Humans can synthesize vitamin D on their own, but they also need to be exposed to UV light (most commonly administered as a part of daylight) in order to be able to do it...
> Melanoma? True, the sun worshippers had a higher incidence of it—but they were eight times less likely to die from it.[1]
1. https://www.outsideonline.com/health/wellness/sunscreen-sun-...