Sun-induced production of vitamin D3 throughout 1 year in tropical and subtropical regions: relationship with latitude, cloudiness, UV-B exposure and solar zenith angle

This study evaluated the differences in vitamin D3 synthesis two different latitudes throughout 1 year using an vitro model, which simulates cutaneous D photoproduction. Borosilicate ampoules containing 7-dehydrocholesterol (7-DHC) were exposed to sunlight hourly daylight hours, day per month for a year, Fortaleza (latitude 03° 43′ 01" S—LAT3° S) and Sao Paulo 23° 32′ 53" S—LAT23° S). Later, photoisomers of 7-DHC (tachysterol lumisterol) measured by high-performance liquid chromatography system (HPLC). Vitamin weighted UV radiation (UVBVitD) solar zenith angle (SZA) calculated during same periods both latitudes. occurred locations, as expected lower than 35°. Median photoconversion through was higher LAT3°S [median (IQR): LAT 3°S 4.1% (6.0); 23°S 2.9% (4.5); p value = 0.020]. production strongly correlated with UV-B (LAT3° S, r 0.917; < 0.0001 at LAT23° 0.879; 0.0001) SZA − 0.924; LAT23°S, 0.808; 0.0001). starts later especially winter. Lowest percentages observed June cities, although, compared LAT3° S conversion over 50% winter period. Cloudiness impaired photoproduction even summer months Our results provide data help guide medical recommendations sensible sun exposure promote latitudes, seasonality, time cloudiness status Brazil.