Open up your medicine cabinet or refrigerator, and you'll likely find them: neglected canisters of multivitamins you bought years ago, thinking, 'It can't hurt; why not?'

And you're not alone: Around half of Americans report regularly taking vitamins or other mineral supplements, according to a 2013 Gallup poll.

Vitamins and dietary supplements are a multibillion-dollar business in the U.S. But research in recent years suggests that you're probably better off forgoing that daily multi altogether.

"We believe that the case is closed: Supplementing the diet of well-nourished adults with (most) mineral or vitamin supplements has no clear benefit and might even be harmful," wrote the authors of an editorial summarizing research published in the Annals of Internal Medicine in 2013.

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Research in three studies — all equally damning — examined the durability of health claims of supplements such as beta carotene; vitamins A, E, and B; antioxidants; and folic acid. Here's what those studies found:

• A study of about 400,000 adults found that healthy people who received daily multivitamins were no less likely than those who didn't to develop cancer or heart disease or to live longer.
• After examining about 6,000 men older than 65, a second study concluded that those who received multivitamins had no better cognitive performance or verbal memory than those who did not.
• A third study looked at 1,700 men and women with history of heart attacks. The authors reported a high dropout rate, but even still, multivitamins appeared to have no preventative effect.

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"Enough is enough: Stop wasting money on vitamin and mineral supplements," the authors concluded in the accompanying editorial.

Research looking into the less-than-reassuring effects of taking multivitamins stretches back years, but there have been few crackdowns on the industry. That is, until recently.

Last year, the U.S. Justice Department filed both civil and criminal complaints against 117 dietary supplement manufacturers amid broader calls for increased regulation of the industry. Many of the products targeted in the investigation included workout supplements found to contain dubious stimulants concocted in Chinese chemical factories, The New York Times reported.

Such products are, of course, different from daily vitamin supplements, which remain popular and enjoy a positive reputation among the general public (not to mention strong support from industry lobbying groups such as the National Products Association and the Council for Responsible Nutrition). It's unclear whether or when that will change.

For its part, the industry has repeatedly defended the effectiveness of its products. It has also argued that people with incomplete diets or "nutrient gaps" can fix any imbalances with supplements.

"While those in the ivory tower may say that people just need to eat their sardines and salads, in the real world there are nutrient gaps," Duffy MacKay of the Council for Responsible Nutrition said in 2013.

Not everyone buys that argument. The Daily Beast reported that it's questionable whether the so-called nutrients in dietary supplements are processed in the same way as nutrients in foods:

"The ingestion of supplements, however, is anything but natural. Although popping 1,000 milligrams of Vitamin C (present in forms as delightful as gummy bears) might seem like no big deal, you would have to eat 14 oranges or eight cantaloupes to achieve the same amount. It’s hard to eat eight cantaloupes at one time."

In any case, the public seems to want supplements. "Sales of multivitamins and other supplements have not been affected by major studies with null results," the authors of the 2013 studies wrote. "We should transplant null and negative findings into action. The message is simple: Most supplements do not prevent chronic disease or death, their use is not justified, and they should be avoided."