Dietary supplements are a $37 billion a year business, according to the National Institutes of Health, but there’s mounting evidence that vitamin and mineral supplements aren’t effective in preventing chronic diseases or in slowing their progression.

What’s more, some nutrients may be harmful if taken in large doses, studies have suggested. One of the most recent, published recently in JAMA Internal Medicine, found that high doses of vitamin D were associated with a higher risk of falls in men and women 70 years and older, compared with lower doses.

Multivitamins are the most commonly used dietary supplements, accounting for $5.7 billion in annual sales, according to the National Institutes of Health. “If you want that feeling of having a safety net below you, multivitamins are kind of that,” said Katherine Zeratsky, a registered dietitian nutritionist at the Mayo Clinic in Rochester, US. That said, she noted, people should try to get their nutrients from food first.

While multivitamins may make up for any shortfalls in the diet, they don’t guarantee future health. For example, a 2013 study published in the Annals of Internal Medicine found that long-term use of a daily multivitamin did not provide cognitive benefits to older men.
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