There’s a great article in the NYT health section on the science behind health effects of vitamin D supplements.

Imagine a treatment that could build bones, strengthen the immune system and lower the risks of illnesses like diabetes, heart and kidney disease, high blood pressure and cancer.

Some research suggests that such a wonder treatment already exists. It’svitamin D, a nutrient that the body makes from sunlight and that is also found in fish and fortified milk[…]

But don’t start gobbling down vitamin D supplements just yet. The excitement about their health potential is still far ahead of the science.

Although numerous studies have been promising, there are scant data from randomized clinical trials. Little is known about what the ideal level of vitamin D really is, whether raising it can improve health, and what potential side effects are caused by high doses.

Knowing the short attention span of Americans, I’m a little worried people will only read the first 3 paragraphs and think that vitD will cure all their ills, but the article does a great job of explaining that while there is some evidence of correlation between vitD levels and health,

“People may have high vitamin D levels because they exercise a lot and are getting ultraviolet-light exposure from exercising outdoors,” Dr. Manson said. “Or they may have high vitamin D because they are health-conscious and take supplements. But they also have a healthy diet, don’t smoke and do a lot of the other things that keep you healthy.”

I can’t complain when readers are reminded that correlation does not equal causation. Dr. Manson is here at Harvard, and is embarking on an ambitious clinical trial to determine whether vitD supplements actually do anything. More research into this stuff is great. Anyone who was at last year’s Flu lecture from Science in the News probably remembers the guy that went on for 5 minutes on how necessary vitD supplements were – it would have been nice to have some real data to back up (or refute) his claims.