Just as the message is starting to sink in that the only safe tan is a fake one, along comes the news that soaking up a little sunshine here and there might actually strengthen your immune system.

What? Yes, you heard right. Researchers noticed that while rates of skin cancer -- as well as several other types of cancer -- tend to be higher in sunnier latitudes, patients in these regions seem to fare better when it comes to fighting the disease. Their secret defense? Might be the extra vitamin D they score from living in a sunnier clime. Your body converts inactive vitamin D to active vitamin D when your skin is exposed to strong sunlight. "D" stands for defense: This vitamin turns on a gene that checks your DNA for errors and kills cells -- like cancer cells -- that have them.

Your body activates vitamin D from the sun faster and more effectively than it soaks it up from food and supplements. But you know the trouble with that: Sunlight is great for growing plants and yellowing newspapers, but it leaves your skin vulnerable to skin cancer and wrinkles, and inflammation from burns needlessly uses up your stem cells (better to have them to repair things like your heart, kidney, or brain).

So what to do? Get some sun, but only a little bit. Just 10 to 20 minutes of summer sun gets you the D you need for the day (in much of North America, winter sun isn't strong enough to get D production going). Or use sunscreen and rely on vitamin D supplements. Take 1,000 international units (IU) of D3 every day if you're under age 60 and 1200 IU a day if you're over 60.

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