One contradictory study is not enough to convince me that all the other data is incorrect. First of all, the people's sun exposure was "self reported" and self reporting is notoriously unscientific. Second, they didn't say how much of the body was exposed to the sun. You have to expose more than your hands and face to sunlight to receive the full dose of skin-generated vitamin D. Third, people with darker skins block more rays with melanin (skin pigment) and I suspect make less vitamin D per exposure as a result. There are lots of dark-skinned tribal people in Hawaii, but the study doesn't mention that. So frankly, I don't trust this study, and think that more work must be done to find out why they got the result they did.

Best parts to put in the sun are the whitest parts. I have read that in 15 minutes of sun exposure, a white naked body can produce 10x the RDA of Vitamin D. So I'm still putting my white bootie in the rays, and it feels good enough for me to believe it IS good for me.