The global distribution of many types of cancer is strongly related to latitude. The farther you are from the equator, the higher the rate of disease. The more sun you get, the less cancer. It's hard not to infer that sun exposure and thus synthesis of vitamin D helps prevent many cancers.

We've been urged to avoid sun exposure because it can cause skin cancer. But those cancers are squamous and basal cell carcinomas. Those carcinomas are easily cured, and don't usually kill you. Melanoma, the truly deadly skin cancer, is more prevalent in populations with less sun exposure.

There are lots of interesting graphs on Jeff Bowles' site [^1]. He's an absolute fan of vitamin D.

^1:https://jefftbowles.com/vitamin-d3-deficiency-causes-most-hu...