-- health information for the whole family

Herbal Products and Supplements: What You Should Know

This information was developed as part of an educational program made possible by an unrestricted educational grant from McNeil Consumer & Specialty Pharmaceuticals.

Are herbal health products and supplements safe because they’re natural?

Not necessarily. Don’t think that herbal health products and supplements are safer than medicines just because they occur in nature or come from plants. After all, many plants are poisonous! Although herbal products and supplements are advertised as “natural,” they aren’t necessarily natural to the human body.

Unlike prescription and over-the-counter (OTC) medicines, herbal products and supplements don’t have to be tested to prove they work well and are safe before they’re sold. Also, they may not be pure. They might contain other ingredients, such as plant pollen, that could make you sick. Sometimes they contain drugs that aren’t listed on the label, such as steroids or estrogens. Some of these products may even contain toxic (poisonous) substances, such as arsenic, mercury, lead and pesticides.

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What types of herbal products and supplements are available?

Hundreds of herbal products and supplements are available. They are advertised to treat just about any symptom. However, trustworthy evidence usually doesn’t exist to support these advertising claims.

Some of the most popular herbal products and supplements include chondroitin sulfate, echinacea, ephedra (also called ma huang), garlic, ginkgo biloba, ginseng, glucosamine, kava, melatonin, phytoestrogens (such as black cohosh, dong quai and soy), saw palmetto and St. John’s wort.

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Do any health problems increase the danger of taking herbal products and supplements?

Yes. Herbal products and supplements may not be safe if you have certain health problems. You also may be at increased risk of problems from these products if you are elderly. Talk to your doctor before taking herbal products if you have any of the following health problems:

  • Blood clotting problems
  • Cancer
  • Diabetes
  • An enlarged prostate gland
  • Epilepsy
  • Glaucoma
  • Heart disease
  • High blood pressure
  • Immune system problems
  • Psychiatric problems
  • Parkinson’s disease
  • Liver problems
  • Stroke
  • Thyroid problems
If you are going to have surgery, be sure to tell your doctor if you use herbal products. Herbal products can cause problems with surgery, including bleeding and problems with anesthesia. Stop using herbal products at least 2 weeks before surgery, or sooner if your doctor recommends it.

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What are possible side effects of herbal products and supplements?

Many herbal products can cause side effects. Download the PDF file below for some examples of problems that may be caused by herbal products.

PDF File

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Can herbal health products or supplements change the way prescription or OTC drugs work?

Yes. Herbal health products or supplements can affect the way the body processes drugs. When this happens, your medicine may not work the way it should. For example, St. John’s wort reduces the amount of certain drugs absorbed by the body. This may mean the drugs aren’t absorbed at high enough levels to help the conditions for which they are prescribed. This can cause serious problems.

You should be especially cautious about using herbal health products or supplements if you take a drug in one of the following categories:

  • Drugs to treat depression, anxiety or other psychiatric problems
  • Anti-seizure drugs
  • Blood thinners
  • Blood pressure medicine
  • Heart medicine
  • Drugs to treat diabetes
  • Cancer drugs
If you take any of these drugs, talk to your doctor before taking any type of herbal product or supplement.

Download the PDF file below for a list of some of the drugs that may interact with commonly used herbs and supplements. Keep in mind that this table doesn’t list all of the possible drugs that may be affected.

PDF File

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Can herbal health products and supplements cause other problems?

Yes. Herbal products and supplements may have other effects that aren’t listed in the box above. A few examples include the following:

  • Glucosamine products may contain sodium. If you’re on a low-sodium diet, talk to your doctor before taking glucosamine.
  • People who are allergic to shellfish may also be allergic to glucosamine. If you have a shellfish allergy, check with your doctor before taking glucosamine.
  • Don’t drink alcohol if you take kava products. Kava can increase the effects of alcohol.
  • The phytoestrogen black cohosh contains salicylates, so avoid it if you are sensitive to aspirin or other salicylates.
Also, you shouldn’t take more than the recommended dose of any herbal health product or supplement. The problems that these products can cause are much more likely to occur if you take too much or take them for too long.

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Written by editorial staff.

American Academy of Family Physicians

Reviewed/Updated: 12/06
Created: 09/05