Supplements are largely unregulated, so there’s no real way to know what you’re buying, and whether it is safe. Supplements are not tested by the U.S. Food & Drug Administration (FDA). Many are manufactured in unregulated plants overseas.
Our bodies process substances differently as we grow older. It may take longer for the ingredients in supplements to be eliminated from our body, which can allow a toxic dosage to accumulate.
Supplements may interact harmfully with prescription drugs. The National Institutes of Health (NIH) gives some examples of interactions to avoid:
- Supplements may increase the effect of a prescription drug. Certain herbs, such as goldenseal and schisandra, may slow down processes in your body that change drugs into inactive substances. So if you take this herb, other drugs you are taking may build up in your body and the effects may be too strong.
- Some supplements make prescription drugs less effective. They speed up processes in the body that change drugs into inactive substances. For example, the NIH reports that St. John’s wort may decrease the effectiveness of more than 70% of all drugs.
- Some supplements can have a bad interaction with prescription medications. St. John’s wort and a number of other herbal products can alter the effects of prescription drugs for depression, as well as medication prescribed for diabetes, cholesterol, anxiety, angina, seizures, digestive disorders, cancer and HIV.
- Supplements can interact with nonprescription drugs, as well. For example, green tea supplements can interact with the decongestant pseudoephedrine. And some herbs increase the risk of bleeding associated with taking aspirin.
- Supplements can be especially dangerous when taking drugs with a “narrow therapeutic range.” These drugs are only safe and effective at a very specific level, and include medications for heart problems, seizure disorders, and prevention of rejection in organ transplant.
- Dietary supplements may cause problems during surgery. They may affect response to anesthesia or increase the risk of bleeding.
Tell all your health care providers—your doctor, your dentist and any specialists you see—about all the supplements you take. They can help you avoid harmful interactions. If you see a complementary practitioner, such as a naturopath, they should know, as well.
Even better, talk to your doctor before you decide to take supplements. Your doctor can counsel you on which supplements would benefit you, and which would be useless or even dangerous.
The information in this article is not intended to replace the advice of your health care provider. Talk to your doctor about all the medications and other substances you take.