First you say it will, and then it won't....

Apparently we need to be perpetually equipped with little sun meters, so we can precisely calibrate the amount of sun that will benefit, without harming us:

Sunlight can reduce a man's risk of prostate cancer, a study suggests. Researchers from three US centres found men exposed to a high amount of sun had half the risk of the disease than those exposed to a low amount. Writing in Cancer Research, they suggest that the protection was a result of the body's manufacture of vitamin D after sun exposure. But men were warned not to sunbathe excessively because of the risk of developing skin cancer.

Men, grab some of your sunscreen and get yourselves out there. Women, I've already heard that a little bit of sun is good for our bones. On the other hand, my Mom, Dad and grandmother all had (thank goodness, not fatal) melanomas, so I'll just cheer you on from the sidelines!