Optimal Duration of Sun Exposure for Adequate Cutaneous Synthesis of Vitamin D in Indian Cities: An Estimate Using Satellite-Based Ultraviolet Index Data

Little Flower Augustine¹, K Madhavan Nair² and Bharati Kulkarni*³

Received: June 18, 2018;   Published: June 27, 2018

DOI: 10.26717/BJSTR.2018.06.001313

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Abstract

Lack of region specific guidelines on sun exposure for acquiring optimal vitamin D could be a bottle neck for developing effective education strategies for Indian population. We calculated the required sun exposure time for each day for one year considering 10 % exposure, type V skin accounting for 1000 IU of vitamin D per day for clear and cloudy sky conditions. The UV Index provided by TEMIS satellite for 10 Indian stations ranging in latitude from 8 degree to 38 degrees for 1 year were obtained, and were converted to the vitamin D effective UV radiation, applied minimal erythemal doses and Holicks rule. Attenuation of UV radiation due to clouds was accounted for by using data on daily clouds measured in octas from Agricultural meteorology database. The seasonal variations were also accounted for. Our data showed a latitude-dependent change in sun exposure time. A seasonal variation was also observed. After accounting for clouds, an exposure of 30-35 minutes appeared to be sufficient in all stations except for Srinagar. Seasonal variations were high in stations ranging from 14 minutes to 133 minutes. About 75 % of the days were conducive for sun exposure in the stations studied. The estimated sun exposure time, if validated, can be a useful tool for behavioural change communication facilitating safe sun exposure for satisfying vitamin D status in tropical countries like India.

Keywords: Vitamin D from Sun Exposure; India; Estimated Duration of Exposure

Abstract| Introduction| Materials and Methods| Results| Discussion| Limitations| Conclusion| Acknowledgement| References|