Walk down the supplement aisle and collagen looks incredibly simple.

One tub promises healthier skin.

Another is marketed for joints.

Another contains “five types of collagen”.

Marine collagen claims one thing.

Bovine collagen claims another.

Then you discover Type I, Type II, Type III, hydrolysed collagen, collagen peptides and undenatured collagen.

So are these genuinely different products?

Yes.

But not necessarily in the way supplement marketing would have you believe.

There really are different types of collagen in the human body, and different collagen supplements can be manufactured in substantially different ways.

However, this doesn't mean that swallowing Type I collagen automatically sends it to your skin or that taking Type II delivers replacement collagen directly into your knees.

The science is considerably more interesting than that.

What Actually Is Collagen?

Collagen is the major structural protein in the human body.

Think of it less like fuel and more like part of the body's structural framework.

Collagen contributes to tissues including:

Skin

Bone

Tendons

Ligaments

Cartilage

Blood vessels

Connective tissue

There are at least 28 identified collagen types, although Types I, II and III account for much of the collagen people encounter when discussing supplements.

And these different types aren't distributed evenly throughout the body.

Type I Collagen

Type I is the most abundant collagen in the human body.

It is particularly important in:

Skin

Tendons

Ligaments

Bone

Teeth

Other connective tissues.

This is one reason Type I dominates the beauty and general collagen-peptide market.

Marine collagen is predominantly Type I, while bovine collagen commonly provides large amounts of Type I alongside Type III.

But this is our first important warning:

The fact that Type I collagen exists in your skin does not prove that eating Type I collagen specifically rebuilds your skin.

Once consumed, collagen is digested.

Some becomes individual amino acids while some small collagen-derived peptides can survive digestion and enter circulation.

Those amino acids and peptides can then participate in normal metabolism and may also influence cellular signalling.

Your digestive system isn't delivering an intact cow collagen fibre directly into your cheek.

Does Type I Collagen Actually Help Skin?

This is where things become controversial.

Several systematic reviews and meta-analyses have reported improvements in skin hydration and elasticity after oral hydrolysed collagen supplementation.

A 2023 meta-analysis involving 26 randomised trials and 1,721 participants reported improvements in hydration and elasticity. (PubMed)

A 2025 analysis of ten randomised trials involving 646 participants also reported statistically significant improvements in skin hydration and elasticity, with doses ranging from around 1–10 g daily. (PubMed)

Sounds convincing.

But keep reading.

There's a Problem With the Skin Research

A separate 2025 meta-analysis examined 23 randomised trials involving 1,474 participants.

When all studies were pooled, collagen appeared to improve:

Hydration

Elasticity

Wrinkles.

But when researchers separated the studies according to funding and quality, something important happened.

Studies without pharmaceutical-company funding found no significant benefit.

Higher-quality trials also failed to demonstrate significant improvements across the outcomes examined.

The researchers therefore concluded that there was currently insufficient clinical evidence supporting collagen supplements for preventing or treating skin ageing. (PubMed)

And a 2026 systematic review reached a similarly cautious conclusion.

Although many included trials reported improvements, most were considered at high risk of bias. (PubMed)

So CardioFire isn't going to tell you:

“Collagen definitely makes your skin younger.”

The evidence isn't strong enough for that.

A fairer conclusion is:

Hydrolysed collagen may modestly improve certain skin measurements, but the quality and independence of the evidence remains a legitimate concern.

That's considerably less exciting than the supplement adverts.

It's also considerably more useful.

Type II Collagen

Now things get more interesting.

Type II collagen is a major structural component of cartilage.

Consequently, Type II collagen supplements are commonly marketed towards:

Joint health

Knee discomfort

Osteoarthritis

Mobility.

But there's a huge distinction hiding behind the words “Type II collagen”.

Hydrolysed Type II and Undenatured Type II Are NOT the Same Thing

This is probably the most important part of this entire guide.

You'll encounter two very different products.

Hydrolysed collagen

The collagen has been broken into smaller peptides.

You generally consume it in grams.

Native or undenatured Type II collagen

The collagen's three-dimensional structure is deliberately preserved to a greater extent.

And some studies use only around:

40 milligrams per day.

Not 40 grams.

Not even 4 grams.

40 mg.

That's because undenatured Type II isn't believed to work simply by providing raw building materials.

How Could Undenatured Type II Work?

One proposed mechanism is known as oral tolerance.

Specialised immune tissue in the gut encounters tiny amounts of intact Type II collagen.

This may influence immune responses towards similar collagen found in cartilage and potentially reduce inflammatory responses.

That is fundamentally different from drinking several grams of hydrolysed collagen peptides.

A recent systematic review of undenatured Type II collagen in knee osteoarthritis found promising evidence for improvements in pain, function and range of motion, while emphasising the need for larger and longer trials. (PubMed)

A 2026 randomised placebo-controlled study also examined 40 mg/day of native Type II collagen in otherwise healthy people experiencing exercise-related joint discomfort and reported some earlier improvements in several knee-related measures compared with placebo. (PubMed)

Interesting?

Absolutely.

Proven miracle treatment for damaged knees?

No.

Does Type II Collagen Rebuild Cartilage?

Be careful with this claim.

Studies commonly assess outcomes such as:

Pain

Function

Mobility

Joint scores

Quality of life.

Those are important outcomes.

But improvement in knee pain isn't the same thing as demonstrating that somebody has regenerated a significant amount of lost cartilage.

If a supplement advert jumps from:

“Improved joint symptoms”

to

“Rebuilds cartilage”

you should immediately start asking questions.

Type III Collagen

Type III frequently occurs alongside Type I.

It contributes to the structure of tissues including:

Skin

Blood vessels

Internal organs

Connective tissues.

It is also involved in wound healing and tissue repair.

Bovine collagen products commonly contain Types I and III together.

This is why you'll frequently see:

TYPE I & III

written prominently on tubs.

But here's another marketing trap.

There is nowhere near as much convincing clinical evidence showing that specifically buying Type III collagen provides a unique Type III-specific benefit.

Its biological importance doesn't automatically establish a benefit from supplementing it.

What About Type V Collagen?

Type V collagen helps regulate the formation and organisation of collagen fibres and occurs in several tissues.

You'll sometimes see it included in products marketed as:

“5 Type Collagen”

or

“Multi Collagen”.

That sounds impressive.

But having more collagen types listed on a tub doesn't automatically make the supplement more effective.

What About Type X Collagen?

Type X is associated particularly with cartilage involved in bone development and mineralisation.

Again, that's biologically interesting.

But:

“Type X plays a role in the body”

doesn't equal:

“Taking supplemental Type X provides a clinically proven benefit.”

Those are entirely different claims.

This distinction applies throughout the supplement industry.

So What Is Hydrolysed Collagen?

You'll see several terms used:

Hydrolysed collagen

Collagen hydrolysate

Collagen peptides.

Broadly speaking, hydrolysis breaks large collagen proteins into smaller peptides.

This generally makes collagen powder easier to:

Dissolve

Digest

Mix into drinks

Incorporate into foods.

Most mainstream powdered collagen products use hydrolysed collagen.

Does Hydrolysed Mean Better?

Not automatically.

It depends what you're trying to achieve.

For a collagen-peptide supplement intended to provide collagen-derived amino acids and peptides, hydrolysis makes sense.

For undenatured Type II collagen, however, preserving the structure is central to its proposed mechanism.

So asking:

“Is hydrolysed collagen better?”

is like asking:

“Are trainers better?”

Better for what?

Marine Collagen

Marine collagen is generally derived from fish skin, scales or other fish tissues.

It is predominantly Type I collagen.

Consequently, it is heavily marketed towards:

Skin

Hair

Nails

Beauty.

But don't assume marine collagen has been proven superior for skin merely because it contains Type I.

The 2023 skin meta-analysis found source could influence some hydration results, but differences between collagen sources weren't significant for skin elasticity. (PubMed)

Marine collagen can nevertheless be useful for people who:

Eat fish but avoid beef or pork.

Prefer a marine source.

Want a Type I-rich collagen peptide.

People with fish allergies obviously need to check the source carefully.

Bovine Collagen

Bovine collagen is derived from cattle.

It commonly contains:

Type I

and

Type III collagen.

It's extremely common in powdered collagen-peptide supplements.

It can therefore be a practical general-purpose collagen source.

Again, don't get distracted by marketing claiming that Type III automatically means it will repair one specific organ.

Your body isn't a parcel sorting office for collagen powders.

Chicken Collagen

Chicken sternum/cartilage is commonly used as a source of:

Type II collagen.

This is particularly relevant to undenatured Type II supplements marketed for joint health.

Someone specifically researching joint discomfort may therefore encounter chicken-derived Type II products rather than the large tubs of bovine collagen peptides seen elsewhere.

Porcine Collagen

Collagen can also be sourced from pigs.

Like bovine sources, it contains collagen types that resemble several common human collagens.

People may avoid it for:

Dietary

Religious

Personal

or allergy-related reasons.

Check the label rather than assuming the source.

Multi-Collagen Supplements

Now we reach one of the industry's favourite selling points.

You'll see products advertising:

5 TYPES OF COLLAGEN

Types:

I

II

III

V

X.

It sounds superior to a boring product containing one or two.

But ask:

How much of each?

In what form?

What clinical dose?

What outcome are we actually trying to improve?

A 2025 randomised placebo-controlled trial investigated a combination of hydrolysed collagen and undenatured Type II collagen in people with knee osteoarthritis.

Both the collagen and placebo groups improved.

But the collagen combination wasn't significantly better than placebo for pain, function, rescue medication use or satisfaction after 12 weeks. (PubMed)

More collagen types didn't magically create a superior supplement.

Collagen for Tendons

This is particularly relevant to fitness.

Tendons are rich in collagen.

So researchers have become interested in combining collagen supplementation with resistance exercise.

A 2025 double-blind study involving recreationally active middle-aged men compared resistance training with either placebo or:

30 g hydrolysed collagen + 50 mg vitamin C

after exercise.

Both groups improved strength and muscle-related outcomes.

But the collagen group experienced larger increases in patellar tendon cross-sectional area and certain measures of tendon mechanical properties. (PubMed)

That's interesting evidence.

But notice what created the adaptation:

Collagen + progressive resistance training.

Not somebody sitting on the sofa drinking collagen powder.

Exercise Is Still Doing the Heavy Lifting

This point applies across much of fitness supplementation.

A supplement might help optimise a physiological response.

It doesn't replace the stimulus.

If you want:

Stronger muscles → resistance training matters.

Stronger bones → appropriate loading matters.

Better cardiovascular fitness → cardiovascular exercise matters.

Stronger tendons → progressive loading matters.

Collagen is not an exercise substitute.

What About Collagen for Muscle?

Collagen is protein.

But I would not choose collagen as your primary muscle-building protein.

Why?

Because collagen has an unusual amino-acid profile.

It's particularly rich in:

Glycine

Proline

Hydroxyproline.

But compared with high-quality dietary proteins, it isn't especially rich in the essential amino acids most important for stimulating muscle protein synthesis.

Collagen also lacks tryptophan.

For muscle building, foods and proteins such as:

Meat

Fish

Eggs

Dairy

Whey

Soy

and other complete proteins

generally make considerably more sense as the foundation.

Collagen may complement your diet.

It shouldn't automatically replace your normal protein intake.

What About Hair and Nails?

This is another area where marketing races ahead.

Collagen is frequently sold as:

“Hair, skin and nails.”

But hair and nails consist predominantly of keratin, not collagen.

That doesn't mean nutrition has no influence on them.

It means the simplistic argument:

“Hair needs collagen, therefore collagen supplements grow hair”

is biologically misleading.

The evidence supporting collagen specifically for hair growth is far weaker than many product labels suggest.

Does Vitamin C Matter?

Yes — biologically.

Vitamin C is required for normal collagen synthesis.

Severe vitamin C deficiency famously causes scurvy, in which collagen-related tissues are badly affected.

That is why some collagen supplements include vitamin C.

But don't jump from:

“Vitamin C is required”

to:

“Massive vitamin C doses create massive amounts of collagen.”

Once nutritional requirements are met, more isn't necessarily better.

Can Food Provide What Your Body Needs to Make Collagen?

Absolutely.

Your body manufactures collagen.

It requires amino acids and nutrients.

Foods contributing protein include:

Meat

Fish

Eggs

Dairy

Legumes

Soy

and numerous other foods.

Vitamin C-rich foods include:

Peppers

Citrus fruits

Berries

Kiwi

Broccoli

Potatoes.

You don't need a collagen tub simply because humans contain collagen.

What About Bone Broth?

Bone broth naturally contains collagen-derived gelatin and amino acids.

But the amount varies enormously depending on:

Ingredients

Bones/connective tissue used

Cooking time

Water volume

Preparation.

That makes dosing considerably less predictable than a standardised supplement.

Bone broth can be food.

It doesn't need to become medicine.

Gelatin Versus Collagen Peptides

Gelatin is essentially collagen that has undergone partial breakdown through heat.

It gels when cooled.

Hydrolysed collagen has been broken into much smaller peptides and generally dissolves more easily without forming a gel.

Nutritionally they're related.

Functionally in food they're very different.

Which Collagen Should You Choose?

Now we can make this genuinely useful.

If you're mainly interested in skin

Look at:

Hydrolysed collagen peptides

often Type I-rich.

Marine and bovine products are common.

But understand that the skin evidence remains contested, particularly when study quality and industry funding are considered. (PubMed)

If you're interested in general connective tissue or tendons

Look at research around:

Hydrolysed collagen peptides

combined with an appropriate exercise programme.

Don't buy it expecting passive tendon strengthening.

If you're specifically interested in joint discomfort

This is where:

Undenatured/native Type II collagen

becomes interesting.

Check whether the product actually says:

Undenatured

Native

UC-II

or equivalent.

Don't assume a large tub labelled “collagen peptides” is the same thing.

If you're trying to build muscle

Prioritise:

Normal dietary protein

and resistance training.

Collagen can be additional.

It wouldn't be my first-choice protein supplement for hypertrophy.

If you just want “general collagen”

A straightforward hydrolysed bovine or marine collagen peptide is simpler than paying extra purely because a product boasts five collagen types.

Don't Shop By Roman Numeral Alone

This is probably the single most useful shopping rule.

Don't think:

I = skin

II = joints

III = organs

and buy accordingly.

Instead ask:

What form is it?

Hydrolysed?

Undenatured?

What source?

Bovine?

Marine?

Chicken?

What dose?

Does it resemble the dose studied?

What outcome am I trying to achieve?

Joint symptoms?

Tendon support alongside training?

Skin?

Is there evidence for the actual formulation?

That's much harder for supplement companies to answer.

More Types Doesn't Mean Better

If two products cost:

£18 for a well-studied formulation

and

£35 for “ULTIMATE 10X MULTI COLLAGEN COMPLEX”

don't automatically assume £35 buys a better result.

You're buying a supplement.

Not collecting Pokémon.

Clinical formulation and dose matter more than the number of Roman numerals on the label.

What We Look For in CardioFire Recommended Products

Because collagen products vary so much, we're going to separate our recommendations according to what the product actually contains and what someone might reasonably be looking for, rather than declaring one collagen supplement “best for everyone”.

When assessing products, we'll look at:

The collagen source

The collagen type

Whether it is hydrolysed or undenatured

The amount supplied

How that compares with research

Other ingredients

Value for money

And whether the marketing claims go beyond the evidence.

If you'd like to see the products we've selected, head to the CardioFire Recommended Fitness Gear section.

[BUTTON: VIEW CARDIOFIRE RECOMMENDED GEAR]

I'd also put a smaller line underneath:

Some links on CardioFire may be affiliate links. If you buy through them, we may earn a commission at no extra cost to you. We choose recommendations based on usefulness, evidence and value rather than commission.

So Do Collagen Supplements Work?

There isn't a useful yes-or-no answer.

The evidence differs by:

Formulation

Outcome

Dose

Study quality

Population.

For skin, there are numerous positive trials and meta-analyses, but serious concerns remain about bias and industry funding. (PubMed)

For joints, undenatured Type II is interesting and has produced positive results in several studies, but the evidence isn't strong enough to describe it as a cartilage-restoring treatment. (PubMed)

For tendons, emerging evidence suggests collagen peptides alongside resistance training may enhance some adaptations, but the research is still developing. (PubMed)

And for muscle building, collagen shouldn't displace higher-quality complete proteins.

The Bottom Line

The TikTok version isn't completely wrong.

Different collagen supplements really can be different.

But it's not simply because:

Type I goes to your skin.

Type II goes to your knees.

Type III goes somewhere else.

What matters is the combination of:

Collagen type + source + processing + dose + intended use + evidence.

Hydrolysed collagen peptides and undenatured Type II collagen are particularly important to distinguish because they're fundamentally different preparations and are consumed at dramatically different doses.

And don't assume that a supplement containing five collagen types is automatically five times better.

The most complicated label isn't necessarily the best product.

Sometimes it's just the best marketing.