The effect of vitamin D added to sunscreen on plasma vitamin D metabolites in rats

Vitamin D, most of which is synthesized in the skin under the influence of sunlight, can be obtained from natural foods in trace amounts. Vitamin D deficiency has become a global health problem due to factors that limit the use of sunlight. Current approaches for vitamin D supplementation are limited to oral intakes. In this experimental study, the effects of sunscreen cream with added vitamin D on serum vitamin D metabolites were investigated. In the study 8-weeks-old Wistar Albino male rats were used. Eight animals (Group B) were sacrificed to determine the initial values of biochemical parameters. Remaining 32 animals were randomly divided into 4 groups. T group with only dorsal shaving; TD group in which only vitamin D3 was applied to the shaved area; TG group, in which only sunscreen cream was applied to the shaved area; TDG group, in which sunscreen cream with added vitamin D3 was applied to the shaved area. After 8 weeks of applications, serum 25(OH)D2, 25(OH)D3 and 24,25(OH)2D3 levels were determined. Skin samples taken from the shaved areas were examined histopathologically. Serum 25(OH)D2 values of all animals were found at trace levels and were not included in the evaluation. The mean serum 25(OH)D3 values of the B, T, TD, TG, and TDG groups were 17.66±5.70; 13.49±3.06; 54.06±13.03; 19.60±2.70; 67.21±16.49 ng/mL respectively. In terms of serum 25(OH)D3 values, a statistically significant difference was detected between the T group and the TD group (p<0.001), and between the TG and TDG groups (p=0.002). A positive correlation was found between serum 25(OH)D3 and 24,25(OH)2D3 parameters (r=0.772; p<0.001). No statistically significant difference was observed between the groups in terms of histopathology (vascular proliferation, sabeseous gland hyperplasia, inflammatory response and epithelial thickness). In conclusion, vitamin D added to sunscreen increased serum vitamin D levels by showing transdermal activity.