The effect of monthly mean global horizontal solar radiation and sunshine duration on vitamin d levels in young women

Abstract

Aim: The most important reason for vitamin D deficiency is the lack of synthesis in the skin. The synthesis of vitamin D can be affected by many variables such as geographical region, race, season, monthly average daily sun exposure (MADSD), monthly average daily global horizontal solar radiation (MADGHSR). In this study, we aimed to investigate possible association between vitamin D levels and MADSD and MADGHSR in young women. Methods: This is a retrospective study evaluating the levels of Vitamin D classified by age, seasons, months, MADGHSR and MADSD in women aged between 15-45 years admitted to a secondary state hospital. Results: All of the women involved were at reproductive age and approximately 94.6% of them had vitamin D levels below 30 ng/mL. The median (minimum-maximum) vitamin D level was 16.1 (3.6-49.4) ng/mL in summer and 14.3 (3.2-49.8) ng/mL in winter (p=0.001). The rate of vitamin D deficiency (<20 ng/mL) was 68.1% in summer and 75.1% in winter (p<0.001). The median MADGHSR was 4.6 (3.4-5.7) hours in winter and 6.9 (5.2-7.2) hours in summer and the median MADSD was 3.3 (1.6-3.5) watt/m²/day in winter and 15.2 (12.2-15.8) watt/m²/day in summer. Vitamin D level was weakly correlated with age (r=0.082, p=0.002), MADSD (r=0.075, p=0.001) and MADGHSR (r=0.062, p=0.006). Conclusion: We found that MADGHSR and MADSD had an effect on vitamin D synthesis in addition to factors related with personal and environmental situations. We suggest that routine optimal dose vitamin D replacement is necessary in geographies similar to the population in our study.