Collagen for Tendons and Ligaments: What the Studies Show, Including the Vitamin C Protocol

Written by Dimitrun Irene. Updated October 30, 2026.

Collagen supplements may help tendons a little, but the evidence is small, mostly industry funded, and does not show stronger tendons or faster healing of injuries. The most promising findings are that collagen with vitamin C taken an hour before exercise raised a blood marker of collagen production in a tiny independent study, and that 5 grams a day during 14 weeks of strength training made the Achilles and patellar tendons grow slightly larger than training alone. But in those trials the tendons did not become stiffer or stronger than without collagen, a 2024 tracer study found no extra connective-tissue building in muscle with 30 grams a day, and a 2026 systematic review found collagen added no strength. For tendon pain or injury, progressive loading exercise is the treatment with the best evidence; collagen is at most a low-risk addition. This guide sets out what each study found, who paid for it, and how the vitamin C protocol is supposed to work.

Tendons connect muscle to bone and ligaments connect bone to bone. Both are made mostly of type I collagen fibres arranged in parallel bundles, which gives them their tensile strength. Tendon collagen is renewed very slowly compared with muscle protein, and blood supply to tendons is limited, which is why tendon injuries heal slowly and why the main stimulus for tendon adaptation is mechanical load. When you take collagen it is digested into amino acids and small peptides, as explained in what are collagen peptides; the question is whether supplying these building blocks at the right time adds anything to what training already does.

The idea comes from a 2017 study in the American Journal of Clinical Nutrition by Shaw, Baar and colleagues. Eight healthy men took either a placebo, 5 grams or 15 grams of gelatin, each with 48 mg of vitamin C, one hour before six minutes of rope skipping, on different days. A blood marker of collagen production (PINP) rose by 153% four hours later with 15 grams, against 54% with placebo; 5 grams made little difference. Serum taken from the men after 15 grams also increased collagen in engineered ligaments grown in the lab. The study was publicly funded. Its limits are important: it had only eight people, the blood marker mostly reflects bone rather than tendon, and it did not measure tendons themselves. A 2019 follow-up by the same group in 10 men, testing gelatin and collagen with vitamin C, found the marker rose about 20% but no treatment was statistically significant. The role of vitamin C is discussed in collagen and vitamin C.

Two German trials tested this in young men doing 14 weeks of strength training. In the first, published in 2022 with 40 men, 5 grams a day of specific collagen peptides increased the cross-sectional area of the Achilles tendon by 11.0% against 4.7% with placebo, and muscle thickness by 7.3% against 2.7%. In the second, published in 2023 with 31 men completing, the patellar tendon grew 10.7% against 6.5%, but only in part of the tendon. In both trials tendon stiffness and strength gains were the same with collagen as with placebo. A larger tendon that is not stiffer or stronger is of uncertain practical benefit. Both trials used products supplied by the manufacturer, and a co-author was the director of a collagen research institute linked to the industry.

One small study has tested it. In a 2019 Australian pilot of 20 people with long-standing Achilles tendinopathy, all doing calf strengthening, collagen was compared with placebo in a crossover design over two three-month periods. Symptom scores improved more in the first three months with collagen (12.6 points against 5.3 on the VISA-A scale) and improved further after switching. The study was investigator-led but financially supported by the collagen manufacturer, and its small size and crossover design limit conclusions. A larger trial of collagen with vitamin C before loading exercise in patellar tendinopathy is under way, co-funded by another collagen maker, with no results yet.

In a 2018 trial in 50 athletes with chronic ankle instability, 5 grams a day of collagen peptides for six months with home exercises improved a self-reported ankle stability score more than placebo (5.3 points against 0.7), and the collagen group reported fewer re-injuries during follow-up, although measured ankle stiffness did not differ and the groups started with different scores. Part of the cost was paid by the manufacturer. In a 2019 study of 24 men given 20 grams a day around a bout of 150 drop jumps, jump performance recovered slightly better at 48 hours (90% against 79% of baseline), with no difference in soreness or in collagen blood markers; that study was funded by a collagen producer whose employees were co-authors. Collagen's wider evidence for joints is in collagen for joints and exercise.

A 2024 trial in Medicine and Science in Sports and Exercise, from researchers in Bochum and Maastricht, gave 25 men either 30 grams of collagen a day (two 15-gram doses) or a placebo during a week of intense training, and measured how fast new connective tissue and muscle protein were built using a stable isotope tracer. The rates were the same: 1.97% a day with collagen and 2.00% with placebo for connective tissue in muscle, and 1.34% in both groups for muscle protein. The study did not measure tendon directly, but it is one of the few direct measurements of tissue building rather than a blood marker or a size change, and it found nothing extra from collagen. It had no external funding, although some authors have received industry grants in the past.

Studies of tendon size used 5 grams a day of specific collagen peptides alongside strength training. The pre-exercise studies used 15 grams of gelatin or collagen with about 48 to 50 mg of vitamin C, taken about an hour before a short bout of loading. The 2026 review's authors suggested 15 to 30 grams with at least 50 mg of vitamin C before heavy training, but that is their interpretation of a small and mixed evidence base. Gelatin and collagen peptides provide the same amino acids; peptides dissolve more easily, including in hot drinks, as discussed in collagen in coffee. General guidance on taking collagen is in how to take collagen peptides, and amounts beyond those studied are discussed in can you take too many collagen peptides.

Progressive loading is the foundation of tendon rehabilitation: exercises that load the tendon gradually and consistently over weeks to months, such as heavy slow resistance or eccentric exercises, guided by a physiotherapist or sports medicine doctor. Rest alone tends to weaken tendons further, and complete ruptures, such as a torn Achilles or ACL, need medical assessment and often surgery or bracing. Adequate total protein supports recovery generally; collagen is an incomplete protein, so whey or other complete proteins are better for muscle, as explained in collagen peptides vs protein powder. Collagen may be a reasonable addition to a loading programme, not a replacement for it.

Collagen supplements have a small, mostly industry-funded evidence base for tendons. Taken during strength training they may make tendons slightly larger, and small trials report better symptom scores in tendinopathy and ankle instability, but no study has shown stronger tendons, faster healing of injuries or extra strength, and the one independent tracer study found no added tissue building. If you want to try it, 5 grams a day, or 15 grams with vitamin C before loading, matches what was studied; give it at least three months, as discussed in how long collagen takes to work, and keep the loading programme at the centre. What to look for in a product is in how to choose collagen peptides, and collagen's uses for active men in collagen benefits for men.

This article summarizes published research for general information. Tendon and ligament injuries should be assessed by a doctor or physiotherapist.