Tendons are collagen-infused super-strong bridges that connect muscles to bones helping you to move your limbs. When overused, overloaded or damaged, these same tendons can cause us a lot of pain and movement impairment. Aside from medical treatments and physiotherapy rehabilitation programs that help tendon injuries heal, there has been growing interest in how specialised tendon-targeted nutritional supplements can aid repair and recovery. And for good reason, hydrolysed collagen is a key component of many of these supplements. In this blog post, I look at where the evidence stands for nutritional supplements helping with tendon healing.
This blog post is all about tendons. So what are they? Tendons are strong rope-like bands of connective tissue that attach muscle to bone. That makes tendons essential in helping limbs move as they provide the bridge linking the force generated by the muscle to the bone. Tendons also help reduce the risk of muscle injury by absorbing some of the impact force your muscles experience when you run or jump.
Tendons are made up mostly of collagen. You’ll also find elastin in tendons which, as its name suggests, is a protein that gives tissues some degree of stretch and recoil ability.
Tendons do a lot of work. And in cases of overuse and injury, this can cause pain, swelling and reduced performance. There are two common conditions affecting the health of tendons. The first is inflammation which is called tendonitis. The other condition, called tendinosis, is more associated with the breakdown of the collagen fibres that make up most of the tendon. Collectively, these conditions come under an umbrella term called tendinopathy.
Overuse is a common cause of tendinopathy. This is where the tendon is repeatedly strained until tiny tears form. The shoulder, wrist, knee, shin and heel are the common places you’ll see tendinopathies.
Sports people are at high risk of developing tendinopathy. As one example, in runners, some estimates put the incidence of tendinopathy at 10 percent developing it each year. In athletes, common locations for tendinopathy include the Achilles and patellar knee cap. Tendinopathy is also common in people over the age of 40, in those who do repetitive tasks, and in people with poor muscle strength.
Now this website has its focus on nutrition as that’s my expert area. So I’m going to leave well alone the medical and physiotherapy management of tendinopathies – you can do your own reading on this area and seek out appropriate professional advice. And because the symptoms of tendinopathy can be similar to other conditions such as arthritis, it is important to seek medical advice when faced with joint pain that doesn’t resolve after a week or two of rest.
Treating tendon injuries with nutrition
With tendinopathy such a common problem, there has been a lot of interest in the potential benefit that dietary interventions and nutritional supplements could play in treating it. Especially when used together with medical and physiotherapy treatment.
Right on cue, we have a recently published review paper that collated the research field of nutritional supplements for treating tendinopathies. It explored what interventions have been tried and what were the outcomes.
Let’s get into what the review looked at. In all, 16 studies (12 of which were randomised controlled trials) were identified. The studies looked at a range of nutritional supplements in the clinical management of tendinopathy. The tendinopathies were located in the Achilles, rotator cuff, patellar and plantar heel.
I’ll go over in a bit of detail the nutritional supplements used so you can appreciate the common themes.
There were two studies that used a commercial supplement called Tendoactive®. In it, you’ll find mucopolysaccharides, type I collagen and vitamin C. Mucopolysaccharides are long chains of sugar molecules found throughout the body that provide structural support and lubrication and also regulate cell growth.
Three studies used the commercial supplement Tendisulfur®. This supplement contains mucopolysaccharides, hydrolysed collagen, arginine, lysine, vitamin C, bromelain (which is an enzyme found in pineapples and linked with reducing inflammation) along with chondroitin, glucosamine, the herb Boswellia and myrrh of the biblical “Three wise men” fame.
Two studies used the commercial supplement Tenosan® which contains arginine, alpha-ketoglutarate, hydrolysed type I collagen, mucopolysaccharides, vitamin C, bromelain and ViNitrox® which contains a mixture of plant polyphenols.
Collagen peptides alone were featured in two studies. The remaining studies used omega-3 fatty acids, turmeric, hydroxymethylbutyrate (HMB), and vitamin C either in isolation or combined with gelatin (which is simply undeatured collagen). And finally, one study used creatine.
That’s a real mixed bag, but the clear common ingredient was collagen. More about collagen shortly.
What did the review find?
Most of the studies found positive clinical outcomes. Improvements in pain, function and tendon structure could all be seen following nutritional supplementation.
When nutritional supplements were combined with other treatments, it appeared the benefit was magnified. Common treatments included eccentric training (which corresponds to the downward lowering phase of weight lifting) or extracorporeal shockwave therapy (known as EWST) where high-frequency shock waves are given to an injured tendon to stimulate healing.
Many of the supplements I’ve just outlined have anti-inflammatory properties. That means they could be capable of downregulating inflammatory pathways in tendinopathy. So, this could explain some of the pain benefits. Reduced pain is definitely a great outcome for a person, but there could be other effects going on related to collagen synthesis and tendon repair. This is the biggest area of interest, but one that the review was less clear on giving direction on.
The review was not without limitations. It included a range of study designs so there was a lot of variability between the studies. So, treat the findings with some level of caution.
While nutritional supplements may seem safe and have fewer side effects compared to pain medications, they still carry risks. This is especially true for high-performing athletes who undergo drug testing for banned substances and where there can be a risk of supplement contamination. For anyone considering trialling supplements for tendon repair and recovery, it is important to be educated about their use and what exactly you are taking.
Collagen for your joints
But back to collagen as that was the common ingredient across the supplements studied in the review. Collagen makes up about three-quarters of the dry weight of tendons. That’s a lot of collagen. The crosslinking strength of collagen helps the tendon to withstand high-impact stresses and shear forces.
The research base for using oral hydrolysed collagen for a range of health benefits has been growing. Taking a more exercise recovery and joint injury perspective, a review paper from 2021 looked at the role of collagen supplementation. And the findings, albeit based on a small research field, were positive for collagen. It suggested that collagen at doses of 5 to 15 grams per day is beneficial in improving joint functionality and reducing joint pain. This benefit was enhanced when complemented with a rehabilitation exercise protocol.
A reason why collagen supplements may reduce joint pain is that they increase collagen levels in the cartilage. Together with also increasing the production of proteoglycan (an important structural protein in connective tissue) and elastin – thereby reducing tissue damage and decreasing pain. It is also thought that collagen peptides may display some level of anti-inflammatory effect, further decreasing pain and inflammation.
Collagen and skin health
It is easy to dismiss most of what I’ve covered in this post as it is true: the evidence base is still small. Among the common criticisms you hear about collagen, many dismiss it out of hand for having no evidence for a benefit and with no plausible reason why it should have any effect different to any other protein source you eat. Oh, and all that research is funded by ‘Big Collagen’ don’t you know? All three claims are completely….wrong.
The most researched area to do with oral collagen supplements is to do with skin health. We now have dozens of double-blinded randomised controlled trials showing a benefit on skin hydration, skin elasticity and wrinkles. I went into a deep dive into this area in a previous blog post so you can get the full details here.
In that blog post, I outlined the positive findings of a systematic review from 2021 of 19 clinical trials that looked at collagen supplements and skin health. But research never stands still and there has been yet more research since then. So much so, that only in the last few months, a new systematic review has been published.
This new review could analyse 26 randomised controlled trials of oral collagen supplements that looked at skin hydration and skin elasticity. And just like the 2021 review, a significant benefit was seen with almost every study pointing in the right direction for a benefit.
No, all the research is not funded by the collagen industry
But isn’t all the research funded by the collagen industry? No. Of those 26 studies on skin health I just mentioned, 11 had no funding from the collagen industry nor did any of the research team report a conflict of interest. And these ‘untainted’ trials were just as likely to show a benefit as those with industry links. Playing the ‘industry funding’ card is a lazy form of critical analysis.
Sure, you can always find fault with any individual study. But for anyone to claim that there is ‘no evidence collagen supplements work’ is living in scientific denial. If anything, I am more sceptical of people who dismiss collagen out of hand. That was a valid position 10 years ago with a limited research base. But not today. And especially when faced with growing evidence across many different areas where it seems collagen supplements offer a benefit for many conditions.
How collagen works
Those dismissive claims that collagen is no different to any other protein you eat so can’t have a unique biological effect are just so far off the mark. There is a plausible and well-understood mechanism where collagen can have direct effects on collagen production in the body different to any other protein source.
That’s because when you eat collagen, it is digested and absorbed into the bloodstream where both single amino acids and unique dipeptides and tripeptides appear. These small peptides have a unique fingerprint because of the presence of the amino acid hydroxyproline. What’s special about hydroxyproline? It is unique to collagen and is made from the amino acid proline with the help of vitamin C. So these small peptide fragments only exist in the blood from internal collagen breakdown or from the collagen we eat.
Absorbed collagen peptides not only redistribute to the skin but can act as signalling molecules, binding to receptors on the surface of fibroblasts. Fibroblasts are skin cells that are major producers of collagen. This receptor binding stimulates fibroblasts to produce collagen, elastin (needed for skin elasticity) and hyaluronic acid (for water retention). This is a key point as it provides a plausible mechanism by which collagen consumption can directly affect our skin. And similar types of pathways exist in cells that produce collagen found in cartilage and tendons.
What it all means
There is a plausible use case for why collagen-containing nutritional supplements could support tendon injury repair and recovery. The rationale for why collagen may work with tendon repair has a solid support base coming from the benefit of hydrolysed collagen supplements on skin health along with joint conditions such as osteoarthritis. All from something that is naturally part of foods and has little evidence of any adverse problems.