Training
Collagen and tendon
Tendon and ligament injuries are the ones that end seasons and there has never been much to offer nutritionally, which is exactly the vacuum a thin literature gets marketed into.
What most people believe
Collagen supplements rebuild joints and tendons. It is the same protein, so eating it puts it where it is needed.
What the evidence actually says
The objection everyone raises, and why it is not quite decisive
Eaten collagen is digested into amino acids like any other protein. It does not travel to a tendon as collagen, and the idea that it does is nonsense. That objection is correct as far as it goes.
Where it stops short: collagen is unusually rich in glycine and proline, which are exactly the amino acids tendon needs in quantity, and some collagen-derived peptides do appear in blood intact. So there is a plausible mechanism that is not "the collagen goes to the tendon" — it is closer to supplying an unusual raw material mix at a moment the tissue can use it.
Plausible is not proven, and the table marks it contested for that reason.
What the actual trials look like
Small. Often short. Frequently funded by companies selling the product, which is not disqualifying and is worth knowing. Several show improvements in tendon or ligament stiffness and in joint pain; others show nothing.
The most-discussed protocol combines a dose of gelatin or collagen with vitamin C, taken shortly before loading the tissue, on the reasoning that a brief rise in circulating amino acids coinciding with mechanical load is what the tendon can act on. It is an elegant hypothesis with genuinely limited human outcome data behind it.
This is what an early literature looks like. It is not fraud and it is not established science, and the honest thing is to say which one it is rather than to round it to whichever suits.
The part that is not contested
Vitamin C is required to build collagen at all. The enzymes that stabilise the collagen triple helix cannot work without it — that is what scurvy is, connective tissue failing for want of a cofactor.
Which means anyone genuinely low in vitamin C has a real connective tissue problem, and it is cheap to rule out. Beyond sufficiency, more vitamin C does not build more collagen, for the same reason more of any cofactor does not.
What actually strengthens a tendon
Load. Progressive, patient, boring load. Tendon adapts far more slowly than muscle — months rather than weeks — which is precisely why people get hurt: the muscle is ready to do more well before the tendon is.
Nothing in this category substitutes for that, and the risk of a supplement here is not the money. It is believing you have addressed a problem you have not, and adding load on that belief.
The numbers, and how firmly they are held
| What it describes | Figure | Evidence |
|---|---|---|
| Dose used in the trials Gelatin or hydrolysed collagen | 15 g | Contested |
| Timing before loading the tissue The mechanism the protocol assumes | 30–60 min before loading | Contested |
| Vitamin C required for collagen synthesis This part is not in doubt | 50 mg | Established |
Two of these are marked contested deliberately. The trials are small, short and often industry-funded, and rounding that up to established would be exactly what this site exists not to do.
Established means the position stands agree and you can act on it. Probable means the weight of evidence points one way with real dissent. Contested means it is genuinely unsettled, and anyone selling you certainty about it is selling something.
What follows is easier when you know what you are already eating.
What to actually do
Load it properly first
Progressive loading is the intervention with actual evidence. Tendon adapts over months, and the gap between muscle readiness and tendon readiness is where injuries live.
Rule out low vitamin C, then stop worrying about it
It is genuinely required for collagen synthesis. Beyond sufficiency, more does not build more.
If you try it, know what you are buying
A plausible mechanism with early data. That can be worth a punt on your own money; it is not worth adding load in the belief that the tissue is protected.
Sources
- Gelatin supplementation and collagen synthesis — a controlled trial
- NIH Office of Dietary Supplements — Vitamin C
This page is education, not medical advice. It does not diagnose anything and it is not a substitute for a clinician who knows your history. Sports nutrition in particular is a field where the evidence moves, and where a figure that suits a trained twenty-five-year-old may be wrong for you.
Every nutrient named above, measured — in the app.