Collagen

Collagen is the most abundant protein in the human body, accounting for roughly a third of total protein mass. It acts as the primary structural scaffold for skin, bones, tendons, cartilage, and connective tissue — giving these tissues their strength, elasticity, and integrity.

The body produces collagen naturally, but production declines gradually from the mid-twenties onwards and accelerates with age, UV exposure, smoking, and poor nutrition.

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What does collagen do?

Collagen's roles vary depending on which tissue it supports:

• Skin — maintains elasticity, firmness, and hydration
• Bones — forms the organic matrix onto which calcium and phosphate mineralise, contributing to bone strength and density
• Joints and cartilage — cushions joints, supports mobility, and resists compression
• Tendons and ligaments — provides tensile strength and flexibility
• Muscles — supports connective tissue surrounding muscle fibres

There are at least 28 known types of collagen. Types I, II, and III are the most relevant to general health: Type I is found in skin, bones, and tendons; Type II in cartilage; Type III in skin and blood vessels.

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Dietary sources

The body synthesises collagen from amino acids — primarily glycine, proline, and hydroxyproline — alongside key micronutrients. Eating a varied diet that supplies these building blocks is the most reliable way to support natural collagen production.

Foods that directly provide collagen include bone broth, chicken (particularly skin and cartilage), fish, and pork skin. These contain pre-formed collagen that the body can use after digestion.

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Collagen supplements

Collagen supplements — most commonly sold as hydrolysed collagen peptides or collagen hydrolysate — are collagen that has been broken down into smaller fragments (peptides) for easier absorption. They are typically derived from bovine, porcine, marine (fish), or chicken sources.

Clinical research has examined supplementation across several areas:

• Skin — Multiple randomised controlled trials report improvements in hydration and elasticity; however, a 2025 meta-analysis in The American Journal of Medicine found these benefits disappeared when only studies without industry funding were analysed
• Joints — Aggregate evidence from 35 RCTs supports small-to-moderate reductions in joint pain, particularly for osteoarthritis; effect sizes are modest
• Bone density — The most robust evidence comes from post-menopausal women; a 12-month RCT found specific collagen peptides alongside calcium and vitamin D attenuated bone mineral density loss
• Muscle — Evidence is limited and conflicting; collagen is low in leucine and is not considered equivalent to whey or other complete proteins for muscle protein synthesis

Most positive collagen trials have been funded by supplement manufacturers. Independent research is limited, and effect sizes where benefits are found tend to be modest. Supplements are best viewed as a potential complement to an adequate diet, not a substitute for one.

When considering a supplement, hydrolysed collagen peptides are the most bioavailable form. Look for products with third-party testing certification to reduce contamination risk, and ensure adequate vitamin C intake alongside supplementation, as it is required for collagen synthesis.

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Natural ways to support collagen production

Beyond diet, several lifestyle factors influence collagen levels:

• Minimise excess sun exposure — UV radiation degrades collagen and accelerates skin ageing
• Avoid smoking — smoking impairs collagen synthesis and damages existing collagen fibres
• Stay well hydrated — adequate fluid intake supports tissue health and skin elasticity
• Prioritise sleep and recovery — collagen synthesis is upregulated during sleep
• Limit excess sugar — advanced glycation end-products (AGEs) formed from high sugar intake cross-link and stiffen collagen fibres

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Key takeaways

• Collagen is the body's primary structural protein, essential for skin, bone, joint, and connective tissue health
• Natural production declines with age; diet, lifestyle, and targeted supplementation can help support levels
• A varied diet rich in protein, vitamin C, zinc, and copper provides the building blocks for collagen synthesis
• Supplement evidence is promising in some areas — particularly bone density and joint pain — but is limited by small trials and pervasive industry funding
• Hydrolysed collagen peptides are the most bioavailable supplement form; pair with vitamin C for best effect

For personalised advice on nutrition and supplementation, consult a registered dietitian or your GP.

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Related terms

• Collagen peptides — Collagen broken into small fragments through hydrolysis for easier absorption; the most common supplement form
• Hydrolysed collagen — Another term for collagen peptides; collagen that has been partially broken down by water and enzymes
• Glycine — The most abundant amino acid in collagen, also found widely in dietary protein sources
• Vitamin C — An essential cofactor for collagen synthesis; deficiency impairs collagen production
• Bone mineral density (BMD) — A measure of the mineral content of bones, used to assess fracture risk