The Effects of Ingesting a Single Bolus of Hydrolyzed Collagen versus Free Amino Acids on Muscle Connective Protein Synthesis Rates.
Level 2 - randomized trial
Randomized, double-blind, placebo-controlled parallel trial
PubMed 40523226 · doi:10.1249/MSS.0000000000003788
What was done
In a double-blind parallel trial, 45 young adults (21 males, 24 females; age 23 ± 3 yr, BMI 22.3 ± 2.2 kg·m⁻²) received intravenous L-[ring-¹³C₆]-phenylalanine infusions and performed unilateral resistance exercise. Participants ingested 30 g hydrolyzed collagen (n = 15), 30 g free amino acids matching collagen's profile (n = 15), or a noncaloric placebo (n = 15). Blood and muscle biopsies were collected over 6 hours to assess myofibrillar and muscle connective protein synthesis rates.
What was found
Ingestion of collagen and free amino acids increased circulating plasma amino acids, but neither stimulated protein synthesis compared to placebo (all P > 0.05). Myofibrillar protein synthesis rates (%·h⁻¹) were 0.039 ± 0.011 (PLA), 0.037 ± 0.010 (COLL), and 0.036 ± 0.015 (AA) in the rested leg, and 0.049 ± 0.010 (PLA), 0.048 ± 0.011 (COLL), and 0.045 ± 0.013 (AA) in the exercised leg. Muscle connective protein synthesis rates (%·h⁻¹) were 0.065 ± 0.014 (PLA), 0.063 ± 0.017 (COLL), and 0.061 ± 0.025 (AA) in the rested leg, and 0.098 ± 0.023 (PLA), 0.092 ± 0.028 (COLL), and 0.085 ± 0.024 (AA) in the exercised leg.
Why it matters
Despite commercial claims that collagen supplements promote connective tissue remodeling, an acute 30 g bolus provides no additive stimulus to muscle connective or myofibrillar protein synthesis rates beyond exercise alone.
Limits
Evaluated only acute (6-hour) responses to a single bolus rather than long-term training adaptations. The sample was restricted to healthy, young, recreationally active adults, and did not evaluate tendon or ligament tissue synthesis directly.
Cited by
- supports Connective tissue protein synthesis rates increase in skeletal muscle following physical activity independently of post-exercise protein or collagen intake.