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At a Glance
- What it is Collagen is the main structural protein in your skin, tendons, cartilage and bones. In aged skin, collagen fibers become fragmented1.
- Best-studied benefits Skin, knee pain during exercise and bone density, mostly in single trials of branded peptides378.
- The catch A 2025 review found no skin benefit in independently funded or high-quality trials4.
- No good evidence We didn’t find randomized trials showing collagen supplements help hair growth, gut health, heart health or weight loss.
- Top pick NAKED Collagen – the #1 pick in our guide to the best collagen powder: one ingredient, bovine collagen peptides, with the NSF Contents Certified mark.
The Short Answer: Collagen holds your skin, joints and bones together, and your body makes its own from the protein you eat. Collagen supplements may modestly help skin, nails, knee pain during exercise and bone density, but the skin benefits show up mainly in company-funded trials4, and the other benefits rest on single trials678.
On this page
Many popular claims, such as thicker hair, a healthier gut or weight loss, aren’t backed by trials we could find. If you want to try collagen, a plain collagen peptide powder is the simplest option. For the basics, see our guide to collagen peptides, and for products, our guide to the best collagen powder.
What Is Collagen and What Does It Do?
Collagen is a family of proteins that gives strength and structure to skin, tendons, ligaments, cartilage and bone. Collagen is rich in the amino acids glycine, proline and hydroxyproline; in one study, vitamin C-enriched gelatin raised blood levels of these amino acids and a marker of collagen production2. With age, collagen in the skin breaks down: aged skin shows fragmentation and loss of type I collagen fibers, which makes it more fragile1.
Collagen supplements are usually hydrolyzed collagen (collagen peptides) from cowhide, fish or pig skin. For how they’re made and absorbed, see our guide to collagen peptides.
Collagen Benefits: Claims vs Evidence
| Claim | What the research shows | Evidence |
|---|---|---|
| Smoother, more hydrated skin | Better in pooled trials; no effect in independent or high-quality trials34 | Mixed |
| Stronger nails | 42% fewer broken nails in a small study without placebo6 | Weak |
| Thicker hair | We didn’t find randomized trials | None found |
| Less joint pain | Less knee pain during sport in 139 athletes7 | Limited |
| Stronger bones | Higher bone density in 131 postmenopausal women8 | Limited |
| More muscle | More lean mass with strength training in 53 older men9 | Limited |
| Gut health (“leaky gut”) | We didn’t find randomized trials | None found |
| Heart health | We didn’t find randomized trials | None found |
| Weight loss | We didn’t find randomized trials | None found |
Skin
This is the most studied benefit. A 2021 review of 19 trials found collagen improved skin hydration, elasticity and wrinkles3. In one branded trial, 2.5 g of Verisol a day for 8 weeks reduced eye wrinkle volume by 20% in women aged 45 to 655. But a 2025 review of 23 trials found the benefits disappeared in studies without company funding and in high-quality studies, and concluded there’s no clinical evidence to support collagen for skin aging4.
Hair and Nails
In an open-label study, 25 people with brittle nails took 2.5 g of collagen peptides a day for 24 weeks; nail growth increased by 12% and broken nails fell by 42%6. Without a placebo group, it’s hard to know how much was due to collagen. We didn’t find randomized trials showing collagen supplements improve hair growth. For hair products, see our guide to biotin and collagen supplements.
Joints
In 139 athletes with knee pain during sport, 5 g of collagen peptides a day for 12 weeks reduced pain during activity more than placebo, though not pain at rest7. For joint-specific options such as UC-II, see our guide to the best collagen for joints.
Bones
In 131 postmenopausal women with low bone density, 5 g of specific collagen peptides a day for 12 months increased bone density at the spine and hip compared with placebo8. This was a single trial of a branded product.
Muscle
In 53 older men with low muscle mass, 15 g of collagen peptides after strength training for 12 weeks increased lean mass more than placebo9. Collagen lacks the essential amino acid tryptophan, so it’s an incomplete protein and shouldn’t replace other protein sources10.
Collagen Benefits for Women and Men
- Women: Most skin trials were done mainly in women35, and the bone density trial was in postmenopausal women8. See our guide to the best collagen supplements for women.
- Men: The muscle trial was in older men doing strength training9, and the knee pain trial included athletes7. See our guide to the best collagen supplements for men.
Do Collagen Supplements Work?
Sometimes, and modestly. Three things to keep in mind:
- Funding matters: In skin research, only company-funded and lower-quality studies showed benefits4.
- Branded peptides: Many positive trials used specific branded peptides at set doses, so results may not apply to every product578.
- Diet matters too: In one study, vitamin C-enriched gelatin taken before exercise doubled a marker of collagen production in 8 men2.
Who Might Benefit and Who Doesn’t Need It
Collagen may be worth trying if you’re interested in skin, nail, joint or bone support and accept that the evidence is modest. It won’t replace treatment for osteoporosis or joint disease. Collagen comes from animals, so it isn’t vegetarian; see our guide to vegan collagen for plant-based alternatives.
Our Top Collagen Pick
1 ingredientNSF Contents Certified9.5 g per serving
The #1 pick in our guide to the best collagen powder. It lists only bovine collagen peptides and carries the NSF Contents Certified mark. Most positive trials used specific branded peptides, so results may not carry over exactly to any one product.
Side Effects and Safety
Long-term safety data for collagen supplements are limited. Fish collagen isn’t suitable for people with fish allergies.
Final Verdict
Collagen is essential for skin, joints and bones, and supplements may offer modest benefits for skin, nails, knee pain during exercise and bone density3678. But the strongest skin evidence comes from industry-funded trials, and independent trials show no clear effect4. Claims about hair, gut health, heart health and weight loss aren’t supported by trials we found.
If you want to try collagen, consider NAKED Collagen, a single-ingredient bovine collagen powder with the NSF Contents Certified mark. Compare all picks in our guide to the best collagen powder.
Important: This guide is for general information and isn’t medical advice. Talk to your doctor before using collagen if you have a food allergy or take prescription medicine.
Frequently Asked Questions
What are the benefits of collagen?
What does collagen do for your body?
It gives structure and strength to skin, tendons, ligaments, cartilage and bones. In aging skin, collagen fibers break down1.
Is collagen good for you?
It’s a protein, but an incomplete one because it lacks tryptophan10, and its benefits as a supplement are modest.
What is collagen good for in women?
Do collagen supplements really work?
Does collagen help hair growth?
We didn’t find randomized trials showing it does.
Can you get collagen from food?
Yes. Your body makes its own collagen from the protein you eat, and gelatin is a food source of collagen protein2.
Sources & History
References
- Collagen Fragmentation Promotes Oxidative Stress and Elevates Matrix Metalloproteinase-1 in Fibroblasts in Aged Human Skin — American Journal of Pathology, 2009
- Vitamin C-Enriched Gelatin Supplementation Before Intermittent Activity Augments Collagen Synthesis — American Journal of Clinical Nutrition, 2017
- Effects of Hydrolyzed Collagen Supplementation on Skin Aging: A Systematic Review and Meta-Analysis — International Journal of Dermatology, 2021
- Effects of Collagen Supplements on Skin Aging: A Systematic Review and Meta-Analysis of Randomized Controlled Trials — American Journal of Medicine, 2025
- Oral Intake of Specific Bioactive Collagen Peptides Reduces Skin Wrinkles and Increases Dermal Matrix Synthesis — Skin Pharmacology and Physiology, 2014
- Oral Supplementation With Specific Bioactive Collagen Peptides Improves Nail Growth and Reduces Symptoms of Brittle Nails — Journal of Cosmetic Dermatology, 2017
- Improvement of Activity-Related Knee Joint Discomfort Following Supplementation of Specific Collagen Peptides — Applied Physiology, Nutrition, and Metabolism, 2017
- Specific Collagen Peptides Improve Bone Mineral Density and Bone Markers in Postmenopausal Women: A Randomized Controlled Study — Nutrients, 2018
- Collagen Peptide Supplementation in Combination With Resistance Training Improves Body Composition and Increases Muscle Strength in Elderly Sarcopenic Men: A Randomised Controlled Trial — British Journal of Nutrition, 2015
- Significant Amounts of Functional Collagen Peptides Can Be Incorporated in the Diet While Maintaining Indispensable Amino Acid Balance — Nutrients, 2019
Update history
- New guide covering what collagen is and does, claimed benefits graded by evidence (skin, nails, hair, joints, bones, muscle, gut, heart, weight), benefits for women and men, and whether supplements work, based on 2021 and 2025 skin meta-analyses, branded trials and studies on collagen synthesis and aging skin.
