Today on BodyTalk Dr. Greg Plotnikoff will answer your questions about vitamin D — how to get enough and what happens when you don’t.

Plotnikoff,  medical director of the Institute for Health and Healing at Abbott Northwestern Hospital, may know a lot about health care, but he’s obsessed with vitamin D.  It’s far more than your run of the mill nutrient. It regulates hundreds of genes, and not getting enough of it has been linked to more than dozen different kinds of cancers and many other diseases.

Those of us who live up here on the tundra are especially vulnerable, because it’s just not possible to get enough vitamin D from the sun in the winter. Even in summer, slathering sun screen on you and your loved ones blocks UVB rays — and vitamin D.

But how much is enough? How do you balance too much sun with not enough? What’s a redhead to do? We all need supplements, especially in winter, but how many pills should you take? And infants?

Ask Dr. Vitamin. You can post question anytime, and he’ll share his wisdom here this afternoon starting around 1 p.m.

Are you confused by sunscreens? I am. S.P.F., UVA, UVB, wide spectrum, sweat resistant, waterproof, Mexoryl SX, avobenzone, titanium dioxide and zinc oxide.

Whew.

Now there’s help. The Environmental Working Group has posted a data base of 1,000 or more ratings on different sun screen products. They rate them for how well they block both UVA and UVB rays, plus what kinds of chemicals they contain. You choose among the top ten products (none of which I’ve ever seen at Target), the top ten widely available products, or check out the brand you like best.

The site will also ask you to send a letter to the Food and Drug Administration urging it to update its sun screen standards — which haven’t been updated in 30 years. The new ones may include better ratings for both UVA and UVB, provide better information on how to apply it, and limit the claims that can be made. The FDA said it expects an update soon. In the meantime, though, you can learn a lot about what’s in sunscreen by perusing the Environmental Working Group’s research.