Gelatin or collagen before tendon loading raises a blood marker of collagen synthesis in a small trial, but evidence that it improves tendons or prevents injury is limited and inconsistent
Interpretation
The protocol rests on Shaw et al. 2017: 8 healthy men, 15 g vitamin C-enriched gelatin before skipping doubled PINP over 3 days, with no tendon or injury outcomes. Small trials report faster Achilles tendinopathy improvement (20 adults, industry-funded pilot) and greater patellar tendon stiffness (17 young female footballers), but a 2024 meta-analysis of 19 RCTs (768 adults, 613 M) found no effect on tendon mechanical properties and only very-low-certainty, non-robust evidence for tendon size, and a 45-athlete trial found no rise in muscle connective protein synthesis with 30 g collagen. No trial measured tendon injuries or compared timings.
Practical implication
Treat collagen or gelatin as an optional add-on to a structured tendon-loading programme, not a treatment. If used, trials mostly used 15 g a day for 8-12 weeks or longer. Check allergies and kidney health first and choose batch-tested products. Evidence is mostly in men and not in triathletes.
Sources
7 sources, independently verified.
5 g or 15 g vitamin C-enriched gelatin or placebo 1 h before 6 minutes of rope skipping, three times a day for 3 days. Collagen amino acids in blood peaked about 1 h after intake; 15 g doubled the collagen-synthesis marker PINP; serum taken after gelatin increased collagen content and mechanics of lab-engineered ligaments. No tendon, pain or injury outcomes; men only; PINP is a whole-body marker.
Collagen peptides showed the clearest benefit for joint function and joint pain; collagen synthesis rose with 15 g/day; no significant muscle protein synthesis advantage over higher-quality protein. Authors call for larger samples, more women and elite athletes, and direct measures such as biopsies and MRI.
Mostly 15 g/day for about 12 weeks with training. Tendon cross-sectional area: 4 studies, 114 participants, SMD 0.67, very low certainty and not robust to excluding one study. Tendon mechanical properties: 4 studies, 111 participants, SMD 0.05, no effect, very low certainty. No effect on soreness after muscle damage. Suggests ~15 g/day for at least 8 weeks may be reasonable while stressing limited evidence.
After resistance exercise, 30 g collagen raised plasma glycine and proline more than 30 g whey, but neither increased muscle connective protein synthesis over 5 h versus placebo (0.068 and 0.072 vs 0.058 %/h, P = 0.09); only whey raised myofibrillar protein synthesis. Measures muscle connective tissue, not tendon, over hours.
Pilot double-blind placebo-controlled crossover: 2.5 g specific collagen peptides twice daily plus daily calf strengthening and return-to-running. VISA-A improved +12.6 with collagen vs +5.3 with placebo in the first 3 months; 6-month totals similar in both orders. Underpowered; funded by the product manufacturer.
30 g collagen hydrolysate (vs energy-matched placebo) after each session for 10 weeks, with 500 mg vitamin C in both groups. Patellar tendon stiffness rose 18.0% vs 5.1% and Young's modulus 17.3% vs 4.8%; tendon size, muscle thickness and strength unchanged. Small, young female footballers, no injury outcomes.
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