Collagen supplements have become enormously popular in recent years. Walk through any health food shop and you’ll find powders, capsules, and drinks all promising younger skin, healthier joints, and stronger bones. The global collagen market is projected to reach billions of dollars, driven largely by anti-ageing claims.

But does the science support the marketing? I’ve reviewed the clinical evidence, and the picture is more nuanced than supplement companies suggest. Some benefits have reasonable research support. Others remain speculative. Let me walk you through what we actually know.

What is collagen?

Collagen is the most abundant protein in your body. The word comes from the Greek “kólla,” meaning glue, which gives you a sense of its function. It’s the structural scaffolding that holds your tissues together, comprising about one-third of your total protein content and three-quarters of your skin’s dry weight 1.

There are at least 16 different types of collagen in the human body, though types I, II, and III account for 80-90% of the total. Type I is found primarily in skin, tendons, and bones. Type II is the main component of cartilage. Type III appears alongside type I in skin and blood vessels.

Your body produces collagen naturally, using amino acids from protein in your diet along with vitamin C, zinc, and copper as cofactors. Production peaks in your 20s and then gradually declines, roughly 1% per year after age 30. Sun exposure, smoking, excessive sugar intake, and poor sleep can accelerate this decline.

Does oral collagen actually get absorbed?

This is the question that matters most, and it’s been debated for decades. The traditional view was that collagen, being a protein, would simply be broken down into individual amino acids during digestion, just like the protein in a steak. Those amino acids would then be distributed throughout the body according to the body’s needs, not necessarily redirected to your skin or joints.

However, more recent research has challenged this simplistic view. Studies have shown that hydrolysed collagen (collagen that’s been broken down into smaller peptides) can be absorbed intact in the form of di- and tripeptides 2. These collagen-specific peptides, particularly those containing hydroxyproline, have been detected in the bloodstream after oral supplementation.

The bioavailability of hydrolysed collagen appears to be reasonably good, with studies suggesting absorption rates around 90%. Once absorbed, some evidence suggests these peptides may stimulate fibroblasts (the cells that produce collagen) to increase collagen synthesis. Whether this translates into meaningful clinical benefits is what the trials attempt to answer.

My honest take: the absorption argument isn’t as simple as “it just gets digested.” There’s legitimate evidence that collagen peptides can reach target tissues. The more important question is whether they do anything useful once they get there.

What are the proven benefits of collagen?

1. May slow skin ageing

This is the primary reason most people take collagen, and it’s also where the strongest evidence exists.

A systematic review and meta-analysis of 19 randomised, double-blind, placebo-controlled trials involving 1,125 participants found that hydrolysed collagen supplementation improved skin hydration, elasticity, and wrinkle appearance compared to placebo 3. The improvements were statistically significant, though the actual magnitude of benefit was modest.

Another meta-analysis of 26 trials came to similar conclusions, noting improvements in skin hydration after 8 weeks and in elasticity and wrinkle depth after 12 weeks of supplementation 4. The typical dose in these studies ranged from 2.5g to 10g daily.

What this means in practice: you might notice somewhat plumper, more hydrated skin after a few months of supplementation. Will collagen supplements make you look twenty years younger? No. Will they slow the inevitable march of ageing to some degree? Possibly. The effects are real but not dramatic.

The NHS notes that while some studies show promise, more research is needed to understand long-term effects and optimal dosing 5.

2. May help with burn wound healing

Severe burns represent a significant clinical challenge. The skin, which normally provides a protective barrier, is compromised, leading to fluid loss, infection risk, and prolonged healing times.

A randomised, double-blind trial of 31 men with 20-30% surface area burns found that oral hydrolysed collagen supplementation improved serum prealbumin levels (a marker of nutritional status), wound healing rate, and reduced hospital stay compared to placebo 6.

The proposed mechanism is that collagen provides the amino acid building blocks needed for tissue repair during the hypermetabolic state that follows severe burns. Glycine and proline, two amino acids abundant in collagen, are particularly important for wound healing.

This is a small study, and burn treatment involves many other factors beyond nutrition. But for patients recovering from significant burns, collagen supplementation may be a reasonable adjunct to standard care.

3. May benefit bone density

Bone isn’t just mineral. About 30% of bone mass is organic material, predominantly type I collagen, which provides the flexible framework upon which calcium and phosphorus crystals are deposited.

Animal studies have shown that collagen peptide supplementation can increase bone mass and stimulate bone formation 7. Human studies are more limited but generally supportive.

A 12-month randomised controlled trial of postmenopausal women found that daily collagen peptide supplementation (5g) increased bone mineral density at the spine and femoral neck compared to placebo 8. The increases were modest (around 3-7%), but in a population at high risk for osteoporosis, any improvement is potentially meaningful.

Whether collagen supplementation can actually prevent fractures remains unknown. That would require much larger, longer trials. But as a complement to calcium and vitamin D supplementation, collagen might have a role in bone health strategies.

4. May reduce cellulite appearance

Cellulite affects approximately 85% of women over age 20. It occurs when fat tissue pushes through the connective tissue beneath the skin, creating a dimpled appearance, most commonly on the thighs, buttocks, and abdomen.

A double-blind controlled study of 105 women with moderate cellulite found that six months of collagen peptide supplementation reduced cellulite severity and improved skin waviness, dermal density, and the appearance of the subcutaneous border compared to placebo 9.

The effect was more pronounced in women with normal body weight compared to those who were overweight, suggesting that collagen works by strengthening the connective tissue matrix rather than by reducing fat.

This is one of the few cellulite treatments with any scientific support, though I’d temper expectations. The improvements were measurable but not transformative.

5. May support muscle mass in older adults

Sarcopenia, the age-related loss of muscle mass and strength, begins as early as age 40 and accelerates after 65. By age 80, many people have lost 30-50% of their skeletal muscle, contributing to falls, fractures, loss of independence, and increased mortality.

A 12-week double-blind controlled study of 53 elderly men with sarcopenia found that collagen peptide supplementation combined with resistance training led to greater increases in muscle strength and fat-free mass, and greater decreases in fat mass, compared to resistance training with placebo 10.

The mechanism may relate to collagen’s high content of glycine and arginine, which are involved in creatine synthesis and may support muscle protein synthesis during exercise.

Note that collagen alone, without exercise, probably won’t do much for muscle. The synergy with resistance training appears to be important.

6. May ease osteoarthritis symptoms

Osteoarthritis is characterised by the breakdown of cartilage in joints, leading to pain, stiffness, and reduced mobility. Since cartilage is primarily composed of type II collagen, there’s biological plausibility for collagen supplementation.

A 13-week double-blind controlled study of 30 patients with knee osteoarthritis found that collagen peptides (from either pig skin or bovine bone) improved overall osteoarthritis symptoms and quality of life compared to baseline 11.

The mechanism may involve collagen peptides stimulating chondrocytes (cartilage cells) to increase proteoglycan synthesis, essentially encouraging the body’s own cartilage repair processes.

If you’re considering supplements for joint health, collagen and glucosamine work through different mechanisms and might be complementary. Neither will reverse established arthritis, but both may provide some symptomatic relief.

7. May benefit certain autoimmune skin conditions

This is a more speculative area. Diffuse cutaneous systemic sclerosis is a rare autoimmune disease characterised by skin thickening and internal organ involvement.

A double-blind controlled study found that oral type I collagen didn’t significantly improve overall skin scores in scleroderma patients. However, in a subgroup analysis of patients with late-stage disease, there was a significant improvement in skin thickness scores 12.

The evidence here is weak and the condition is rare. I mention it mainly for completeness, as it’s sometimes cited in collagen research summaries.

Side effects of collagen

Collagen supplements are generally well tolerated. The most commonly reported side effects are mild and relate to the digestive system:

Mild diarrhoea
Stomach heaviness or bloating
Heartburn
Rash (uncommon)
Persistent aftertaste
Fatigue (rare)

According to the Mayo Clinic, collagen supplements are considered generally safe for most people, though they recommend consulting a healthcare provider if you have food allergies or are taking medications 13.

Safety precautions (2 key contraindications)

1. Pregnancy and breastfeeding: There’s insufficient safety data on collagen supplementation during pregnancy or lactation. Most experts recommend avoiding supplements unless specifically advised by your healthcare provider. The same applies to people with significant liver or kidney dysfunction, as protein metabolism may be altered in these conditions.

2. Food allergies: Collagen supplements are typically derived from bovine (cow), porcine (pig), marine (fish), or poultry sources. If you have allergies to any of these foods, you could react to the corresponding collagen supplement. Marine collagen, in particular, comes from fish and shellfish and should be avoided by anyone with seafood allergies.

For those with egg allergies, be aware that some collagen products contain eggshell membrane as an additional ingredient.

When’s the best time to take collagen?

Most research doesn’t specify timing, suggesting it doesn’t matter much. That said, some practitioners recommend taking collagen on an empty stomach (first thing in the morning or before bed) to maximise absorption without competition from other proteins.

If you experience digestive discomfort, taking collagen with food may help. The trade-off might be slightly reduced absorption, but it’s better than not taking it at all.

Consistency matters more than timing. Most studies showing benefits used daily supplementation for at least 8-12 weeks. If you’re going to try collagen, give it a fair trial of two to three months before deciding whether it’s working for you.

What helps your body make collagen?

If you’d prefer to support collagen production naturally rather than supplementing directly, focus on these nutrients:

Vitamin C: Essential cofactor for collagen synthesis. Deficiency (scurvy) leads to collagen breakdown.
Proline and glycine: Amino acids abundant in collagen. Found in bone broth, gelatin, chicken skin, pork skin.
Arginine: Supports collagen synthesis. Found in nuts, seeds, meat, dairy.
Copper and zinc: Trace minerals involved in collagen cross-linking. Found in shellfish, nuts, seeds, whole grains.

Lifestyle factors also matter. Smoking, excessive sun exposure, high sugar intake, and chronic stress all accelerate collagen breakdown. Addressing these may be as important as any supplement.

Different types of collagen supplements

You’ll encounter several forms:

Hydrolysed collagen (collagen peptides): Pre-digested for better absorption. Most commonly used in research.
Gelatin: Partially hydrolysed collagen. Gels when mixed with liquid. Less convenient but cheaper.
Undenatured type II collagen: A different approach that works through immune modulation rather than providing building blocks. Used specifically for joint health.
Collagen-boosting supplements: Contain vitamin C and amino acid precursors rather than collagen itself.

For skin and general benefits, hydrolysed collagen peptides from any source (bovine, marine, porcine) appear to be effective. For joint-specific benefits, some evidence supports type II collagen specifically.

What this means for you

Collagen supplements aren’t snake oil, but they’re also not miracle workers. The evidence for skin hydration and elasticity is reasonably solid. The evidence for joint, bone, and muscle benefits is promising but less robust.

If you’re considering collagen, here’s my practical advice:

Try hydrolysed collagen peptides at 5-10g daily for at least 12 weeks
Take it consistently, timing doesn’t matter much
Don’t expect dramatic changes, subtle improvements are more realistic
Ensure adequate vitamin C intake to support collagen synthesis
Continue proven strategies like sun protection, exercise, and adequate protein intake
If you see no benefit after three months, it may not be worth continuing

For those with specific conditions like osteoarthritis or osteoporosis, collagen might be one component of a broader treatment strategy that includes appropriate medical care, not a replacement for it.

Benefits and side effects of glucosamine - another popular joint supplement
Benefits and side effects of vitamin C - essential for collagen production
Health foods beneficial for osteoarthritis
Benefits and side effects of hyaluronic acid - often combined with collagen for skin health

References

Lodish H, et al. Molecular Cell Biology. 4th edition. Section 22.3, Collagen: The Fibrous Proteins of the Matrix. https://www.ncbi.nlm.nih.gov/books/NBK21582/
León-López A, et al. Hydrolyzed Collagen—Sources and Applications. Molecules. 2019;24(22):4031. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835901/
de Miranda RB, et al. Effects of hydrolyzed collagen supplementation on skin aging: a systematic review and meta-analysis. Int J Dermatol. 2021;60(12):1449-1461. https://pubmed.ncbi.nlm.nih.gov/33742704/
Wang H, et al. A systematic review and meta-analysis of collagen supplements in skin aging. Int J Food Sci Nutr. 2023;74(3):395-408. https://pubmed.ncbi.nlm.nih.gov/36652192/
NHS. How to get more fibre into your diet. https://www.nhs.uk/live-well/eat-well/digestive-health/how-to-get-more-fibre-into-your-diet/
Sinha A, et al. Effect of hydrolyzed collagen on wound healing rate in thermal burn patients. Complement Ther Clin Pract. 2020;38:101066. https://pubmed.ncbi.nlm.nih.gov/31859087/
Guillerminet F, et al. Hydrolyzed collagen improves bone metabolism and biomechanical parameters in ovariectomized mice. Bone. 2010;46(3):827-834. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3750261/
König D, et al. Specific Collagen Peptides Improve Bone Mineral Density and Bone Markers in Postmenopausal Women—A Randomized Controlled Study. Nutrients. 2018;10(1):97. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793325/
Schunck M, et al. Dietary Supplementation with Specific Collagen Peptides Has a Body Mass Index-Dependent Beneficial Effect on Cellulite Morphology. J Med Food. 2015;18(12):1340-1348. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4685482/
Zdzieblik D, et al. Collagen peptide supplementation in combination with resistance training improves body composition and increases muscle strength in elderly sarcopenic men. Br J Nutr. 2015;114(8):1237-1245. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4594048/
Schauss AG, et al. Effect of the novel low molecular weight hydrolyzed chicken sternal cartilage extract, BioCell Collagen, on improving osteoarthritis-related symptoms. J Agric Food Chem. 2012;60(16):4096-4101. https://www.ncbi.nlm.nih.gov/pubmed/24852756
Postlethwaite AE, et al. A multicenter, randomized, double-blind, placebo-controlled trial of oral type I collagen treatment in patients with diffuse cutaneous systemic sclerosis. Arthritis Rheum. 2008;58(6):1810-1822. https://www.ncbi.nlm.nih.gov/pubmed/18512816
Mayo Clinic. What is collagen, and why do people use it? https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/collagen-supplements/faq-20457882