Dietary fish-oil supplementation in humans reduces UVB-erythemal sensitivity but increases epidermal lipid peroxidation

Abstract

Ultraviolet radiation (UVR)- induced erythema may be mediated in part by free radical-generated tissue damage, including lipid peroxidation. We have examined the effect of dietary fish oil rich in ω-3 fatty acids upon susceptibility to UVB-induced erythema and epidermal lipid peroxidation. Fifteen volunteers took 10 g fish oil, containing 18% eicosapentasnoic acid and 12% docosahexaenoic acid, daily for 3 or 6 months. Sensitivity to UVB was assessed at intervals on fish oil, and 2.5 months after stopping treatment. Paired skin shave biopsies were taken from six subjects, at baseline and 3 months, from both irradiated and control skin. Fatty acid composition was analyzed and thiobarbituric acid-reactive substances measured as an index of lipid peroxidation. With increasing time on fish oil the minimal erythema dose rose progressively, from 18.9 ± 13.9 mJ/cm2 (mean ± SD) at baseline to 41.1 ± 16.6 mJ/cm2 at 6 months, p < 0.01. Ten weeks after stopping fish oil the minimal erythema dose fell to 23.1 ± 4.9 mJ/cm2, p < 0.05. Epidermal total ω-3 fatty acids rose from 1.8 ± 0.4% total fatty acids (mean ± SEM) to 24.2 ± 3.9% at 3 months, p < 0.01. This was accompanied by a rise in thiobarbituric acid-reactive substances in irradiated skin from 6 ± 0.3 (mean ± SEM) to 18.5 ± 2.6 A532/g skin, p < 0.01. Hence dietary ω-3 fatty acids produce a pronounced reduction in UVB-erythemal sensitivity, although susceptibility of skin to lipid peroxidation is increased. Thus, ω-3 fatty acids may act as an oxidizable buffer, protecting more vital structures from free radical damage. © 1994.