Dietary supplements are responsible for an estimated 23,000 visits to hospital emergency rooms, and more than 2,100 hospitalizations, in the United States each year, a new study reveals.

Researchers found that more than one-quarter of these emergency visits involved young adults ages 20 to 34, and about one-fifth of them involved unsupervised children who swallowed adult supplements, according to the study, which was published online today (Oct. 14) in the New England Journal of Medicine.

The visits involved people who had taken herbal, homeopathic and nutritional supplements, such as amino acids and probiotics, as well as vitamins and minerals, according to the study.

Prior to these estimates, there was little national data on the safety of dietary supplements aside from the information that researchers could glean about the several hundred supplement products that have been recalled by the Food and Drug Administration for containing unapproved ingredients or contaminants, said Dr. Andrew Geller, the study's lead author and a medical officer with the Centers for Disease Control and Prevention's Division of Healthcare Quality Promotion in Atlanta.

To determine the number of Americans who may have experienced harmful consequences of dietary supplements — such as unwanted side effects, allergic reactions, excess doses and accidental swallowing by children — the researchers analyzed data gathered from 63 U.S. hospital emergency rooms between 2004 and 2013. [7 Bizarre Drug Side Effects]

Over the 10-year period, there were about 3,700 ER visits at these hospitals, including 400 cases in which the person was admitted to the hospital, the researchers found. From these numbers, they calculated the new national yearly estimates.

However, the estimated 23,000 emergency room visits and 2,100 hospitalizations per year are "likely an underestimate of adverse events," Geller told Live Science.

One reason the estimates may be on the low side is that many people who have negative reactions to a dietary supplement never end up in a hospital emergency room, he said. Instead, they might see their doctors, go to walk-in clinics or self-treat the problem at home, and none of these examples would be captured in the new study.

Another reason the findings might be an undercount is that some commonly used forms of dietary supplements, such as protein shakes and energy drinks, were not included in the analysis because they are considered foods.

And a third reason is that patients don't consistently report their use of dietary supplements to health professionals, or they cannot remember the exact brand they used, Geller said. This makes it hard for health practitioners to draw a connection between the symptoms a person is experiencing and a supplement's possible side effects. 

Harmful effects

Although the harmful effects linked with dietary supplements account for less than 5 percent of those caused by pharmaceuticals and over-the-counter medications, there are reasons to be concerned as more Americans turn to supplements in attempts to improve their health, Geller said.

Unlike prescription drugs, dietary supplements are not required to undergo safety testing or FDA approval before they are marketed to consumers.

In the study, the researchers pointed out that although young adults are typically considered a healthy group, this age group made the most emergency room visits because of adverse reactions to dietary supplements.

Young adults were involved in 28 percent of the cases of negative reactions to dietary supplements. In comparison, 22 percent of cases involved kids younger than 4, and 15 percent involved adults ages 35 to 49. Just 12 percent of cases involved people over 65.

Many young adults don't realize that dietary supplements can cause side effects, Geller told Live Science.

The analysis showed that weight loss and energy supplements accounted for more than half of the cases in 20- and 30-somethings. People in this group experienced heart palpitations, chest pain and a racing heartbeat after using these two types of supplements.

The most common problems seen in people over 65 were swallowing problems caused by vitamins and minerals, the study found. Older adults were more likely to report choking or feeling the sensation of a pill being stuck in their throat.

However, the findings were unable to link specific harms to specific ingredients in the supplements, Geller said.

Now that some of the at-risk groups have been identified, the next steps will be to focus on prevention efforts that can reduce the number of harmful effects from dietary supplements, Geller said.

This means educating parents and other caregivers to store dietary supplements and medications out-of-sight and away from young children, Geller said.  

He also recommended that older adults take dietary supplements with plenty of water or other fluids, and to ask their doctor or pharmacist whether a large supplement can be cut in half or comes in a liquid form. 

Geller encouraged young adults to tell their health care providers about their supplement use, and to talk to their doctor before starting on a weight loss or energy supplement, especially if they have a history of heart problems.

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