Comment by dsizzle

The article did describe some mechanisms, for instance the skin uses UV to make nitric oxide, which is known to lower blood pressure. That said, I'm not sure why this would be better than just taking nitric oxide. The same question comes up for vitamin D, and it's noted that supplements don't seem to help there -- with no explanation for that. So I would agree that the explanations for the pro-sunlight case are weaker.