Determining an Effective UV Radiation Exposure Time for Vitamin D Synthesis in the Skin Without Risk to Health: Simplified Estimations from UV Observations

UV radiation contains erythemally weighted UV, as well as UV that synthesizes vitamin D-3. Here, we attempted to determine the relationship between these factors by numerical simulation of atmospheric parameters, such as total ozone, using a simplified SMART2 model for radiative transfer. Both forms of UV were almost linearly correlated with each other for a comparably large UV radiation exposure, larger than UV Index similar to 1.6. If erythemally weighted UV, which carries a risk of sunburn, is known, the amount of UV exposure needed for vitamin D synthesis in the epidermis can be estimated using this relationship. The production of 10g (400IU) of vitamin D per day takes approximately 1/3 of the time needed to reach the minimal erythemal dose (MED) for an effective skin area of 600cm(2) for skin phototype III. For an area of 1200cm(2), 1/6 of that exposure time suffices. From a UV Index that is commonly used, the risks and benefits can be evaluated using this linear relationship, which will enable people to effectively manage their UV exposure and consider the risks and benefits to optimize health outcomes.