2100 h). On days 1 and 28, mixed muscle fractional synthetic rate (FSR), phenylalanine net balance, lean leg mass, and leg extension strength were evaluated during a 16-hour tracer infusion using vastus lateralis muscle biopsies and femoral arterio-venous blood sampling.
What was found
Muscle fractional synthetic rate was higher in the supplement group on day 1 (0.099 ± 0.008%/h vs. 0.075 ± 0.005%/h in controls) and day 28 (0.093 ± 0.006%/h vs. 0.055 ± 0.007%/h). Lean leg mass was maintained in the supplement group (+0.2 ± 0.3 kg) but decreased in controls (-0.4 ± 0.1 kg). Leg extension strength decreased in both groups, but the loss was smaller with supplementation (-8.8 ± 1.4 kg vs. -17.8 ± 4.4 kg in controls).
Why it matters
This study demonstrates that targeted essential amino acid and carbohydrate supplementation can preserve lean mass and attenuate muscle wasting and weakness caused by prolonged disuse.
Limits
The abstract does not state the total sample size, participant demographics (such as age or sex), or p-values. Phenylalanine net balance values are mentioned as an outcome but specific numerical results are omitted.
Cited by
- supports NASA-sponsored bed rest studies at the University of Texas Medical Branch found that subjects placed on complete bed rest for 28 days at maintenance calories had no average muscle loss when supplemented with leucine-enriched essential amino acids.