As studies have eroded the hopes placed in most vitamin supplements, one pill is looking better and better. Research suggests that vitamin D protects against a long list of ills: Men with adequate levels of D have about half the risk of heart attack as men who are deficient. And getting enough D appears to lower the risk of at least half a dozen cancers; indeed, epidemiologist Cedric Garland, MD, at the University of California, San Diego, believes that if Americans got sufficient amounts of vitamin D, 50,000 cases of colorectal cancer could be prevented each year.
But many—perhaps most—Americans fall short, according to research by epidemiologist Adit Ginde, MD, at the University of Colorado, Denver. Vitamin D is the sunshine vitamin: You make it when sunlight hits your skin. Yet thanks to sunscreen and workaholic (or TV-aholic) habits, most people don’t make enough.
How much do you need? The Institute of Medicine is reassessing that right now; most experts expect a big boost from the current levels (200 to 600 IU daily). It’s safe to take 1,000 IU per day, says Ginde. “We think most people need at least that much.”