Table 4.

Studies assessing the effects of collagen supplementation on collagen synthesis and muscle protein synthesis

Study	QACIS score	Participants	Type and dosage	Exercise modality	Outcome measures	Main findings
Shaw et al. (2017)	91.67%	8 recreationally active men (27 ± 6 years)	5 or 15 g/day of vitamin C enriched gelatine	6 min of rope-skipping 3 times a day for 3 days	Engineered ligaments were used to analyse the functional effect of COL	↑ in collagen synthesis with 15 g COL (153% from baseline, p < 0.05) vs 5 g/day gelatine group (59.2%) and PLA (53.9%)
Lis and Baar (2019)	71.43%	10 recreationally active men (23 ± 5 years)	15 g/day collagen hydrolysate or gelatine or gummy containing both	6 min jump rope	Blood samples to assess collagen synthesis	COL may improve collagen synthesis when taken 1 h prior to exercise. But large variability in results led no statistically significant treatment
Oikawa et al. (2020a)	85.71%	11 recreationally active participants (5 males, 6 females) (24 ± 4 years)	60 g/day of collagen peptides (20 g post-exercise and 40 g pre-sleep)	4 × 4 min cycling at 70% of peak power output for 3 days	Deuterated water, muscle biopsy and blood samples to assess MPS TQRS and KSS to assess sleep quality	↑ in MPS with LA vs COL (p < 0.01)  ↔ in sleep quality with LA or COL
Oikawa et al. (2020b)	92.86%	22 healthy older women (69 ± 3 years)	30 g/day of collagen peptides	Resistance exercise performed twice during the 9-day study period	Saliva swab and muscle biopsy to gauge acute and long-term MPS	↑ in MPS with WP at rest and with exercise (p < 0.01, acutely and p < 0.0001, long term) ↑ MPS only with exercise in COL (p < 0.01) and no long-term effects
Average QACIS score	85%

COL Collagen peptide supplementation, Placebo, MPS Muscle protein synthesis, LA Lactalbumin, TQRS Total Quality Recovery Scale, KSS Karolinska Sleepiness scale, WP Whey protein, ↑ increased ↔ decreased