Collagen
The main structural protein in skin, tendon and bone — and a popular supplement.
Collagen is the most abundant structural protein in the body, giving skin, tendons, ligaments and bone their tensile strength. Supplemental collagen is hydrolysed into peptides so it can be absorbed.
It matters because the supplement's reputation runs ahead of a genuinely mixed evidence base: eaten collagen is digested into amino acids like any other protein rather than being delivered intact to your face, and the more interesting trials concern tendon, joint and skin outcomes with modest, inconsistent effects.
In practice, total protein intake and resistance training do more for connective tissue than a branded collagen powder; for skin specifically, the evidence for sun protection and retinoids is far stronger.
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Written and reviewed by Mathew Beale, MSc Biotechnology, University of Reading.
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