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6 Vitamin Myths You Have to Stop Believing—and 2 Vitamins You Actually Do Need

Taking vitamins you don't need isn't just a waste of money—it could put your health at risk, too.

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Myth: Anyone could benefit from a multivitamin

In the early 1900s, vitamin-deficiency diseases weren’t unheard-of: These days, you’re extremely unlikely to be seriously deficient. Most packaged foods are vitamin-enriched. Sure, most of us could do with a couple more daily servings of produce, but a multi doesn’t do a good job at substituting for those. “Multivitamins have maybe two dozen ingredients—but plants have hundreds of other useful compounds,” says Marian Neuhouser, PhD, of the cancer prevention program at the Fred Hutchinson Cancer Research Center in Seattle, Washington. “If you just take a multivitamin, you’re missing lots of compounds that may be providing benefits.” Don’t miss these other 8 vitamins that are useless, if not dangerous.

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Myth: A multivitamin can make up for a bad diet

An insurance policy in a pill? If only it were so. One study in the Archives of Internal Medicine looked at findings from the Women’s Health Initiative, a long-term study of more than 160,000 midlife women. The data showed that multivitamin-takers are no healthier than those who don’t pop the pills, at least when it comes to the big diseases—cancer, heart disease, stroke. “Even women with poor diets weren’t helped by taking a multivitamin,” says study author Dr. Neuhouser. Here are 12 more vitamin mistakes you didn’t know you were making.

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Myth: Vitamin C is a cold fighter

In the 1970s, Nobel laureate Linus Pauling popularized the idea that vitamin C could prevent colds. Today, drugstores are full of vitamin C–based remedies. But don’t get dragged in to the hype. In 2013, researchers analyzed a raft of studies going back several decades and involving more than 11,000 subjects to arrive at a disappointing conclusion: Vitamin C didn’t ward off colds, except among marathoners, skiers, and soldiers on subarctic exercises. The nutrient might help you heal from a cold a day faster, but taking C only after symptoms crop up doesn’t help; researchers conclude that patients can decide for themselves whether year-round pill-popping for minimal benefit is worth the money.

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Myth: Vitamin pills can prevent heart disease

At one point, researchers hoped antioxidant vitamins like C, E, and beta-carotene could prevent heart disease by reducing the buildup of artery-clogging plaque. B vitamins were promising, too, because folate, B6, and B12 help break down the amino acid homocysteine—and high levels of homocysteine have been linked to heart disease. Unfortunately, none of those hopes have quite panned out. An analysis of seven vitamin E trials concluded that it didn’t cut the risk of stroke or of death from heart disease. The study also scrutinized eight beta-carotene studies and determined that, rather than prevent heart disease, those supplements produced a slight increase in the risk of death. The same is true of the other promising vitamin candidates. Instead of taking pills, the American Heart Association recommends eating a varied diet rich in fruits, vegetables, and whole grains. Don’t miss these other secrets vitamin manufacturers are keeping from you.

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Myth: Taking vitamins can protect against cancer

Researchers know that unstable molecules called free radicals can damage your cells’ DNA, upping the risk of cancer. They also know that antioxidants can stabilize free radicals, theoretically making them much less dangerous. So why not take some extra antioxidants to protect yourself against cancer? Because research so far has shown no good comes from popping such pills. A number of studies have tried and failed to find a benefit, like one that randomly assigned 5,442 women to take either a placebo or a B-vitamin combo. Over the course of more than seven years, all the women experienced similar rates of cancers and cancer deaths.

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Myth: Hey, it can’t hurt

The old thinking went something like this—sure, vitamin pills might not help you, but they can’t hurt either. However, a series of large-scale studies has turned this thinking on its head, says Demetrius Albanes, MD, a nutritional epidemiologist at the National Cancer Institute. The shift started with a big study of beta-carotene pills. It was meant to test whether the antioxidant could prevent lung cancer, but researchers instead detected surprising increases in lung cancer and deaths among male smokers who took the supplement. Then a ten-year study from 2017 looking at more than 77,000 adults over 50 found that vitamin B6 and B12 supplements increased lung cancer risk for men (though not for women). Other studies have raised concerns that taking high doses of folic acid could raise the risk of colon cancer. The bottom line: Vitamins are safe when you get them in food, but in pill form, they can act more like a drug, Albanes says—with the potential for unexpected and sometimes dangerous effects.

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Truth: A vitamin D supplement could do you good

Despite the negative research on supplements, one pill is looking better and better. Vitamin D seems to protect 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. 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 (which is a good thing!) and workaholic (or TV-aholic) habits, most people don’t make enough. To make up for it, the NIH recommends most adults aim to get 600 IU of vitamin D every day, or 800 IU after age 70.

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Truth: Women planning to have a baby should pop a vitamin

There is one group that probably ought to keep taking a multi-vitamin: future moms. A woman who gets adequate amounts of the B vitamin folate is much less likely to have a baby with a birth defect affecting the spinal cord. Since the spinal cord starts to develop extremely early—before a woman may know she’s pregnant—the safest course is for her to take 400 micrograms of folic acid (the synthetic form of folate) daily when she’s trying to get pregnant. Folic acid isn’t necessary for the rest of the population, though. Less than 1 percent of Americans—including women of reproductive age—are folate deficient, partially thanks to requirements that all enriched cereal grain products get a boost of folic acid, according to the CDC.