Dietary proteins and amino acids in the control of the muscle mass during immobilization and aging: role of the MPS response.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing mechanistic and preliminary clinical literature without systematic search methodology.
PubMed 28175999 · doi:10.1007/s00726-017-2390-9
What was done
This narrative review synthesized literature examining how dietary proteins, essential amino acids (EAAs), and leucine ingestion influence postprandial muscle protein synthesis (MPS) and muscle mass retention during immobilization, bed rest, and aging, as well as the impact of inflammation and oxidative stress on anabolic resistance.
What was found
The abstract reports no quantitative data or effect sizes. It qualitatively reports that acute ingestion of EAAs and dietary protein rich in leucine can restore postprandial MPS in disuse and aging states, but chronic trials of free leucine supplementation show conflicting results regarding muscle mass retention. Increasing total dietary protein appears more effective than isolated leucine supplementation for preserving lean mass. In addition, blunted MPS driven by oxidative and inflammatory stress is highlighted as a major driver of muscle loss, with preliminary work indicating that co-ingestion of antioxidant compounds may help restore anabolic sensitivity.
Why it matters
This review emphasizes that acute postprandial MPS improvements do not automatically produce long-term muscle preservation in catabolic states. It underscores the need to address underlying anabolic resistance and systemic inflammation alongside total protein intake.
Limits
The paper is a non-systematic narrative review providing no quantitative metrics, trial numbers, or participant counts in the abstract. The abstract notes that evidence for chronic lean mass preservation from specific supplementation strategies remains equivocal and optimal protein dosing and timing are not yet established.
Cited by
- supports Older adults require a higher amount of leucine per serving (around 2.5 grams or more) to trigger muscle protein synthesis due to anabolic resistance.