Intake of low-dose leucine-rich essential amino acids stimulates muscle anabolism equivalently to bolus whey protein in older women at rest and after exercise.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 25827594 · doi:10.1152/ajpendo.00481.2014
What was done
Sixteen older women (mean age 66 ± 2.5 years; n = 8 per group) were randomized to receive either 20 g of bolus whey protein (WP) or 3 g of leucine-enriched essential amino acids (LEAA, 40% leucine). Using [13C6]phenylalanine infusions, muscle protein synthesis (MPS) and albumin protein synthesis (APS) were quantified at baseline, after feeding alone (FED), and after feeding plus exercise (FED-EX; 6 × 8 knee extensions at 75% 1-repetition maximum). Plasma insulin and amino acid concentrations, leg blood flow (LBF), muscle microvascular blood flow (MBF), and intramuscular anabolic signaling were also measured.
What was found
Plasma insulin and essential amino acid concentrations were significantly greater after WP than LEAA (P < 0.001). LBF did not change in either group, but MBF increased similarly in both groups only after FED-EX (P < 0.05). Following FED alone, MPS increased similarly in both groups from 0–2 hours (P < 0.05) and abated by 0–4 hours (P > 0.05). Following FED-EX, MPS increased from 0–2 hours and remained elevated at 0–4 hours (P < 0.05) equally in both groups. p70 S6K1 Thr389 phosphorylation increased only after FED-EX at 2 hours (P < 0.05). APS increased similarly in both groups.
Why it matters
Low-dose leucine-enriched essential amino acids can elicit the same acute muscle protein synthesis response as a much larger bolus of intact whey protein in older women. This provides an efficient nutritional strategy for supporting muscle maintenance in populations with reduced appetite or anabolic resistance.
Limits
The study had a small sample size (n = 8 per group) and included only older women. Measurements were limited to acute 4-hour postprandial fractional synthetic rates, so long-term effects on muscle mass, strength, and clinical sarcopenia outcomes were not evaluated.
Cited by
- supports In 60-year-old women, consuming 3 grams of essential amino acids containing 40% leucine stimulates as much muscle protein synthesis as 20 grams of whey protein.