It might be time to rethink your vitamin habit.
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More than half of American adults pop some kind of vitamin pill every day — and maybe you're one of them. But have you ever stopped to consider what that vitamin is actually doing for you?

The truth is that we need vitamins to be healthy — our bodies can't function without them. But that doesn't mean they're harmless. There are times when vitamin pills can be unhelpful or even dangerous.

So INSIDER spoke with dietitian Andy Bellatti, MS, RD, to sift through myths and misinformation and ask all your most embarrassing vitamin-related questions. Here's what you need to know:

Vitamins are substances your body needs to function properly.



"By definition, a vitamin is essential," Bellatti told INSIDER. That means your body needs them but can't make them on its own, so you have to get them from food or supplements. One exception is vitamin D. It's in some food, like egg yolks and fatty fish, but your body also makes it when your skin is exposed to the sun.

Vitamins perform a whole bunch of different functions in your body, from assisting in bone growth to helping convert food into energy. Here's a detailed list of each vitamin's main duties, if you're curious.

You should get your vitamins primarily from food.

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Technically, Bellatti said, vitamins that exist naturally in food work the same as synthetic ones in supplements and pills.

But getting your vitamins from food is still preferred, he said. In whole foods, vitamins come prepackaged with other beneficial substances, like fiber and phytonutrients. These are the natural compounds that give plants their colors, flavors, and texture — growing evidence suggests that they can keep us healthy and prevent diseases.

"A lot of times that vitamin works synergystically with other nutrients," Bellatti explained. You can't replicate that synergy with a supplement, and — as you'll read below — the high vitamin doses found in some supplements can actually be harmful.

"Diet rules the day," Bellatti said. "At the end of the day, supplements can, at best, be a safety net."

But there are some cases where a vitamin supplement is needed.

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Bellatti recommends that people who live at northern latitudes take 1,000 to 2,000 IU of Vitamin D every day during the winter months. In the US, if you live anywhere north of San Francisco, your skin produces little to no vitamin D during the winter, according to the Harvard School of Public Health.

He also recommends daily B12 for vegans and sometimes vegetarians, since B12 is only found in animal-based foods like meat, eggs, and dairy.

Finally, the National Institutes of Health says that women who are pregnant or trying to get pregnant should take 400 micrograms (mcg) of folic acid every day. It can reduce the risk of some birth defects.

If you're unsure about whether you need a supplement, ask a doctor or a registered dietitian.

You probably don't need a multivitamin.


Roughly 40% of Americans take a multivitamin — but they might be just wasting their money. Scientists say there's no strong evidence to back up the belief that taking multivitamins makes you healthier.

"Most supplements do not prevent chronic disease or death, their use is not justified, and they should be avoided," a group of researches wrote in a 2013 editorial for the Annals of Internal Medicine. The authors also addressed multivitamins specifically, writing that evidence shows "no substantial health benefit" to taking a multivitamin.

Bellatti said he's not a fan of multivitamins either, and worries that some people might use them as a license to eat junk food instead of vitamin-rich whole foods. But remember: Vitamins aren't the only thing that makes a diet healthy or unhealthy. Most junk food is still loaded with excess sugar, salt, and unhealthy fat, and popping a multivitamin don't erase those foods' negative qualities.

Yes, you can overdose on vitamins.

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Too much of anything can be toxic at a certain point — even water. Getting too much of a vitamin is harmful, too.

First, it's helpful to understand the two different types of vitamins: Water-soluble and fat-soluble.

All of the B vitamins and vitamin C are water-soluble, meaning that any excess your body doesn't need is flushed out in your urine. Your body doesn't store them. But fat-soluble vitamins (that's A, D, E, and K) are a different story. They're stored in your liver and in fatty tissue throughout your body for long periods of time. That's why overdose is more likely to happen with fat-soluble vitamins, Bellatti explained.

Overdoing it on vitamin A can lead to dizziness, nausea, headaches, coma, and death, for example, and too much vitamin D can cause nausea, vomiting, constipation, weakness, and weight loss. There's also evidence that supplementing with A and E could increase the risk of death.

The good news is that it's very tough to OD on vitamins that come from whole, natural foods in your diet. The main concern is supplements or pills that have super high doses of vitamins, or foods that have been fortified with large doses of synthetic vitamins.

Almost every vitamin has what's known as an upper limit, or a daily amount that's safe to consume, Bellatti said — you can find all of them in this handy chart. If you are taking a supplement, make the dose is low enough that it's not putting you over that daily upper limit.

Taking vitamin C won't help your cold.

Don't waste your money on this.
Flickr/Mike Mozart

You know all those vitamin C supplements that claim to "support" your immune system? They're not going to help you get over a cold faster.

Back in 2007, researchers pooled the results of 29 different trials looking at the effect of vitamin C on colds. They found that taking 200 mg of vitamin C every single day — not just on days when you're sick — could shorten the length of a cold by about one day.

But starting a vitamin C supplement once you already have a cold won't do anything. The review concluded it's no better than a placebo.

"After the cold is running its course, [vitamin C] doesn't have any effect," Bellatti said. "If you do have a cold, stay hydrated and get enough rest. Don't go to work and pound Emergen-C."

Vitamins can't give you more energy.

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You've probably come across a bottle of B vitamin pills that promises to "boost" your energy. That's impossible.

B vitamins are part of the complex chemical process your body uses to convert food into energy. But the vitamins themselves can't actually give you a boost.

"The one [misconception] I've heard for decades now is that vitamins give you energy," Bellatti said. "There's no way in which vitamins can give you energy. Only calories can do that." (By the way: Here are 7 answers to your most embarrassing calorie questions.)

Adding vitamins to a junk food doesn't make it healthy.

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Just because a food is pumped full of vitamins, doesn't automatically make it a great choice. One example: vitamin-infused waters, which typically pack dozens of grams of added sugar. Bellatti described them as "Kool-Aid with vitamins."

It's better to look past those flashy front-of-package claims about vitamin content. They're not telling you the full story about a food.

"The front of the package is all marketing — ignore it," Bellatti said. "The back of the package is science."

Before you buy vitamins, take a peek at the Nutrition Facts and the ingredients list. Bellatti recommends packaged foods that have some fiber, but minimal added sugar. Here's a helpful guide to decoding nutrition labels.

If you are truly deficient in a vitamin, you'll have concerning symptoms.


It's unlikely that you'd have a serious vitamin deficiency without realizing something was off.

Vitamin C deficiency causes scurvy, for example, and vitamin B12 deficiency can cause fatigue, tingling hands and feet, and even confusion and memory loss.

"A true vitamin deficiency will always have symptoms," Bellatti said.

If you're worried that you're getting sub-optimal levels of a certain vitamin or nutrient, always talk with a doctor or a registered dietitian.