Are you among the one in three Americans who gulps down a multivitamin every morning, probably with a sip of water? The truth about this popular habit may be hard to swallow.

“Most people would be better off just drinking a full glass of water and skipping the vitamin,” says Pieter Cohen, an associate professor of medicine at Harvard Medical School and an internist at Harvard-affiliated Cambridge Health Alliance. In addition to saving money, you’ll have the satisfaction of not succumbing to misleading marketing schemes.

That’s because for the average American adult, a daily multivitamin doesn’t provide any meaningful health benefit, as noted recently by the US Preventive Services Task Force (USPSTF). Their review, which analyzed 84 studies involving nearly 700,000 people, found little or no evidence that taking vitamin and mineral supplements helps prevent cancer and cardiovascular disease that can lead to heart attacks and stroke, nor do they help prevent an early death.

“We have good evidence that for the vast majority of people, taking multivitamins won’t help you,” says Cohen, an expert in dietary supplement research and regulation.

Who might need a multivitamin or individual supplements?

There are some exceptions, however. Highly restrictive diets and gastrointestinal conditions, or certain weight-loss surgeries that cause poor nutrient absorption, are examples of reasons why a multivitamin or individual vitamins might be recommended. A daily vitamin D supplement may be necessary when a person gets insufficient sun exposure. Your doctor may recommend an iron supplement if you have a low red blood cell count (anemia).

Why is it hard to give up the habit of a daily multivitamin?

Surveys suggest people take vitamins to stay healthy, feel more energetic, or gain peace of mind, according to an editorial that accompanied the USPSTF review. These beliefs stem from a powerful narrative about vitamins being healthy and natural that dates back nearly a century.

“This narrative appeals to many groups in our population, including people who are progressive vegetarians and also to conservatives who are suspicious about science and think that doctors are up to no good,” says Cohen.

Unproven marketing claims for dietary supplements

Vitamins are very inexpensive to make, so the companies can sink lots of money into advertising, says Cohen. But because the FDA regulates dietary supplements as food and not as prescription or over-the-counter drugs, the agency only monitors claims regarding the treatment of disease.

This is an excerpt from an article that appears on the Harvard Health Publishing website.

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Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine.