More than half of all Americans report using dietary supplements, including vitamins D and E…minerals like calcium and magnesium…herbs such as echinacea and garlic…and special-purpose supplements such as glucosamine, probiotics and fish oil.

What few people realize is the extent to which certain dietary supplements can interact with prescription or over-the-counter (OTC) drugs.

Do you know which supplements are potentially harmful? Take this quiz to find out…

Taking a dietary supplement with a drug may _____ the drug’s effects.

When taking certain medications and supplements together, the potency of the drug can be increased and unwanted side effects may result. For example, the blood-thinning effect of warfarin (Coumadin) can be increased by such supplements as ginkgo biloba and vitamin E, possibly leading to internal bleeding or stroke. On the other hand, some supplements can decrease a drug’s effectiveness. For example, vitamin K interferes with the blood-thinning effect of warfarin. This means you don’t get the full benefit from the drug if you take supplemental vitamin K.

More than 70 % of all prescription medications have been reported to interact with this botanical supplement.

St. John’s wort is used as a natural remedy for depression, anxiety and sleep disorders. With more than 2,000 peer-reviewed articles published on its safety and efficacy, St. John's wort is the most studied botanical dietary supplement in the world. It also has the distinction of being one of the most problematic dietary supplements with regard to drug interactions. Many antidepressants, antihistamines and sedatives are among the numerous drugs that are known to interact with St. John’s wort.

Unlike prescription drugs, all OTC drugs are safe to combine with supplements.

Most people know that there are potential interactions between prescription drugs and supplements, but some drugs that are available without a prescription can interact with supplements, too. When the aspirin in your medicine cabinet, for example, is combined with the herbal supplement ginkgo biloba, severe bleeding, including intracranial bleeding, can occur. On the flip side, zinc reduces the absorption of ibuprofen (Motrin, Advil) and naproxen (Naprosyn, Aleve), making them less effective.

Advertisement

Many people use the supplement _____ as a natural sleep aid, but it may be dangerous when combined with other supplements or medications.

Taking melatonin with sedative drugs (such as benzodiazepines, narcotics and some antidepressants) or certain other supplements that have sedative properties (such as valerian) may cause too much sleepiness. When taking these combinations, it can be dangerous to engage in activities that require alertness, such as driving. In addition, melatonin may slow blood clotting, so taking it with anticoagulant medications, such as heparin or warfarin, may increase your chances of bruising and bleeding.

This tasty treat may further increase the risk of bleeding when consumed with certain supplements or drugs.

Sorry, Easter Bunny, but it’s true—chocolate may increase the risk of bleeding when consumed with supplements such as ginkgo biloba and garlic that can also increase bleeding risk. Chocolate can also increase bleeding risk when consumed with such drugs as aspirin, blood thinners, antiplatelet drugs such as clopidogrel (Plavix) and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin, Advil) or naproxen (Naprosyn, Aleve). If you eat chocolate and have a bleeding disorder or take any drugs or supplements that may increase the risk of bleeding, discuss this with your doctor. Dosing adjustments may be necessary—or you may need to give up chocolate!

If you don’t eat a variety of nutritious foods, a multivitamin will provide adequate amounts of essential nutrients.

This is true, but it’s important to understand that supplements can’t take the place of the variety of foods that are important to a healthful diet. Also, keep in mind that some ingredients found in dietary supplements, including multivitamins, are already added to a number of foods—for example, many vitamins and minerals, such as vitamin D, folic acid, iron and calcium, are found in fortified breakfast cereals, juices and milk. As a result, you may be getting higher amounts of these vitamins than you think. At the very least, getting more vitamins and minerals than you need is expensive—and it can raise your risk of experiencing side effects based on your total intake from the supplement and your diet.

Advertisement

Which governmental agency oversees the regulation of dietary supplements in the US?

The Food and Drug Administration (FDA) oversees the regulation of dietary supplements but under a different set of regulations than those that apply to foods and drugs (prescription and OTC). Under the Dietary Supplement Health and Education Act of 1994, the dietary supplement manufacturer is responsible for ensuring that a dietary supplement is safe before it is marketed. After the product reaches the market, the FDA is responsible for taking action against any unsafe dietary supplement. Manufacturers must also ensure that product label information is truthful and not misleading. Unlike the requirements for drugs, the manufacturer of a dietary supplement does not have to prove that the supplement is effective—but can state that a product addresses a nutrient deficiency, supports health or reduces the risk of developing a health problem, if that is true.

For more information on dietary supplements: The Drugs and Supplements section of the MedlinePlus Databasethe National Institutes of Health’s Fact Sheets on Dietary Supplements…and PubMed’s Dietary Supplements Subset are excellent resources. Even though the benefits of certain dietary supplements, including some vitamins and minerals, have been well established by scientific evidence, some other supplements need further study. Be sure to discuss the use of any supplements with your health-care provider and pharmacist. To find more information online, check the organizations mentioned above.