Coingestion of Collagen With Whey Protein Prevents Postexercise Decline in Plasma Glycine Availability in Recreationally Active Men.
Level 2 - randomized trial
Randomized, double-blind, crossover trial in humans
PubMed 38604602 · doi:10.1123/ijsnem.2023-0264
What was done
In a randomized, double-blind, crossover trial, 14 recreationally active men (age 26 ± 5 years, BMI 23.8 ± 2.1 kg·m-2) ingested 30 g total protein immediately after a single bout of lower body resistance exercise across four conditions: whey alone (WHEY), whey with 5 g collagen (WC05), whey with 10 g collagen (WC10), and whey with 15 g collagen (WC15). Blood samples were collected frequently over 6 hours of postexercise recovery to measure plasma amino acid kinetics and availability.
What was found
Total plasma amino acid concentrations increased after ingestion across all conditions (p < .001) with no difference in total amino acid availability between treatments (p > .05). Leucine and essential amino acid availability were significantly higher in WHEY compared to WC10 and WC15 (p < .05). Plasma glycine and nonessential amino acid concentrations declined following WHEY alone but increased with collagen coingestion (p < .05). Postprandial plasma glycine availability (incremental area under the curve) was -8.9 ± 5.8 mmol·360 min/L in WHEY, 9.2 ± 3.7 mmol·360 min/L in WC05, 23.1 ± 6.5 mmol·360 min/L in WC10, and 39.8 ± 11.0 mmol·360 min/L in WC15 (p < .05).
Why it matters
Coingesting as little as 5 g of collagen with 25 g of whey protein prevents the postexercise decline in plasma glycine availability. This identifies a simple nutritional strategy to sustain circulating glycine availability for connective tissue recovery without fully sacrificing essential amino acid delivery.
Limits
The study was conducted in a small sample of 14 young, recreationally active men, limiting generalizability to women, older adults, or athletes. It measured acute (6-hour) circulating amino acid concentrations rather than direct rates of muscle connective protein synthesis, collagen synthesis, or long-term clinical outcomes.
Cited by
- supports Connective tissue protein synthesis rates increase in skeletal muscle following physical activity independently of post-exercise protein or collagen intake.