Vitamin C

What the evidence says

A 2023 systematic review found only seven eligible randomized publications with 139 volunteers. Treated skin appeared smoother and less wrinkled and showed objective lightening of pigmentation, while hydration improved equally at vitamin C and placebo sites.^[1]

One six-month double-blind vehicle-controlled study of 5% vitamin C reported improvement in global photodamage, skin microrelief, deep furrows, and microscopic elastic-tissue measures. The result supports biological activity for that formulation, not every vitamin C serum.^[3]

A pooled analysis of 31 small randomized vehicle-controlled studies involving 741 healthy volunteers found less ultraviolet-induced pigmentation with topical vitamin C. The trials were generally short and the analysis was industry affiliated.^[4]

A separate wrinkle review found seven eligible studies, but every included treatment combined vitamin C with another ingredient or procedure. That makes it difficult to attribute the reported changes to vitamin C alone.^[2]

Formulation chemistry is unusually important. L-ascorbic acid is unstable and oxidizes with light, air, and heat, while many more-stable derivatives have less in-vivo efficacy evidence. No concentration, derivative, vehicle, package, or regimen has emerged as universally best.^[5][6]