Hyaluronic Acid
A water-binding molecule of the skin and joint matrix. Taken orally there's moderate evidence for improved skin hydration — but the established medical uses are injection and topical application.
How it works
Hyaluronic acid is a molecule the body makes that binds large amounts of water, keeping skin, joint cartilage and eyes moist and elastic. Applied topically it plumps the skin; taken orally there are signals of improved skin hydration and joint comfort. The body's own content declines with age.
Dosage
Orally typically 120–240 mg/day. Important: oral, topical, and injected are three different applications with different evidence.
Considerations
For oral hyaluronic acid there are some small RCTs on skin hydration and fine lines. For knee osteoarthritis, oral is mixed — the established route there is injection (medical). Overall promising, but the evidence for ingestion is still thin.
