Information on Vitamin D Synthesis / Erythemal UV




  1. This website shows the times for appropriate exposure for vitamin D production and the time to reach MED (Minimal Erythema Dose) which is the standard value for producing sunburn. These times have been constructed through the newest and the most reliable scientific products. The logics of the site are based mainly on the paper "Determining an effective UV radiation exposure time for vitamin D synthesis in the skin without risk to health: Simplified estimations from UV observations" (Miyauchi and Nakajima, 2016).
  2. The recommended dietary intake of vitamin D for Japanese people older than 18 years is 5.5 µg per day. If the total daily requirement of vitamin D for Japanese people is 15 µg, the remaining ~10 µg is to be obtained from UV outdoors. The website explains the times necessary to obtain 10 µg and to reach MED.
  3. Calculations are performed for an effective exposure area of 600 cm2, which corresponds to the human face and the backs of both hands, as well as a larger area of 1200 cm2 corresponding to the shoulders and parts of the arms or legs. It is preferable to expose a larger area in order to obtain more vitamin D and lessen the demerits of UV.
  4. The results are described for people with SPT (Skin Photo Type) III. People with other than SPT III, such as SPT II or IV, are able to convert the times to reach MED and to produce 10 µg vitamin D by the correction factors shown in the Table "Skin Types".


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