Background: 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.
Objective: 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.
Methods: 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.
Results: 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.
Conclusion: 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.