A variety of studies have shown beneficial effects of different types of phototherapy in skin disorders. Such therapy leads to enhanced cutaneous vitamin D synthesis, which may be one of the mechanisms of action. Furthermore, another nutrient, folate, can probably also be influenced by UV radiation. The aim of our study was to investigate the influence of low-dose narrowband UVB (nUVB) phototherapy of patients with psoriasis, atopic eczema and other skin disorders on serum levels of 25(OH) vitamin D (the serum marker for vitamin D status) and on serum and erythrocyte-folate. 25(OH) vitamin D (25(OH)D), serum and erythrocyte-folate levels were measured before and after low-dose nUVB (TL-01 tubes) phototherapy of these patients. The spectrum of the TL-01 tube was compared with the solar spectrum, and the efficiency spectra of vitamin D photosynthesis were calculated. For patients with a high initial 25(OH)D serum level (> 80 nmol/l), no significant (P = 0.36) increase in 25(OH)D levels was seen, in contrast to patients with a low initial level (< 80 nmol/l) where a significant increase (P < 0.001) was observed. The increase was 30-60%, depending on the UVB dose (2.35-13.4 J/cm(2)). No significant nUVB-effect was found on the erythrocyte and serum-folate level. Low-dose nUVB treatment gives a significant increase (P < 0.001) of the vitamin D status in persons with low initial levels of 25(OH)D, but no effect on the folate level.
