Supplement and vitamin use remains popular. Here’s how to choose wisely.

Americans spend billions of dollars every year on dietary supplements that claim to promote almost every aspect of our health. But how much do you know about the supplements you’re taking?

A recent government study found that nearly 60 percent of adults take vitamins, minerals, fish oil, herbal capsules, melatonin, probiotics and other types of dietary supplements. While most people used just one or two supplements — multivitamins and vitamin D were the two most popular products — it was not uncommon for people to report using three, four or more supplements at a time.

Among some parts of the population, it’s not unusual to down a handful of vitamins or supplements every day. About 15 percent of adults said they used four or more dietary supplements. Among older adults, the number reporting multi-supplement use is even higher — about 25 percent of adults 60 or older use four or more. About 35 percent of children and adolescents used dietary supplements, and nearly 10 percent of children between 2 and 5 years old were given two or more dietary supplements.

Experts say that vitamin and mineral supplements are generally safe when taken in small to moderate doses, like the amounts found in a basic multivitamin. Dietary supplements can be beneficial for pregnant women and for people with nutrient deficiencies and other health conditions. A clinical trial earlier this year found that for people who are 60 and older, taking a daily multivitamin helped to slow memory loss. Other studies have found that probiotic supplements can help with gastrointestinal disorders such as irritable bowel syndrome.

But taking supplements comes with risks, and for many healthy adults, it’s not always clear from research that the benefits outweigh the risks.

In fact, some randomized trials have found that assigning people to take supplements with large doses of beta-carotene, selenium, and vitamins A, C, and E actually increased mortality rates. Rigorous clinical trials have also failed to support the hype around vitamin D, finding that people who were assigned to take the popular supplement did not develop lower rates of cardiovascular disease, cancer or bone fractures despite widespread marketing claims to the contrary.

Supplements don’t follow the same rules as drugs

Many people assume that the Food and Drug Administration tests supplements for safety. But that’s not how it works.

“Dietary supplements enter the market before there’s any real review of them by the FDA,” said Amy B. Cadwallader, the director of regulatory and public policy development at the United States Pharmacopeia, a nonprofit organization that examines the quality of drugs, food and dietary supplements.

Under federal law, companies are allowed to operate on the honor system. The FDA’s role in regulating supplements mostly involves trying to make sure products are safe and accurately labeled after they have already entered the marketplace.

Are you getting what you paid for?

In the United States, companies sell an estimated 90,000 dietary supplements, representing a roughly $50 billion industry. As a result, some experts say, consumers who buy supplements can’t always be sure that they are getting what they paid for. Studies of melatonin, fish oil, probiotics, ginkgo biloba, and other supplements have found that the doses and compounds listed on their labels are often not what are found in their bottles.

  • In one study in the journal Pediatric Research, researchers tested 16 probiotic supplements and found that only one of them contained the specific bacterial strains listed on its label.
  • In another study, researchers tested 30 dietary supplements that claimed to strengthen immune health and found that 17 of the products were “misbranded.” These supplements either lacked key ingredients listed on their labels — such as vitamin B12, garlic extract, ginger root and folate — or they contained a variety of unlisted ingredients.
  • One study by the FDA estimated that the agency is notified of less than 1 percent of all adverse events linked to supplement use. Another study by the federal government estimated that injuries caused by supplements are responsible for about 23,000 emergency room visits each year.

Howard Luks, an orthopedic surgeon and sports medicine specialist in New York, said he routinely encounters patients who worry about potential side effects from medications but have no problem taking 10 or 20 supplements that they heard about from health influencers on social media. He said that many people who lost trust in public health authorities during the pandemic have turned to social media influencers for health advice.

“They view supplements as being holistic, natural, and therefore not potentially harmful for them,” he said.

In one case study published in March, doctors in New Jersey described a 76-year-old woman who went to an emergency room after experiencing heart palpitations, dizziness and fainting episodes. It turned out she had been taking black cohosh, an herbal supplement often used to treat hot flashes. A few days after stopping the supplement, her heartbeat returned to normal, and her other symptoms disappeared.

In another recent case, a 47-year-old woman in Houston suffered jaundice and liver damage after taking a supplement containing a blend of probiotics and herbal extracts. The case report noted that dietary supplements account for about 20 percent of drug-induced liver injuries nationwide.

How to shop smarter for supplements

Here are some tips when buying supplements.

Look for third-party certifications: The United States Pharmacopeia, or USP, vets dietary supplements to ensure they are meeting high standards for factors such as purity and potency. USP has a voluntary program through which companies can have their supplements and facilities routinely tested and examined. Companies that meet the organizations high standards are allowed to use a black and yellow “USP Verified” logo on their products. You can find them using the product-finder search tool on USP’s website. NSF is another independent group that tests and reviews dietary supplements. You can look for the blue and white “NSF” logo on your supplements or go to the group’s website to look up products.

Do your homework. Consumerlab.com is an independent laboratory that tests dietary supplements to see if they contain the ingredients and doses listed on their labels. The company publishes reports with their findings on a wide variety of supplements, which you can access on their website for a fee.

Talk to your doctor or pharmacist. Many people don’t realize that a lot of supplements and medications use the same metabolic pathways and that they can cause dangerous side effects when you combine them, said Michael Schuh, an assistant professor of pharmacy, family medicine and palliative medicine at the Mayo Clinic in Florida.

Vitamins E and K, ginseng, ginkgo biloba, resveratrol, turmeric and CoQ10 for example can interact with blood thinning medications. Vitamin C can interact with statins, niacin, estrogen, warfarin and chemotherapy drugs. St. John’s wort can make antidepressants and birth control pills less effective.

“We see it with a lot of supplements,” Schuh said. “Even something like resveratrol from grape skins: When you take it in concentrated form, it can interact with a lot of medications.”

Do you have a question about healthy eating? Email EatingLab@washpost.com and we may answer your question in a future column.

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