Knee acting up? Swallow some glucosamine. Brain a little foggy? Pop some omega-3. Worried about the flu? Reach for Echinacea, or ginseng or zinc—or all three.
You’ve likely heard recommendations like these, since the market for health supplements from vitamin D to ginkgo biloba has exploded in recent decades. Sales of supplements topped $27 billion in the U.S. last year and are expected to reach nearly $300 billion worldwide by 2024. Whether you’re suffering through an ailment or hoping to prevent one, there’s undoubtedly a pill, powder or probiotic that boasts the power to mend or defend your body.
But if you think picking up an over-the-counter supplement is a risk-free proposition, you’re mistaken, says Dr. Mark Moyad, director of complementary and alternative medicine at the University of Michigan Medical Center. “The biggest problem I see is that consumers treat these [supplements] differently than they do prescription drugs, and they shouldn’t,” Moyad says. “Like drugs, supplements come with benefits and limitations, and like drugs there are serious risks involved.”
What sorts of risks? “We know that taking too much of certain vitamins can encourage tumor growth and cancer,” Moyad explains. Supplement contamination is another major issue, says Dr. JoAnn Manson, chief of the division of preventative medicine at Boston’s Brigham and Women’s Hospital.
Manson says lead, cadmium and other metals have turned up again and again in supplements. “Some of these metals have been linked to cognitive problems, heart disease and cancer,” she says. That’s to say nothing of more urgent supplement-related health issues, like the irregular heartbeats or chest pains that send an estimated 23,000 people to the emergency room each year, according to a study. “Supplement products for weight loss or increased energy were commonly involved in these visits,” says Dr. Andrew Geller, a CDC medical officer and first author of that study.
Supplement ingredients may also “interact or detract” from common prescription medications, Manson says. Ginseng, for example, can reduce the effectiveness of blood clotting drugs, according to University of Chicago researchers. But a 2013 Consumer Reports survey found a majority of people taking supplements don’t check with their pharmacist about potentially risky interactions.
All of this may come as a shock to those who assume anything natural and sold over-the-counter is harmless. But Manson says this assumption is misguided. “Cyanide, arsenic and tobacco are all natural and are also toxic,” she points out.
Earlier this year, she coauthored a global review of dietary supplements and their health impacts. While nutrients like iron and vitamin A undoubtedly help malnourished people in many developing countries, the evidence that healthy American adults benefit from supplements is much spottier, she says.
“The vast majority of supplements on the market today are not thoroughly tested for safety or efficacy,” she explains. Take one or several of them, and there’s the potential for “almost anything” to happen, she adds.
“I call it being a clinical trial of one,” Moyad says of many consumers’ willingness to self-prescribe a cocktail of different dietary supplements. The companies that make and market these products are also part of the problem, he adds. “When you look at the research, you might find good evidence that a single active ingredient can treat a specific condition,” he explains. “But then you go to the store and look at the back of your melatonin or whatever, and you see that one active ingredient along with six others.”
He says supplement manufacturers pack their pills with extra vitamins or herbs or nutrients so that they can raise the price or differentiate their products from all of the other supplements on the shelf. “But we have no idea what happens when you mix all those active ingredients together,” he says.
If you assumed some regulatory agency was monitoring the safety of supplements, you’re right. But that agency—the U.S. Food and Drug Administration (FDA)—doesn’t treat diet and health supplements the way it treats prescription drugs, or even OTC medications like aspirin. Instead, diet and health supplements are regulated more like food products. That is, the FDA steps in when they receive reports of injury or illness resulting from a supplement. They also conduct surveys, product tests and label reviews, and engage in other monitoring practices to help ensure unsafe products are weeded out, says Lyndsay Meyer, a spokesperson for the FDA.
But most of what the FDA does is reactive—pulling unsafe products off the shelves—rather than ensuring the products are safe before they hit the market. “We have a regulatory framework that limits our authority,” Meyer says. “The [existing] law does not allow for supplements to be regulated like drugs or OTC medications.”
Manson says that’s a problem. “I absolutely think there should be increased regulatory oversight, and supplement makers should have to show that their products are safe,” she says.
Does this mean you should dump all your supplements? Not necessarily. Manson says there are many evidence-backed reasons to take health supplements. One example: Some prescription medications can mess with your body’s ability to absorb certain nutrients, and a supplement can help fill those shortfalls. “Women of child-bearing age, especially during pregnancy or before, should take additional folic acid to prevent neural tube defects [in their newborns],” Manson adds.
But as a general rule of thumb, “unless your physician has told you that you have a nutritional deficiency, or higher requirements than usual, it’s advisable not to take supplements,” she says.
Moyad says he partly agrees, but is sympathetic to patients who might not have easy access to a doctor’s guidance. He says supplements can be very beneficial, but you have to do your homework about the proper dosage and the potential side effects.
The National Institutes of Health has a comprehensive database with information on supplement side effects and risks. Moyad also recommends talking with your pharmacist about potential interactions, and checking for approval seals from reputable third-party product testers like NSF or U.S. Pharmacopeia (USP).
“Less is more” is a good adage to follow when it comes to supplements, Moyad adds. “Diet and exercise should always be your first paths taken,” he says, “and if those don’t work, you need to educate yourself about the products you’re considering.”