For many people, sipping a glass of grapefruit juice is a refreshing, healthful morning ritual. But it also can be dangerous if you take certain medications along with your breakfast beverage.
Grapefruit juice isn’t the only potential problem. Several foods can interact with prescription and over-the-counter medications.
“Food-drug interactions occur when a drug interacts or interferes with something that you eat or drink, so the medication can’t work the way that it should,” said Julie Berman, a clinical specialist in drug information at Detroit Receiving Hospital in Michigan.
Depending on the drug and food combination, the interaction may make the medication either less effective or more potent. The timing between when you take the medication and when you eat a particular food also can cause an effect. Food can sometimes delay the absorption of certain drugs that should be taken on an empty stomach. But other medications are easier to tolerate when taken with food and can even help them to be absorbed better.
The risk of alcohol
Alcohol interacts with more drugs than most foods do, so it’s important to check with your doctor about whether you can drink while taking your medication. Some interactions may occur even at moderate drinking levels of one to two drinks per day, according to a paper published in the journal Alcohol Research and Health. The greatest risk is over-sedation or drowsiness, but the effects with some medications can be more dangerous.
Caffeine-containing foods and beverages also may interact with drugs by stimulating the central nervous system, resulting in excitability and nervousness.
“Most people are aware that coffee, tea and colas contain caffeine,” says Cynthia Sass, a dietitian at the University of South Florida and a spokesperson for the American Dietetic Association. “But many assume that clear-colored sodas are caffeine free and that’s not necessarily the case. Some brands of orange soda and root beer may also contain caffeine, as well as coffee-flavored ice creams and yogurts.” Unfortunately, caffeine content is not labeled on foods, so if you are concerned about your caffeine intake, contact the manufacturer.
Supplement dangers
Dietary supplements also can interfere with the action of other medications, Sass says. But many people consider dietary supplements risk-free and forget to mention them when doctors ask about which medications and other substances they take. Because more than half of the population takes dietary supplements of some kind, the potential for interaction is widespread.
“Fish-oil supplements, vitamin E supplements and ginko biloba should not be taken by people who are on anticoagulent drugs, for example,” Sass said, “because they have a blood thinning effect and in combination with these drugs may cause excessive bleeding.
“Kava kava has a calming effect so it can enhance that of anti-anxiety drugs. The situation with St. John’s wort is similar because it acts as an antidepressant and the combination can be dangerous for someone already taking an anti-depressant medication.”
So it’s critical that your doctor and pharmacist know about every medication or supplement you are taking.
“Don’t forget to include over-the-counter, non-prescription medications such as aspirin or cold medicine,” Berman said.
Medicine labels and packages also contain interaction precautions, so even though the print is often tiny–OK, unreadable–making the effort to slog through all of it can be a lifesaver.
The accompanying chart describes potential interactions between various medications and foods. It is by no means exhaustive, and the advice contained in it should not override the recommendations from your doctor, pharmacist or dietitian.
Potential food-drug interactions
This chart gives examples of possible interactions but is not exhaustive. It should not replace recommendations from your doctor, pharmacist, dietitian or nurse. If you have questions or concerns about your medication, consult a health-care professional before making any changes.
Medical condition: High blood pressure
Generic medication name: Felodipine, amlodipine, nifedipine, and other calcium channel blockers; diuretics (water pills)
Foods to avoid or limit: Natural licorice; grapefruit juice. Increased potassium excretion, sodium reabsorption and blood pressure.
Possible effects: Can double blood levels of drugs, leading to excessively low blood pressure.
Some diuretics cause a loss of potassium, calcium and magnesium. Other diuretics, such as triamterene, have the opposite effect. If you take triamterene and also eat lots of potassium-rich foods (bananas, oranges, green leafy vegetables, and salt substitutes), it can result in hyperkalemia, which can cause irregular heartbeat.
Medical condition: Allergies, asthma, emphysema, and other chronic pulmonary disorders
Generic medication name: Theophylline, terfenadine
Foods to avoid or limit: Excessive caffeine
Possible effects: Can increase the side effects of theophylline, causing dizziness, nausea, vomiting, convulsions or coma.
Medical condition: Depression
Generic medication name: MAO inhibitors and phenylzine
Foods to avoid or limit: Excessive caffeine and foods rich in tyramine, including aged cheese, avocados, wine, sour cream, chicken livers Combination of caffeine and medication could lead to hypertensive crisis.
Possible effects: Tyramine can cause lethal increases in blood pressure, as well as headache, vomiting.
Medical condition: Infections
Generic medication name: Tetracycline, doxycycline and miocycline; ciprofloxacin and other quinalone antibiotics; penicillin and erythromycin
Foods to avoid or limit: Foods rich in calcium like milk and other dairy products (cheese, yogurt, and ice cream) or calcium-containing antacids; iron supplements; acidic foods like tomatoes and fruit juices; caffeine
Possible effects: Calcium can inhibit absorption of the drug, reducing the antibiotic effect. Calcium will not be absorbed because the compounds bind to each other. Similar binding effect happens with iron supplements, resulting in reduced absorption of iron and antibiotic. Increased stomach acid from acidic foods can destroy the drug in the stomach before it is absorbed.
Medical condition: Osteoporosis
Generic medication name: Alendronate
Foods to avoid or limit: Fruit juice
Possible effects: Prevents absorption of drug in the stomach, rendering it ineffective.
Medical condition: Smoking cessation
Generic medication name: Nicotine gum
Foods to avoid or limit: Fruit juice, caffeine
Possible effects: Interferes with drug’s absorption.
Medical condition: Parkinson’s disease
Generic medication name: Levodopa
Foods to avoid or limit: Foods high in pyridoxine (vitamin B6) should be limited to less than 5 mg per day. Significant food sources of pyridoxine include chicken, fish, pork, liver and kidney.
Possible effects: Can decrease effectiveness of medication.
Medical condition: Pregnancy
Generic medication name: Some iron-containing prenatal vitamins
Foods to avoid or limit: Milk and other dairy foods like cheese and ice cream.
Possible effects: Decreases absorption of iron.
Medical condition: Heart disease
Generic medication name: Blood-thinning agents like warfarin; ACE inhibitors, such as captopril and moexipril; HMG-CoA reductase inhibitors like lovastatin, atorvastatin, cerivastatin, fluvastatin, simvastatin
Foods to avoid or limit: Intake of vitamin K-rich foods, such as broccoli, spinach, kale, turnip greens, Swiss chard, cauliflower, beef and chicken liver must remain consistent. Avoid vitamin E supplements; limit potassium-rich foods and salt substitutes containing potassium; natural licorice; grapefruit juice; foods high in fiber, oat bran and pectin.
Possible effects: Can reduce effectiveness of anticoagulant in preventing blood clots, so maintain a consistent intake of foods that are high in vitamin K, or doctor may need to adjust medication level.
High doses of vitamin E can prolong clotting time and increase the risk of bleeding.
Some ACE inhibitors may increase the amount of potassium in your body.
Can increase levels of drugs in the bloodstream.
You should still include foods containing fiber, oat bran and pectin, but don’t eat them for several hours before or after taking lovastatin.
Sources: American Pharmaceutical Association; Food-Medication Interactions — 11th edition by Z. Pronsky; Food & Drug Interactions brochure by US Food and Drug Administration and National Consumers League
