>With UV, that mechanism is the production of vitamin D in the body, a lack of which causes a wide variety of health issues and may have a link to the developme

>With UV, that mechanism is the production of vitamin D in the body, a lack of which causes a wide variety of health issues and may have a link to the development of cancer. I imagine that vitamin D production and DNA damage are separate events. Presumably, both can occur at the same time. So would someone who took vitamin D supplements but didn't get sun exposure be slightly less likely to develop cancer than someone who got just enough sunlight for their body to produce enough vitamin D? If that's the case, it's not really a general rule that small exposures to carcinogens prevent cancer.