Collagen

Collagen supplementation · Collagen Peptides · Hydrolyzed Collagen · Collagen Hydrolysate

Snapshot

Indications	Contraindications
Knee osteoarthritis symptoms^{1, 2} Skin hydration and elasticity³ Menopausal hair loss⁴ Fat-free mass with training⁵ Tendon morphology with training⁵ Post-exercise energy intake⁶ Nail health⁷	Fish allergy⁸ Egg allergy⁸

Collagen is the main structural protein of skin, tendon, cartilage, and bone; supplements supply hydrolyzed peptides that, once absorbed, stimulate fibroblast activity and matrix synthesis⁷. Production declines with aging⁷. Supplementation is used for skin elasticity, nails, hair, and joint pain⁷, with appetite and metabolic effects an early-stage use.

In osteoarthritis, meta-analyses of randomized trials found oral collagen improved pain and function^{1, 2}. Skin evidence is split: one meta-analysis found better hydration and elasticity, while a 2025 meta-analysis found no effect in non-industry-funded or high-quality trials. In physically active women, a 2025 randomized crossover study found collagen peptides raised glucagon-like peptide-1 and insulin and lowered energy intake at a later meal⁶. Products list collagen as powders, liquids, capsules, and tablets from marine, bovine, or porcine sources; see Form comparison.

The main caution is the source material: product labels in the United States warn of fish, egg, or milk content⁸. A 2024 case report traced an athlete's adverse analytical finding for a prohibited substance to a contaminated collagen powder⁹.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

70 sources, 56 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources