Frequent shoppers are healthier

An interesting article published in the April 2011 issue of J Epidemiol Community Health, Frequent shopping by men and women increases survival in the older Taiwanese population, is not too surprising. I didn't see the full article (not published yet?). But I think the reason frequent shoppers are healthier may be that they walk and use brains a lot, contributing to improvement of physical and mental health. What's a little surprising is the finding that "Highly frequent shopping may favour men more than women". Is it because shopping frequency varies much more among men than among women?

Sun UV to trigger Vitamin D and skin cancer: intensity matters?

I've never read a report about this but I have had this suspicion for a long time. On the one hand, we need to expose our skin to the sunlight, preferably on a daily basis, in order to let the body synthesize enough vitamin D. On the other, we don't want so much exposure as to cause skin cancer. All reports or articles I know simply advise moderation in exposure time. But I have a hypothesis that intensity, or rather, local intensity multipled by time of exposure, matters more. Suppose the UV light coming to your skin is x lux's in intensity and it lasts y seconds. The chance of you getting skin cancer on that spot is proportional to x*y. If this hypothesis is true, then we have a good strategy to achieve both goals at the same time, getting enough UV and avoiding skin cancer: alternate the part of your body exposed to the sun, and never let the sun light come to one small part of the skin for an extended period of time.

[Update]
Also see

Is there too much radiation from X-ray exams?