Collagen: What the Science Actually Says (From Someone Who’s Been Taking It for Years)

I've been taking collagen supplements for years now. Powders stirred into my morning coffee, the odd course of capsules, and a liquid shot when I fancied a change.

Do I know, hand on heart, that it's "working"? No.

But here's the thing that keeps me buying it: the times I've stopped taking collagen, I've noticed it. My skin seems to feel thinner and drier, my nails don't grow as quickly and tend to break more easily, and my hair seems to lose some of its fullness and look thinner.

Now, correlation isn't proof. There could be plenty of other reasons for those changes, particularly as I've got older. But it's enough personal evidence to keep me going back to collagen — and enough uncertainty to make me want to look properly at what the science actually says before recommending it to anyone else.

What the science says and why collagen matters as we age

The first time I started using collagen, it was because I'd heard about its supposed anti-ageing benefits. My main concern, like many women, was fine lines and wrinkles.

The theory sounded simple: collagen helps support the structure of our skin, so if we're losing collagen as we age, surely supplementing it should help replace some of that loss?

Unfortunately, biology isn't quite that straightforward.

Collagen is a structural protein found throughout the body, including our skin, bones, tendons and cartilage. It accounts for roughly a quarter to a third of the protein in the human body.

Our collagen production and the amount of collagen in our skin change as we age, but for women there's another important factor: oestrogen.

The decline in oestrogen around menopause is associated with a significant reduction in skin collagen, thickness, hydration and elasticity. Some research suggests that as much as 30% of dermal collagen may be lost during the first five years after menopause.

Suddenly, you can see why collagen has become such a hot topic for women over 40.

Walk into almost any health-food shop or pharmacy and you'll find shelves of collagen supplements. Two of the most common are marine collagen, usually derived from fish, and bovine collagen, derived from cattle.

You'll also increasingly see products labelled "vegan collagen", although that's slightly misleading. Plants don't naturally produce collagen. Most vegan collagen products are actually collagen builders containing ingredients such as amino acids, vitamin C and minerals intended to support your body's own collagen production. It's an interesting area of research, but it's not the same thing as taking animal-derived collagen peptides.

Marine or bovine collagen — is one actually better?

This is where the beauty industry's marketing gets interesting.

Marine collagen is frequently promoted for skin, hair and nails, while bovine collagen is often marketed more towards joints, bones and muscles.

But how true is that?

Marine collagen is predominantly Type I collagen, the main collagen type found in skin. Bovine collagen generally provides Types I and III, both of which are also present in skin and connective tissues.

That gives manufacturers a plausible reason to market marine collagen towards beauty. But it doesn't mean marine collagen somehow knows to head straight for your face while bovine collagen takes a detour towards your knees.

Once we look at actual human studies, the distinction becomes much less convincing.

Research comparing different collagen sources hasn't established that marine collagen is clearly superior for skin, nor that bovine collagen should be reserved for joints and muscles. Studies of hydrolysed fish, bovine and porcine collagen have also found collagen-derived amino acids and small peptides appearing in the bloodstream after consumption.

So, for me, the more important question isn't simply marine or bovine?

It's what form is it in, what dose are you getting, and has the actual product been properly studied?

The absorption argument — both sides

This is where it gets genuinely contested, and where I think a lot of marketing oversimplifies things.

The sceptical case

Collagen is a large protein, and your digestive system can't simply absorb a whole collagen molecule and deliver it to your face.

During digestion, collagen is broken down into amino acids and smaller peptides. Critics therefore argue that swallowing collagen doesn't mean you're directly "replacing" the collagen in your skin. Your body ultimately decides what to do with those nutrients.

And this is where the research gets uncomfortable for the supplement industry.

While a number of trials and previous reviews have reported improvements in skin hydration and elasticity from collagen supplementation, a major 2025 systematic review and meta-analysis found something rather interesting.

When all the studies were pooled together, collagen appeared to improve hydration, elasticity and wrinkles. But when researchers looked specifically at studies that weren't funded by pharmaceutical or supplement companies, those benefits disappeared. Higher-quality studies also failed to show significant benefits.

That's a pretty important caveat when you're standing in a shop considering spending £30 or £40 on another tub of powder.

The counter-argument

There is, however, another side.

Hydrolysed collagen has already been broken down during manufacturing into much smaller collagen peptides.

Human studies show that after we consume hydrolysed collagen, not everything necessarily ends up as individual amino acids. Small hydroxyproline-containing peptides can appear in the bloodstream.

The interesting theory is that some of these peptides may do more than simply provide raw materials. Laboratory and clinical research suggests they may act as biological signals involved in processes such as fibroblast activity and the production of components of the skin's extracellular matrix.

In other words, the argument isn't really that the collagen in your coffee travels directly to the wrinkle beside your eye and fills it in.

If collagen supplements do work, the mechanism is potentially far more subtle: providing amino acids and bioactive peptides that may influence the body's own processes.

And several systematic reviews and clinical trials have reported modest improvements in things such as skin hydration and elasticity after taking hydrolysed collagen for a number of weeks.

So who's right?

At the moment, possibly a bit of both.

There is enough evidence to make oral collagen genuinely interesting, but not enough high-quality, independent research to justify some of the extraordinary claims you'll find on supplement packaging.

Powder, capsule or liquid — does the format matter?

This is probably less about magic and more about dose and practicality.

Powder is my usual choice because it's relatively easy to get several grams of hydrolysed collagen in one serving. I can stir it into my coffee and forget about it.

Capsules are convenient, particularly for travelling, but check the label carefully. A capsule can't physically hold the same quantity as a large scoop of powder, so you may need several capsules to reach the amount used in some clinical studies.

Liquid collagen can also be convenient, but I haven't found convincing evidence that simply being liquid makes collagen inherently more effective. What matters more is the type of collagen peptides, the amount you're actually consuming and the overall formulation.

So rather than being seduced by whether something comes in a glamorous little bottle, I'd turn it around and read the back.

How many grams of collagen am I actually getting?

And is it hydrolysed collagen or collagen peptides?

Those questions probably tell me considerably more than the packaging on the front.

So, do I think collagen works?

I'm not going to pretend I have a laboratory report proving that collagen has turned back my biological clock.

I haven't.

What I have is years of taking it and repeatedly noticing changes when I stop — particularly in my nails, hair and skin.

That's personal experience, not scientific proof, and there's an important difference between the two.

What surprised me when I looked properly at the research was that the scientific answer isn't a simple yes or no either.

There are controlled trials and reviews reporting improvements in skin hydration and elasticity. There is evidence that small collagen-derived peptides can reach the bloodstream after hydrolysed collagen is consumed.

But there are also legitimate concerns about study quality, small sample sizes and industry funding. One of the strongest recent reviews found that the apparent skin benefits weren't reproduced when only higher-quality or independently funded studies were considered.

For me, that puts collagen in the category of promising rather than proven.

And perhaps that's where the beauty industry sometimes gets ahead of itself.

Marine collagen isn't a magic beauty powder programmed to find your wrinkles. Bovine collagen isn't exclusively destined for your joints. And a £50 liquid shot isn't automatically better than a scoop of hydrolysed collagen powder simply because it comes in prettier packaging.

Will I continue taking collagen?

Yes.

Not because I believe it's performing miracles, but because I've used it for years, I notice a difference when I stop, and there's enough science behind it to make me think there may be something worthwhile happening.

But I'll also keep doing the less glamorous things that we already know matter to ageing skin: eating enough protein, getting vitamin C through my diet, protecting my skin from the sun, using evidence-based skincare and looking after my health generally.

Because if there's one thing I've learnt while researching anti-ageing, it's this:

there is rarely one miracle ingredient — no matter how beautiful the tub it comes in.