t least 23,000 emergency room visits in the United States each year can be traced to dietary supplements, according to the first major study of adverse outcomes from products often marketed as healthy and natural.
More than a quarter of all the ER visits involved young adults — and many of them were taking weight-loss supplements or herbal energy products, according to the study, published Wednesday in the New England Journal of Medicine. More than 20 percent involved young children who took supplements without supervision.
Some of the complaints that drove people to the hospital include: cardiovascular symptoms, such as heart palpitations and chest pain; allergic reactions; choking; and difficulty swallowing because of the large size of some supplement pills. The study was conducted by researchers from the Centers for Disease Control and Prevention.
The huge — and hugely popular — dietary supplement industry is largely unregulated. Previous studies have identified dangerous levels of certain ingredients in some supplements, including a chemical similar to the stimulant amphetamine.
But this is the first study to look systematically at side effects. The researchers reviewed nearly a decade of ER visits, covering 2004 to 2013.
“This study is the most important research that’s been published on supplements in the last 20 years,” said Dr. Pieter Cohen, a physician at Harvard Medical School who studies dietary supplements and wasn’t involved in the research.
“Now that we have the data, it should be a game-changer,” Cohen said, calling on the Food and Drug Administration and Congress to step up regulation of dietary supplements. “The belief is that they’re entirely safe, but now the science says that they’re not.”
Dr. Andrew Geller of the CDC, who wrote the study, said it’s likely that the study significantly underestimates the number of adverse events caused by dietary supplements.
The study didn’t track patient visits to military hospitals, doctor’s offices, or urgent care clinics. It didn’t look at adverse events tied to dietary supplements in beverage form, such as energy drinks and herbal teas. And it didn’t look at deaths.
The supplement industry dismissed the study as insignificant, noting that many consumer products can cause injuries.
“Things are going to happen,’’ said Duffy MacKay, who heads scientific and regulatory affairs at the Council for Responsible Nutrition, a trade association for the supplement industry.
The group estimates that 150 million people in the United States take supplements, including children’s vitamins.
MacKay said the industry takes consumer safety seriously and recommends that people consult their doctors and follow instructions on the supplement packages. He also noted that a 2006 law requires manufacturers to report adverse effects of supplement use to the FDA.
“Over this 10-year period, a lot has changed to make these products more safe,” he said.
Dietary supplements include vitamins, weight-loss aids, herbal supplements, and similar products. Unlike pharmaceutical companies, supplement makers are not allowed to claim that their products cure or treat a particular condition, but can make general claims that they promote health and nutrition.
They are sold in supermarkets, pharmacies, and specialty supplement stories without prescriptions.
The FDA, under the Dietary Supplement Health and Education Act of 1994, is barred from reviewing dietary supplements for safety before they hit the market. The agency can intervene only when supplements are flagged as possibly dangerous, but the FDA said even that step can be difficult.
“The agency faces the challenge of having limited resources to monitor the marketplace for potentially harmful dietary supplements,” said Lyndsay Meyer, the FDA’s dietary supplement representative.
The FDA’s hands-off approach extends to the packaging of dietary supplements. The study found that many of the injuries to young children occurred because they got their hands on pills that were not stored in childproof containers.
The study called for “innovative safety packaging and targeted education” to reduce the risk to children.
A bill pending on Beacon Hill would make Massachusetts the first state to ban the sale of dietary supplements marketed for weight loss and muscle-building to children under 18. The bill would also require retailers to move the products from open shelves to behind the counter.
It has been tough to study dangerous side effects of supplements in the past because many people don’t share their supplement regimens with medical professionals — and medical professionals don’t often think to ask, experts said.
As a result, it can be difficult for doctors to tie specific symptoms to a patient’s use of dietary supplements.
“People may not realize that dietary supplements can cause any adverse effects,” Geller said. “While some may have benefits, the risks aren’t the same from supplement to supplement,” he added.