DIETARY FISH-OIL SUPPLEMENTATION IN HUMANS REDUCES UVB-ERYTHEMAL SENSITIVITY BUT INCREASES EPIDERMAL LIPID-PEROXIDATION

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 omega-3 fatt y acids upon susceptibility to UVB-induced erythema and epidermal lipi d peroxidation. Fifteen volunteers took 10 g fish oil, containing 18% eicosapentaenoic acid and 12% docosahexaenoic acid, daily for 3 or 6 m onths. Sensitivity to UVB was assessed at intervals on fish oil, and 2 .5 months after stopping treatment. Paired skin shave biopsies were ta ken from six subjects, at baseline and 3 months, from both irradiated and control skin. Fatty acid composition was analyzed and thiobarbitur ic acid-reactive substances measured as an index of lipid peroxidation . With increasing time on fish oil the minimal erythema dose rose prog ressively, from 18.9 +/- 13.9 mJ/cm(2) (mean +/- SD) at baseline to 41 .1 +/- 16.6 mJ/cm(2) at 6 months, p < 0.01. Ten weeks after stopping f ish oil the minimal erythema dose fell to 23.1 +/- 4.9 mJ/cm(2), p < 0 .05. Epidermal total omega-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. Thi s was accompanied by a rise in thiobarbituric acid-reactive substances in irradiated skin from 6 +/- 0.3 (mean +/- SEM) to 18.5 +/- 2.6 A(53 2)/g skin, p < 0.01. Hence dietary omega-3 fatty acids produce a prono unced reduction in UVB-erythemal sensitivity, although susceptibility of skin to lipid peroxidation is increased. Thus, omega-3 fatty acids may act as an oxidizable buffer, protecting more vital structures from free radical damage.