According to the Food and Drug Administration’s webpage, "Research has shown that 50 percent or more of American adults use dietary supplements on a regular basis… The law defines dietary supplements in part as products taken by mouth that contain a "dietary ingredient" such as vitamins, minerals, amino acids, and herbs or botanicals, as well as other substances used to supplement the diet."
Recent research has shown that some foods, beverages and dietary supplements don’t mix well with prescription drugs. Some food and beverages or dietary supplements may interact with prescription drugs affecting the ability of the drug to work as it should or cause unwanted side effects. People who take cholesterol-lowering medications have been cautioned about drinking grapefruit juice while taking the medication. The FDA says: "Grapefruit juice shouldn't be taken with certain blood pressure-lowering drugs because grapefruit juice can cause higher levels of those medicines in your body and side effects from the medicine could occur." Grapefruit juice can cause side-effects when used with other medications as well. Extreme cautions exist about drinking alcohol while taking prescription drugs—as it may magnify or decrease the effect of the medication causing unwanted serious side-effects.
A number of cautions exist about consuming foods, such as dairy products, chocolate or coffee (caffeine) when taking certain medications, but less is known about which dietary supplements interact with drugs. According to an article by Judy Hevrdejs in The Chicago Tribune, March 14, "People who take digoxin for their heart may need to steer clear of St. John's Wort and large amounts of black licorice (that contains glycyrrhizin)." People who take ACE-inhibitors for blood pressure have been warned to go easy on high-potassium containing foods, such as bananas.
"Food and supplement interactions become especially important as the number of drugs taken increases," Shiew Mei Huang, acting director of FDA’s Center for Drug Evaluation and Research Office of Clinical Pharmacology, notes. Many elderly people take more than one medication. A survey she cites published in the Journal of the American Medical Association found in the population surveyed aged 57 and older in the U.S., "at least 80 percent use at least one prescription drug. Half use OTC drugs, and some use dietary supplements."
Frequently contraindications and cautions are listed on instructions accompanying prescription medications, and they use medical jargon which is often difficult to understand. With dietary supplements, there are fewer cautions or warnings, other than a disclaimer on the label, and they have not been evaluated by the FDA. In addition dietary supplements have not been tested with the same rigor as medicines in the marketplace, according to Professor Hartmut Derendorf, head of the University of Florida, Gainesville’s College of Pharmacy, Pharmaceutics Department. Derendorf encourages people to work with their doctor and pharmacist. Especially when a person begins taking a new medicine while they are taking dietary supplements, it’s always wise to ask their pharmacist and physician if they know of any reason why you should not mix the supplement and the medicine. Derendorf recommends telling them about the use of dietary supplements and looking for specific food interactions that are known for the medication prescribed, as well as keeping a record of all prescription and over-the-counter medications a person takes.
The bottom line is that dietary supplements are largely unregulated and unchecked, so buyers should beware, regardless of potential interactions with food, drink, and/or prescription drugs. And, when adding into the equation food,drink and prescriptions, the resulting cocktail could be hazardous. Do as much research as possible, but always talk to your physician about the supplements you are taking.