Dietary Supplements: What Is Safe?

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FDA regulation of drugs versus dietary supplements

All prescription and non-prescription drugs are regulated in the United States by the Food and Drug Administration (FDA). But dietary supplements are treated more like special foods.

Because supplements aren’t considered drugs, they aren’t put through the same strict safety and effectiveness requirements that drugs are. So all the drugs you can buy, even without a prescription, must be proven safe and effective – but dietary supplements do not.

Drugs are considered unsafe until proven safe

In general, the FDA considers new drugs to be unsafe until they are proven safe through clinical trials. And the FDA must approve any new drug before it can be legally sold in the US. Clinical trials are studies done under well-controlled conditions on human volunteers. These tests must be done on all drugs – even those that are sold over the counter (without a prescription). The FDA approval process requires that the drug be proven in a series of clinical trials. These studies must show “substantial evidence” that the drug is both safe and effective for each of its intended uses. (See our document Clinical Trials: What You Need to Know for more on this process.)

Once the FDA approves the drug, it must be manufactured under carefully monitored conditions and packaged with complete information on the best dose, route, and schedule. The package information must also include:

  • Conditions the drug has been proven to treat
  • Known side effects
  • Contraindications (special conditions under which using the drug should not be used because it would cause too much risk)
  • Unsafe interactions with other drugs

Once the general public is using a new drug, the FDA follows up on any ill effects patients and their doctors report (see “How to report adverse reactions” in the section “Guidelines for choosing dietary supplements safely”). The drug company is required to file information they get about side effects as well. This data helps ensure that any side effects not seen in the clinical trials will eventually be found and tracked for the safety of other people.

While counterfeit medicines are sometimes made and circulated, they don’t usually get into wide circulation unless they’re being distributed outside of the usual channels (such as from undocumented internet pharmacies). This is because drugs are typically seen by doctors, pharmacists, and nurses. When counterfeit drugs do make it into the system, health professionals often notice the differences in response between the real and fake drugs so that they are caught quickly. The FDA takes quick action when these problems are found.

Dietary supplements are considered safe until proven unsafe

In 1994, the Dietary Supplement Health and Education Act (DSHEA) defined dietary supplements as a category of food, which put them under different regulations than drugs. They are considered safe until proven otherwise. The DSHEA says that dietary supplements cannot contain anything that may have “a significant or unreasonable risk of illness or injury” when the supplement is used as directed on the label, or with normal use if there are no directions on the label.

A dietary supplement is considered “new” if it contains an ingredient not recognized as a food substance, unless it was sold as a supplement before October 1994. If it is new, the manufacturer must provide the FDA with reasonable evidence that the new ingredient is safe before the supplement is marketed to the public.

But manufacturers are not required to test new ingredients or supplements in clinical trials, which would help find risks and potential interactions with drugs or other substances. The DSHEA gives the FDA permission to stop a company from making a dietary supplement, but only when the FDA proves that the product poses a significant risk to the health of Americans. This means they are found unsafe only after they cause harm. This is the reverse of the way prescription and non-prescription drugs are handled.

Dietary supplements are usually self-prescribed, so there’s no controlled system for reporting bad reactions and side effects. Doctors and patients can report problems, but are not required to do so. If a supplement has unknown side effects or interactions with other drugs, foods, or supplements, they are not likely to be discovered as quickly as those of new drugs on the market.

What kinds of problems have there been with supplements and herbs?

Many dietary supplements have clean safety histories. For instance, millions of people take multi-vitamins safely and have no ill effects. Many manufacturers are very careful with their claims, labeling, and the ingredients they use in their products.

But since they became widely available in 1994, the FDA and some independent researchers have found problems with some dietary supplements. Products like herbs were sometimes tainted with germs, pesticides, or toxic heavy metals. Other supplements did not contain what was listed on the label. Still others contained more or less than the amount listed on the label.

This problem extends beyond the supplement makers and sellers. Some herbal suppliers (those who grow, harvest, or sell the crops) may mix or even substitute their crops with less expensive or more readily available plants. There’s also the problem of accidental contamination, when one plant grows in with others, as well as cases of mistaken identity (when one plant looks like another). Given the global market, all of these problems can make it harder for a company to be sure that what they thought they were buying to make supplements is actually the herb they wanted.

In 2013 researchers in Toronto published a report in which they sampled and analyzed 44 herbal supplements. The supplements were sold in both the US and Canada, and labeled as containing single herbs. Using DNA bar coding analysis, less than half the supplements (48%) contained any of the herb listed on the label. More than half of the supplements contained something that wasn’t on the label (substitutions or fillers). Even among the samples that contained the herb on the label, many also contained fillers or contaminants.

A more recent trend is extra ingredients in supplements. Some “herbal” supplements have been found to contain prescription drugs or other compounds that are not listed on their labels. For example, some supplement ads are targeted to men as “enhancers” or muscle builders. Certain of these so-called “supplements” have been found to contain substances much like Viagra® or Cialis®, and have been recalled. “Prostate health” supplements have been found to contain terazosin, a prescription drug used to treat the symptoms of an enlarged prostate. Other ads target women and tout the supplement as an aid to weight loss. Some of these “weight loss supplements” contained the weight loss drug sibutramine, which was banned in the United States because of the risk of heart attack and stroke. The supplement makers recall these only after they have been found to have these illegal additives. Then the FDA can seize these drugs and prosecute the companies who make them.

There are also times that new ingredients with little-known effects are slipped into supplements. In one situation, supplements were labeled as being made from geranium but turned out to contain the stimulant drug dimethylamylamine (DMAA). This type of supplement was sold as a “natural stimulant,” but it contained DMAA, a man-made drug. The DMAA-containing supplements were exposed after some serious events, including several deaths, leading the FDA to send warning letters to US manufacturers in 2013.

These kinds of extras can cause serious health issues for people who take the supplement. There are also risks of mystery drug interactions because the person doesn’t know that he or she is taking a drug.

Despite all these issues, the FDA is not legally responsible for the safety of dietary supplements; the manufacturers are. The manufacturers are also responsible for what’s in them, and being sure the contents are the same from one pill or package to another. The FDA only looks into reported problems or safety hazards. To find out more about what’s in a supplement, the manufacturer is your first contact.

To avoid tainted supplements, don’t buy any of these:

  • Products that claim to work like prescription drugs
  • Products that are advertised through mass e-mails
  • Products marketed mainly in a foreign language
  • Products that promise weight loss, body-building, or enhanced sexual performance
  • Products that say they are a legal alternative to anabolic steroids

Last Medical Review: 11/22/2013
Last Revised: 06/02/2014