All you have to do is sunbathe for a few hours once a month to get an adequate dose of vitamin D, say the doctors. But, dermatologists are horrified at the suggestion. The risk of skin cancer doesn't make it worthwhile, they argue. So, what is the solution .... Let's say you try to cat right. And take a multivitamin, chased by a glass of fortified milk. But unless you're a sunbather, and no one's suggesting you should be, odds are good that you're seriously lacking in vitamin D. New research says that not getting enough vitamin D can hike your risk not only of bone fractures and osteoporosis, but also of several types of cancer and a range of autoimmune conditions, including rheumatoid arthritis and multiple sclerosis.

"Until recently, we defined vitamin D adequacy as not having rickets," says Robert Heaney, an osteoporosis researcher at Creighton University in Omaha, Nebraska. Rickets is a childhood bone-softening condition rarely found in this country. "We've suddenly become more alert to what's going on." The emerging evidence about D's wide-ranging health effects has unleashed a heated debate. On one side are the vitamin D researchers who contend that the federal (U.S.) government has grossly understated how much vitamin D people need. Given the near-absence of food sources, they say many people probably need to spend more time in the sun. Sunlight causes the body to produce vitamin D. On the other side is the dermatology community, which for years has campaigned against sunbathing and in favour of the sunscreen. Many dermatologists fear that more sun exposure will only swell the U.S.' ballooning rate of skin cancer. "I think it's wrong-headed, and there's going to be a problem down the road with tumours and sun damage," says Mark Naylor. He's a tumour biologist at the Oklahoma Medical Research Foundation in Oklahoma City. "I think most people get enough sun exposure to get sufficient vitamin D."

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