A number of supplements may interact in harmful ways with prescription or over-the-counter drugs. For example, St. John's wort may alter the breakdown of many drugs including antidepressants and birth control pills. Vitamin K, ginkgo biloba, garlic, and vitamin E may interact with blood-thinners.  That's why it's essential that you consult your physician before starting a supplement regimen or making changes to your treatment regimen or prescribed medications. 
Men who choose to drink and can do so responsibly may benefit from one to two drinks a day, counting 5 ounces of wine, 12 ounces of beer, or 1.5 ounces of spirits as one drink. But women face an extra risk: Even low doses of alcohol can raise their risk of breast cancer. So women who choose to drink might be wise to limit themselves to half as much as men.
Learn. Find out as much as you can about any dietary supplement you might take. Talk with your doctor, your pharmacist, or a registered dietitian. A supplement that seemed to help your neighbor might not work for you. If you are reading fact sheets or checking websites, be aware of the source of the information. Could the writer or group profit from the sale of a particular supplement? Read more about choosing reliable health information websites.
Dietary supplements are complex products. The FDA has established good manufacturing practices (GMPs) for dietary supplements to help ensure their identity, purity, strength, and composition. These GMPs are designed to prevent the inclusion of the wrong ingredient, the addition of too much or too little of an ingredient, the possibility of contamination, and the improper packaging and labeling of a product. The FDA periodically inspects facilities that manufacture dietary supplements.
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