That said, new research suggests that vitamin D — which the body produces with the help of sunlight — may protect against a host of cancers, namely colon, breast, prostate, endometrial, and ovarian. A study published in January 2008 in the Journal of Epidemiology and Community Health showed a link between lung cancer rates and sun exposure, with greater rates of lung cancer in countries farther from the equator. “Smoking accounts for 90 percent of lung cancers,” says study author Cedric F. Garland, DrPH, epidemiology professor at the University of California, San Diego. “We believe vitamin-D deficiency accounts for the remaining 10 percent.”

He recommends getting a blood test to determine your vitamin-D levels. “It's as important as getting your cholesterol checked,” says Garland. To boost your levels: Strip down to shorts and a halter — you want 40 percent of your skin showing — and a floppy hat. Soak up the rays for between 5 and 20 minutes, depending on your skin type (the fairer you are, the shorter the duration). For some people (green-eyed, red-headed Celts, like me), the risk of skin cancer may outweigh the benefits of sunshine-induced vitamin D. Backup plan: Take a vitamin D3 supplement in the amount of 1,000-2,000 IU a day. Although vitamin D is found in food sources, Garland says, you'd have to drink ten to 20 glasses of milk a day to get a sufficient dose.