Effects of oral vitamin E and [beta]-carotene supplementation on ultraviolet radiation-induced oxidative stress in human skin

Background: Ultraviolet radiation (UVR) generates reactive oxygen species in skin that can play a role in skin damage, but reports about the photoprotective properties of oral antioxidant supplements are conflicting. Objective: We examined the ability of 2 lipid-soluble antioxidants, vitamin E and [beta]-carotene, to reduce markers of oxidative stress and erythema in human skin exposed to UVR. Design: Sixteen healthy subjects took either [alpha]-tocopherol (n = 8; 400 IU/d) or [beta]-carotene (n = 8; 15 mg/d) for 8 wk. Biopsy samples before and after supplementation were taken from unexposed skin and skin 6 h after 120 mJ/[cm.sup.2] UVR. The effects of supplements on markers of oxidative stress in skin and the minimal erythema dose to UVR were assessed. Results: Supplementary vitamin E was bioavailable, the plasma concentration increased from 14.0 [+ or -] 0.66 ([bar.x] [+ or -] SEM) to 18.2 [+ or -] 0.64 [micro]g/mL (P < 0.01), and the skin concentration increased from 0.55 [+ or -] 0.09 to 1.6 [+ or -] 0.19 ng/mg protein (P < 0.01). Supplementary [beta]-carotene increased plasma concentrations from 1 [+ or -] 0.3 to 2.25 [+ or -] 0.3 [micro]g/mL (P < 0.05), but skin concentrations were undetectable. Before vitamin E supplementation, UVR increased the skin malondialdehyde concentration from 0.42 [+ or -] 0.07 to 1.24 [+ or -] 0.16 nmol/mg protein (P < 0.01), whereas oxidized or total glutathione increased from 9.98 [+ or -] 0.4% to 12.0 [+ or -] 1.0% (P < 0.05). Vitamin E supplementation significantly decreased the skin malondialdehyde concentration, but neither vitamin E nor [beta]-carotene significantly influenced other measures of oxidation in basal or UVR-exposed skin. Conclusions: Vitamin E or [beta]-carotene supplementation had no effect on skin sensitivity to UVR. Although vitamin E supplements significantly reduced the skin malondialdehyde concentration, neither supplement affected other measures of UVR-induced oxidative stress in human skin, which suggested no photoprotection of supplementation. KEY WORDS Lipid-soluble vitamins, oxidative stress, skin, photoprotection, human study