Another reason to skip multivitamins.
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Another reason to skip multivitamins.

There's little question that the standard American diet is lacking in many necessary nutrients: Studies show that 70 percent of people here don't get enough vitamin D, half are low in calcium, and some 48 percent are deficient in magnesium. The answer, for decades, has been clear: Take a multivitamin. "I used to take a multivitamin every day," says Dr. Paul Offit, author of Do You Believe in Magic? The Sense and Nonsense of Alternative Medicine, who has joined a new crusade against the preventative supplements. "But when I started reading [the research], I stopped."

This past December, three major papers gave another blow to advocates of the once-a-day multivitamin. Together they concluded that vitamins do nothing to reduce the overall risk of cancer, incidents of heart disease, or the loss of cognitive skills. These papers add evidence to the case that while a lack of vitamins has long been linked to a variety of health concerns, taking a multivitamin doesn't do much to bridge the gap.

Roughly 30 percent of Americans now take a multivitamin. "When you have such massive use of some product, you'd expect to have a pretty good return on it," says Dr. Eliseo Guallar, a nutrition researcher at Johns Hopkins. "But it seems to us that a return isn't there. They're probably wasting their money."

Some trace our trust in multivitamins back to Linus Pauling, a renowned chemist who, despite having his claims disproved in the New England Journal of Medicine, was an outspoken advocate of taking high doses of vitamins A, C, and E, beta-carotene, and selenium to "cure virtually every disease known to man," according to The Atlantic. There's been a battle over the science behind such advice ever since.

The consensus is edging toward the idea that as a precautionary measure, multivitamins just don't work, and may even pose a risk to our health. Past studies have shown that large doses of beta-carotene and vitamin E increase the likelihood of particular cancers in some people. "If you're influencing human physiology," which vitamins do, says Dr. David Katz, director of the Yale University Prevention Research Center, "and you go too far or do it the wrong way, it has the potential to do harm. At the very best, supplements are supplements to – not substitutes for – living well."

Some experts, like Balz Frei, a professor of biochemistry at Oregon State University, still believe in multivitamins. The vast majority of Americans are lacking in at least a few key vitamins, he says, and a multivitamin is the fastest, cheapest way to fix this.

The best way to get necessary vitamins, most experts, including Frei, agree, is from a healthy, plant-heavy diet. You get a wider range of nutrients that way – with bioflavonoids and antioxidants that keep us healthy. What's more, interacting compounds in the plants help the body absorb some nutrients better. That's why it's important that an array of fruits and vegetables make up half of every meal; different colors often correlate with different nutrients.