In 1994, federal legislation—the Dietary Supplement Health and Education Act (DSHEA), passed after intensive lobbying by the supplements industry—essentially removed dietary supplements from most regulation by the FDA. Dietary supplements, according to this law, are to be regulated as a class of foods, not drugs. All else follows from this: That supplements need not be screened for safety and effectiveness before they are marketed, for example, and that it is the responsibility of the FDA to prove that supplements are harmful.

Under DSHEA, manufacturers must notify the FDA at least 75 days before marketing a supplement that contains a new dietary ingredient (one that was not marketed in the U.S. before 1994). Supplements containing a new ingredient that has not been submitted to the FDA are considered adulterated. The FDA estimates that more than 5,000 new dietary supplement products come on the market each year, but that it has received fewer than 1,000 notifications since DSHEA was passed in 1994. That shows one of the many holes in the system—holes the FDA is attempting to plug.

In addition, DSHEA limits the claims made on supplements’ labels and on the Internet (even in testimonials and website links). With only a few exceptions, they cannot assert that the supplements treat or cure disease. They may make only “structure/function” or “health maintenance” claims. Here are some examples:

• A label can say “helps improve your mood” but not “reduces depression.”

• It can say “maintains a healthy circulatory system” but not “prevents cardiovascular disease.”

• It can say “maintains cholesterol in a healthy range” but not “lowers cholesterol.”

• It can say “supports the immune system” but not “prevents colds and flu.”

For years, the FDA has attempted to make a distinction between “disease claims” (also called “medical claims”), which it strictly limits, and “structure/ function claims” or “health maintenance claims,” which are largely unregulated. It is nearly impossible for consumers to tell the difference between reasonable, permitted claims and the overblown ones—or to spot deceptive advertising. The fine line between a disease claim and a structure/function claim is hard for even the experts to define.

Disease claims. These focus on preventing, treating, curing, or diagnosing a disease or its signs or symptoms. Some examples: “prevents osteoporosis,” “protective against cancer,” “lowers cholesterol,” “reduces the pain and stiffness of arthritis,” “alleviates constipation,” and “improves urine flow in men.” Such claims require prior FDA review for efficacy, including “significant scientific agreement.” Among the few explicit health claims that have met the FDA’s high standards of proof are the claims that calcium helps prevent  osteoporosis and that folic acid (a B vitamin) helps prevent birth defects.

Even “implied” disease claims require FDA approval, though this is where things get really murky. Such claims would include “prevents bone frailty,” “promotes urinary tract health,” “improves joint mobility,” and “helps maintain intestinal microflora.” Supplement  manufacturers, denying that these are medical/disease claims, often push to see how far they can go with such implied claims.

“Health maintenance” or “structure/function” claims. These include claims such as “maintains a healthy circulatory system” as well as claims about common conditions associated with “life stages,” such as aging, menopause, or pregnancy. Other nondisease claims include “arouses sexual desire,” “boosts stamina,” and “enhances muscle tone.” None of these vague claims need FDA approval, but there must be a disclaimer on the label saying that the statement has not been evaluated by the FDA and that the product is not intended to diagnose, treat, cure, or prevent disease. Of course, this disclaimer is usually in tiny type.

Qualified health claims. In 2004, bowing to pressure from industry via freedom-of-speech court cases, the FDA started allowing more questionable, “qualified” health claims, which are hedged with qualifiers and based on “very limited,” “preliminary,” and possibly even poor-quality evidence. Because of all the qualifiers, supplement makers rarely put such claims on labels. Though the industry pushed for the right to use qualified health claims, some supplement makers have challenged the restrictive wording demanded by the FDA by taking the agency to court and arguing that their freedom of speech is being limited.

In recent years, the FDA has issued a record number of warning letters to marketers about illegal disease claims made on supplement labels, in ads, and on the Internet. An investigation by the Inspector General of the Department of Health and Human Services concluded that many supplement companies make unsubstantiated health claims on their labels and do not comply with federal law in other ways. The report recommended that the FDA be given greater authority in order to crack down on such illegal claims.

What About the Risks?

Though they are almost never listed on labels or mentioned on websites, the risks include the following:

• Supplements can have serious and even fatal side effects. They lead to an average of 23,000 visits to U.S. emergency rooms and more than 2,100 hospitalizations each year, according to a decade-long federal study in the New England Journal of Medicine in 2015. Nearly 30 percent of the visits involve young adults (20 to 34), and 20 percent unsupervised children. Supplements marketed for weight loss and energy boosting were found to be the most common culprits, often causing cardiac symptoms such as palpitations, chest pain, and fast heartbeat. Allergic reactions, headaches, dizziness, vomiting, and abdominal pain were also commonly reported.

• In particular, many supplements can be toxic to the liver, especially when taken long term or in high doses, according to 2014 guidelines from the American College of Gastroenterology as well as a 2016 review article (see page 22). Herbal products that can harm the liver include chaparral, comfrey, kava, skullcap, and even green tea extract. In some cases, impurities or toxins are introduced during processing of the product.

• Some supplements have the same adverse effects as prescription drugs. For example, red yeast rice extracts that claim to lower cholesterol actually contain a statin drug (see page 26). Other supplements illegally contain hidden pharmaceutical ingredients. Thus, supplements that claim to “cure” impotence may actually contain the drug sildenafil (brand name Viagra), along with other potentially dangerous adulterants. But while the drugs require a doctor’s supervision (and precautionary labeling), people generally take supplements on their own, so there’s no one to check for side effects.

• People who self-medicate with supplements may be missing out on treatments or dietary measures that could really help them.

• Dietary supplements can interact with both prescription and nonprescription medications, making the drugs less or more potent.