A mathematical model for seasonal variability of vitamin D due to solar radiation

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 2011-10, Vol.105 (1), p.106-112
• Main Authors: Krzyścin, J.W., Jarosławski, J., Sobolewski, P.S.
• Format: Article
• Language: English
• Subjects: blood serum; diet; Erythema; fluorescence; geophysics; Humans; mathematical models; Models, Theoretical; photobiology; photochemistry; risk; Seasonal exposure; seasonal variation; Seasons; solar radiation; Solar UV radiation; summer; Sunlight; Vitamin D; Vitamin D - analogs & derivatives; Vitamin D - blood; vitamin D deficiency; vitamin status; winter
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2011.07.008

► A model of outdoor UV exposure impact on vitamin D status in humans is developed. ► Model input is based on the irradiance observations and possible outdoor scenarios. ► Vitamin D status throughout 2010 is calculated for typical Polish indoor workers. ► The workers could not maintain adequate vitamin D level throughout most of the year. ► Boosting vitamin D level by sunbathing is risky (erythema) and not much help solution. It is widely recognized that vitamin D deficiency has detrimental health consequences. The ultraviolet (UV) B radiation increases the serum vitamin D level, expressed by 25-hydroxyvitamin-D 3 [25(OH)D]. An analytical model is presented to calculate the serum 25(OH)D changes throughout a year, caused by the solar exposure variability due to geophysical and habitual factors. The model is tuned by taking into account recent experimental results of serum 25(OH)D changes, after a series of artificial (by fluorescent tubes) UV exposures. The model uses the erythemal and vitamin D weighted irradiances, inferred from the Brewer spectrophotometer and the Kipp and Zonen broad-band meter measurements, carried out in Belsk (52°N, 21°E), Poland, in 2010. The modeled seasonal pattern of the serum 25(OH)D concentration in Polish indoor workers is only slightly different, than in subjects with typical outdoor activity habits, and in those with sun-seeking behavior. A deep minimum in the serum 25(OH)D concentration appears in late winter, regardless of outdoor activity habits. An extra sunbathing to boost the vitamin D level is not worth taking, because of a minor improvement of the vitamin D status, and because of a greater erythema risk. It would be much safer and more effective to maintain an adequate vitamin D level through diet supplements, even in summer, for non sun-seeking subjects.