Health myth: Do you really need to take a multivitamin?

(iStock)

Your multi-v isn't a miracle pill, but could it actually be dangerous?

Follow the money and you'll find it going into the cushy pockets of the supplement industry, now estimated to be a $30 billion behemoth—and that's just for the U.S., where more than half of adults use dietary supplements and about 40 percent pop a multivitamin every day.

Enter "Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements," a recent Annals of Internal Medicine editorial that's threatening the industry's bottom line. The authors (who hail from Johns Hopkins, the University of Warwick, and the American College of Physicians) examined the benefits of existing studies on multivitamins and found that, really, there are none.

DETAILS: 14 Healthiest Snack Foods You Can Buy

"We believe that the case is closed," wrote the researchers. "These vitamins should not be used for chronic disease prevention. Enough is enough."

Christopher Ochner, Ph.D., research associate at the New York Obesity Nutrition Research Center at St. Luke's and Roosevelt Hospitals, takes it one step further. "Taking a daily multivitamin is actually associated with an increase in all-cause mortality," he says.

DETAILS: Foods That Will Make You Look Younger

In fact, previous studies from the University of Minnesota, the Cleveland Clinic, and myriad other institutions that go back to the 1940s link vitamin intake to cancer, heart disease, and premature death rates.

While vitamin E supplementation has been linked to a higher risk of lung cancer in smokers, in the case of multivitamins, chances are it's an association, rather than a strict cause-and-effect relationship, that's shortening lives. It's possible that people who take multivitamins are health worrywarts, stressed out, or perhaps suffering the consequences of poor mental health. Or maybe they're just relying on a little capsule to make up for a diet based on junk food.

DETAILS: Do You Really Need to Wear Sunscreen in the Winter?

That's why Ochner recommends simply eating a balanced diet. "It's really not that hard to get what you need," he says. If you hit all of your food groups, you're pretty much set. Your body even helps out by converting some nutrients and food compounds into other ones your body needs, he says.

Unless you have some sort of condition that sends your body's vitamin and nutrient levels out of whack (gastric bypass surgery, for instance, can lead to temporary vitamin malabsorption), multivitamins are really just the ingredients for really expensive urine, he says. Your body can use only so much of every nutrient, and once you surpass those limits, they're literally flushed from your body. "The concept of 'a little is good, more must be better' just doesn't apply here," he says.

DETAILS: 7 Childhood Actors Who Made It Big

Still, it's worth mentioning that if you're deficient in a certain vitamin or nutrient (a simple blood test from your primary-care doc can determine if you are), you shouldn't just keep doing what you're doing. And while the first remedy should always be dietary changes, multivitamins can help shore up weak spots, he says.

Take care in the supplements aisle: Since Congress defines supplements as food, not drugs, they don't have to receive FDA approval and the manufacturer—who, let's face it, is probably more concerned with his bottom line than your health—is responsible for their contents. While Ochner says you generally get what you pay for when it comes to vitamins, you can also log on to Emerson Ecologics to verify different brands' credibility and buy vitamins. All of the companies listed on the site allow independent analytical testing of their products and audits of their facilities.

DETAILS: The Top 7 Trends from Spring 2014

Additional sources: Colorado State University and the Centers for Disease Control and Prevention.