As a nutritionist, one thing I regularly say about supplements is: if it sounds almost too good to be true, then it probably is.

Firstly, collagen is a protein, just like you get in meat, milk or beans, but it’s particularly important in animals because it makes up a lot of our connective tissue: the tissue that helps hold our bodies together. 

It’s the most abundant protein in the human body, with potentially up to 30% of our body’s protein being collagen, with lots in our tendons, ligaments, bones and skin.

Importantly, your body can make collagen without eating collagen. That’s why people who never eat animal products don’t just fall apart. As long as they eat enough protein, vitamin C and other nutrients, we don’t need to eat collagen to make our own.

Even if you take collagen, it doesn’t travel right into your skin or joints. Like other proteins, it gets digested into amino acids and smaller peptides. Some of those peptides might have specific effects, but the idea that collagen powder gets turned right into skin collagen is not how digestion works.

How is collagen made?

So where do we get collagen? Well, that’s the really fantastic part, especially if you sell it. 

Collagen is made from by-products of the meat, poultry and fish industries. 

In simple terms, you take collagen-rich parts, bones, connective tissue, cartilage, skin and even fish scales, process them and extract the collagen. 

If you’ve ever made stock from bones and noticed it turns jelly-like when it cools, that’s gelatin, which forms from collagen when it breaks down. 

A bit of an oversimplification, but you get the idea.

Then you turn it into a powder and sell it as it is, or in a formula with other added ingredients. 

Add a brand name, slick packaging and a good marketing story, and a relatively unglamorous by-product can become a premium wellness product.

None of that processing is a bad thing, by the way. Whey protein, one of the highest quality proteins on the market, was also originally a by-product of cheese-making. 

Collagen marketing

The issue isn’t processing though, it’s what claims are made once it goes to market.

Today, the collagen industry is doing very well. Between 2017 and 2025, the market value of collagen peptides doubled from US$720 million to US$1,453 million. 

Not bad for a by-product.

So what is collagen actually supposed to do? 

Well, depending on who’s selling it, almost everything. 

It’s marketed for smoother skin, fewer wrinkles, stronger hair and nails, healthier joints, better bones, improved tendons, faster recovery, muscle growth and even “calming” the nervous system.

In nutrition science, the problem with being marketed as a panacea is that every specific claim needs evidence behind it. 

The question is not simply “does collagen work?” but “what does it work for, in which people, at what dose, and compared with what?” 

Collagen research

Recently, an umbrella review was used online to support the vague claim that “collagen works”. Its summary looked positive: favourable results for skin, muscle and osteoarthritis. 

But when we look more closely, the authors rated 15 of the 16 included reviews as low or critically low quality. 

Many underlying studies were small, short, used different types of collagen, combined collagen with other ingredients, or compared collagen with weak control groups.

That last point matters. If collagen is compared with nothing, or with a non-protein placebo, we can’t always tell whether any benefit is specific to collagen, or simply due to extra protein, the other ingredients in the formula or even a placebo effect. 

A collagen product beating a poor comparator is not the same as proving collagen has special properties.

It’s worth pointing out too that there are different types of collagen, so we can’t say that if one type has a benefit, all collagen will have the same effect. 

Don’t even get me started on the formulations where collagen is combined with other trendy supplements, and the actual dose of collagen can be pretty meagre.

I’m not saying collagen doesn’t work. There’s some very interesting research on osteoarthritis-related joint pain, skin hydration, and possibly tendon support when combined with proper rehabilitation. 

But “may help in some contexts” is very different from “this supplement fixes skin, joints, gut health, recovery and ageing”.

Saying so is not evidence-based… and if collagen was a new drug on the market, people wouldn’t accept the poor level of evidence we have right now. The evidence is interesting, but not strong enough to justify the certainty of some people promoting collagen.

Undeserved credibility

And that’s a major problem because collagen is no longer just sold by supplement companies. It’s promoted by influencers, beauty brands, wellness clinics, pharmacies and even some people with medical credentials, which gives the marketing an extra layer of undeserved credibility.

This is where collagen’s marketing becomes so powerful. It’s not just selling protein; it’s selling reassurance. Crippled with arthritis? Try collagen. Worried about wrinkles? Here’s collagen. Struggling with gut issues? Have you heard of collagen? 

It’s also marketed heavily at women of a certain age, who are already being told from every direction that ageing is a problem to be managed, slowed or fixed.

Also, once we’ve spent money on something premium, we’re inclined to believe it’s working. That doesn’t mean people are lying. Expectation, hope and placebo effects can shape how we feel… and some people may be getting genuine benefits too.

But if someone starts collagen while also improving their diet, exercising more, sleeping better or taking other supplements (which is pretty common), it becomes very hard to know which of those caused the improvement.

And that’s where I think collagen’s most realistic use might be: an “everything and the kitchen sink” approach. 

If you’re trying to throw every possible solution at a problem, like joint pain or skin health, and you don’t mind spending the money, you could always try some collagen too. The worst that could happen is your wallet gets lighter.

Just remember this, if you hear someone saying, with absolute confidence, that collagen is the greatest thing since sliced bread and it’ll solve all your health issues, turn and run the other way — especially if they happen to be selling it too.

• Richie Kirwan has a PhD in clinical nutrition, is a registered nutritionist (RNutr) with the AfN, a researcher of nutrition and heart disease, and a senior lecturer in nutrition and exercise physiology at Liverpool John Moores University. He comes from Co Waterford. For more of his work, see his Instagram page