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What Taking a Vitamin Every Day Does to Your Body

It's not all good.

When it comes to our health, just about everyone is looking for an extra boost—particularly during the COVID-19 pandemic. That desire has helped vitamins and supplements grow into a $150 billion worldwide industry. If you're considering taking a daily vitamin—or are taking one now—it's important to know there are clear things vitamins can and can't do, as indicated by decades of research. And if you take them the wrong way, they can be harmful. Read on to find out what taking a daily vitamin does to your body—and to ensure your health and the health of others, don't miss these Sure Signs You May Have Already Had COVID.


It Can Help Fill Nutritional Gaps

Woman taking her medication in her bedroom at home.

"If you're like everybody else in the world, and you don't eat a perfect diet every day, a multivitamin is going to fill in the little deficits you have on a daily basis," Kathryn Boling, MD, a family medicine doctor with Mercy Medical Center in Baltimore, told ETNT Health. "And if you're OK paying money for something that you're mostly going to pee out, but it's going to fill in those tiny little deficits, then take a multivitamin. I do." 

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It May Enhance Your Immunity

vitamin d

If your daily multivitamin contains vitamins C and D (and most do), those nutrients may support your immune system. "If you're deficient in vitamin D, that does have an impact on your susceptibility to infection," said Dr. Anthony Fauci, the nation's top infectious-disease specialist, in an interview last fall. "I would not mind recommending—and I do it myself—taking vitamin D supplements." 

He added: "The other vitamin that people take is vitamin C because it's a good antioxidant, so if people want to take a gram or so of vitamin C, that would be fine." 

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It May Give You A False Sense of Security

Man sitting at the table and taking vitamin D

You might erase potential benefits from vitamins if you chase them with soda and sugary snacks, or use them as justification for too many cheat meals. "Supplements are never a substitute for a balanced, healthful diet," said Dr. JoAnn Manson, a preventative medicine specialist, in an interview with Harvard Health. "And they can be a distraction from healthy lifestyle practices that confer much greater benefits."

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You Might Make Yourself Sick

young woman with stomach pain
Shutterstock / PR Image Factory

If your vitamin contains high doses of certain nutrients, that can cause problems. Most vitamins are water-soluble, meaning they can't build up in the body because any excess is cleared by urine. But fat-soluble vitamins — including A, D, E and K — can build up in the body and may be dangerous at high levels, particularly A and E.

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It Won't Be a Magic Bullet

Shot of woman nutritionist doctor writes the medical prescription for a correct diet on a desk with fruits, pills and supplements.

If you're taking multivitamins for protection against serious disease, you should know that the science isn't quite there yet. In 2018, researchers from Johns Hopkins analyzed studies involving almost half a million people; they determined that taking multivitamins doesn't lower your risk of heart disease, cancer, cognitive decline, or early death. Their advice: Don't waste your money on multivitamins—get the vitamins and minerals you need from food. And to get through this pandemic at your healthiest, don't miss these 35 Places You're Most Likely to Catch COVID.

Michael Martin
Michael Martin is a New York City-based writer and editor. Read more about Michael