In the world of dietary supplements, manufacturers sell products with relatively few regulations. It turns out this freedom is putting consumers at risk. A new study is the first to shed light on the effects of dietary supplements by revealing just how many injuries and hospitalizations are tied to the $32 billion a year industry. Thousands of people end up in the emergency room every year because of dietary supplements, many of them suffering heart problems related to taking weight loss or energy supplements.

For the study, researchers from the Food and Drug Administration (FDA) collaborated with the Centers for Disease Control and Prevention to comb through data involving dietary supplement-related visits to 63 emergency departments from 2004 to 2013. They calculated that there were between 18,611 and 27,398 emergency room visits every year due to adverse effects, including heart problems, allergic reactions, nausea, and vomiting. In one year alone, 2,150 of the cases were serious enough to require hospitalization.

Patients, who wound up in the ER for alarming reactions to dietary supplements took products ranging from herbal pills and amino acids to vitamins and minerals. More than a quarter of the ER visits documented in the study were by young adults between the ages of 20 and 34 years, half of whom took supplements that advertised weight loss and energy enhancement. They most commonly experienced chest pain, heart palpitations, and irregular heart rhythms.

While the number of people who take supplements and experience adverse effects is relatively small (5 percent), the unregulated market continues to grow. Shelf after shelf, dietary supplements are adding up in stores. More than half of adults in America report using at least one dietary supplement in the past month.

FDA Approval, Or Lack Thereof

In 1994, the FDA put into effect a law that essentially considers supplements safe until proven otherwise. As a result, dietary supplement manufacturers are not required to have their products approved by the FDA before selling them on the shelves of your local drug store. All dietary supplement manufacturers have to do is report that the products were safe in tests, that the claims they’ve made about the products are not false or misleading, and that they comply with FDA regulations.They’re generally only pulled from shelves once complaints of serious injuries are reported.

A recent 2014 study published in the Journal of the American Medical Association found approximately two-thirds of the more than two dozen dietary supplements that the FDA recalled between 2009 and 2012 ended up back on the market a year later. Those supplements, the study found, still contained many of the same pharmaceutical ingredients that were banned after they were shown to increase the risk of heart attack and stroke.

Source: Budnitz DS, Geller AI, Shehab N, et al. Emergency Department Visits for Adverse Events Related to Dietary Supplements. The New England Journal of Medicine. 2015.