Are dietary supplements safe?

The problem with dietary supplements is that they’re not all regulated by the FDA, so you don’t know if ingredients have been left off the product label. We can’t just generally say, yes, all dietary supplements are safe. Some of them are, some of them are not. But we’re not talking about multivitamins. Multivitamins or minerals are safe.
Dariush Mozaffarian, MD
Internal Medicine
Dietary supplements may legally contain vitamins, minerals, herbs, amino acids, enzymes, organ tissues, and a few other substances -- in short, practically any ingredient promoted as a way to bolster your diet and, presumably, your health. The Food and Drug Administration (FDA) does not certify supplements for safety or effectiveness the way it monitors drugs. Under the Dietary Supplement Health and Education Act of 1994, the FDA cannot approve supplements or demand that manufacturers undertake rigorous studies to prove their worth. The FDA doesn't set potency or dosage standards, either. Manufacturers are left to police themselves. And before a worrisome supplement can be pulled off the market, the FDA has to prove that it creates a significant health risk.

This can be a problem, as is made clear by a ConsumerLab report. The consumer watchdog organization tested the quality and contents of 29 of the leading multivitamin and multimineral products for adults and children sold in the United States and Canada. Eight products did not meet claims stated on their labels or had other quality issues, while another 12 provided levels that may be too high for healthy people. For example, one men's multivitamin supplement contained just over 2,000 mcg of folic acid, which is twice the safe upper limit for that vitamin.

While supplement manufacturers can't legally claim to prevent, treat, or cure specific diseases, they can make statements that sound pretty close. They are allowed to make "structure-function" claims that sound impressive to most consumers. A product may "build strong teeth" or "improve memory" or "boost the immune system." Manufacturers can make these assertions without supplying a stitch of proof to any agency. Your cue for healthy skepticism should be the words printed alongside: "This statement has not been evaluated by the Food and Drug Administration."

Certain health claims backed by substantial scientific agreement and not limited to particular brands can appear on supplement bottles. For example, supplement manufacturers can advertise that "Calcium helps protect against osteoporosis" and "Folic acid may prevent neural tube defects in fetuses" because these statements are borne out by science and have been carefully evaluated.

In short, it is difficult to be sure if a dietary supplement is safe.
Dietary supplements may not be risk-free under certain circumstances. Be sure to consult your health practitioner before purchasing or taking any supplement if you are pregnant, nursing a baby, or have a chronic medical condition such as diabetes, hypertension, or heart disease. Also, while vitamin and mineral supplements are generally considered safe for children, you may wish to check with your doctor before giving these or any other dietary supplements to your child.

In many cases dietary supplements and homeopathic remedies can be marketed without providing evidence of safety or efficacy. In order for a product to get removed from the shelves in the United States, for example, the FDA must prove that it is dangerous -- and that is often to the detriment of the consumer.

Supplement manufacturers are allowed to make claims regarding health, nutritional content, and structure/function, subject only to limited restrictions. 

Health claims describe a relationship between a dietary supplement ingredient and reducing the risk of a disease or health-related condition. For example, the label on a bottle of Evening Primrose Oil capsules might claim that the product, "Provides relief from symptoms associated with PMS and menopause such as cramps, hot flashes, breast tenderness, and moodiness."

Nutrient content claims refer to the percentage of DV (daily value) of the nutrient the supplement provides.

structure/function claim is a statement describing how a product may affect the organs or systems of the body. It can't mention a specific disease. For example: "COQ10 supports heart function as a component of the electron transport system, and as an antioxidant protects mitochondrial membranes and cholesterol from oxidation."

When selecting a nutritional, dietary, or herbal supplement, keep in mind the following:
  • Nutritional, dietary, and herbal supplement manufactures are not are required to run studies to determine product safety or efficacy.
  • In the U.S., the FDA does not analyze the contents of dietary supplements.
  • Dietary supplement manufacturers in the U.S. must meet the FDA’s Good Manufacturing Practices (GMP) for food, but some companies also follow the GMP for drugs on a voluntary basis.
  • Daily Value (DV) describes the recommended daily intake of a particular nutritional supplement, if one is established.
Marjorie Nolan Cohn
Nutrition & Dietetics
A dietary supplement can be anything from vitamins, minerals, or herbs to botanicals, amino acids, and other substances like organ tissues or metabolites. You find them in many forms such as tablets, capsules, soft gels, gelcaps, liquids, or powders. Whatever their form, dietary supplements are not considered food, and all of them must be labeled as “dietary supplements.”

Congress defined the term “dietary supplement” in the Dietary Supplement Health and Education Act (DSHEA) of 1994. Under DSHEA, the supplement company is responsible for determining that the dietary supplements it manufactures and distributes are safe and that any representations or claims made about them are substantiated by adequate evidence to show that the claims are not false or misleading. Only after a supplement has been reported to cause adverse health effects does the FDA perform an investigation.

Dietary supplements are not regulated by the Food and Drug Administration (FDA) in the same way that prescription medications are. Instead the safety of each and every supplement is determined by the company that makes and sells it. That means that you should never take a supplement without doing research, getting a recommendation from your dietitian, and checking in with your physician.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.