New Guidelines on Sunlight Exposure for Vitamin D

The researchers explained that before health experts can create new sunlight guidelines from these findings, further calculations are necessary.

“The revision of the guidelines will take more work,” said Professor Young, “This is done by “weighting” a given solar UVR spectrum with biological function, each of which has its own wavelength dependence.”

“To give an example of this: max UVB content (at solar noon) of solar UVR is about 5%, but this 5% will cause about 85% of the sunburn because the UVB is much more effective than the 95% of UVA at causing sunburn. The amount of UVB in the sun depends on the height of the sun. So these calculations shift minute by minute,” he added.

“Risk-benefit calculations need to be done with sunburn and vitamin D with our new spectrum,” he added. “This will tell us the safest time to be out in the sun at any time of day, season, or latitude. The good news is that vitamin D is produced at a much lower UVR dose than [what] causes sunburn. Many people deliberately seek sun exposure to get a tan.”

To conclude, the researchers say that sunlight guidelines according to blood serum vitamin D levels could include more refined assessments of the risks and benefits of sun exposure when compared to those based on pre-vitamin D levels.

The team also states that limitations to their study include a wide range of times in which volunteers had exposure to radiation. They also mentioned that there was a lot of interpersonal variation, although they expected this in vitamin D studies.

“What these authors have done is to expose humans to ultraviolet radiation that contained multiple wavelengths and measured blood levels of 25-hydroxyvitamin D, ” Michael F. Holick, M.D., Ph.D., and Professor of Medicine, who was not involved in this research yet authored the research behind the current sunlight guidelines, told MNT, “They did not measure pre-vitamin D3 in the skin.”

In future work, the researchers say that they will conduct risk-benefit calculations and model the effect of melatonin on different skin types.