Kale is great for you—usually. If you’re taking some drugs, it might cause some bad side effects. Same with grapefruit juice and other healthy foods and drinks, and some other common treats.
Turns out, what you take with your medications can be just as important as taking them in the first place. Here’s why: Research shows that some foods and drinks can rob your medications of some of their powers. Or they can cause serious, even life-threatening, reactions.
Here’s a list of seven foods that don’t mix well with common drugs. Don’t worry if you see a favorite food or drink here. You probably won’t have to give it up; you might just need to cut back or wait a few hours to indulge. This is a partial list; to be safe, ask your doctor and pharmacist about possible food interactions with any drugs you take. Also read the warnings in inserts that come with your prescription meds, and in the fine print on over-the-counter drugs.
Don’t mix with:
What can happen:
ACE inhibitors and so-called “potassium sparing” diuretics can increase the amount of potassium in your body. But too much potassium can cause an irregular heartbeat and heart palpitations. So people who take those drugs should avoid large amounts of food high in potassium, including bananas, oranges, green leafy vegetables, and salt substitutes such as Morton Lite Salt.
Don’t mix with:
Blood thinners such as warfarin (Coumadin).
What can happen:
Kale and other greens, including broccoli, cabbage, spinach, and brussels sprouts, are rich in vitamin K, which can reduce the drug’s anti-clotting effects. It’s good to eat a balanced diet with lots of greens, but don’t suddenly start drinking a daily kale smoothie without telling your doctor.
Don’t mix with:
Digoxin (Lanoxin), used to treat heart failure and abnormal heart rhythms.
What can happen:
Glycyrrhizin, a component of black licorice, can cause irregular heartbeat or even death when combined with digoxin. Licorice also appears to make certain drugs less effective. The list includes blood-pressure medications, blood thinners, pain relievers, and birth-control pills. Be careful if you eat a lot of it (only the real stuff counts; some candy is just licorice-flavored, so look for “licorice extract” on labels) or if you take licorice-root supplements for heartburn.
Don’t mix with:
Tetracycline antibiotics (Sumycin).
What can happen:
Calcium—from dairy foods such as milk, yogurt, and cheese, and calcium supplements and fortified foods—can prevent the body from absorbing the drug. In general, tetracycline works better if taken one hour before or two hours after eating.
Don’t mix with
Cholesterol drugs such as atorvastatin (Lipitor) and lovastatin (Mevacor).
What can happen
Drinking grapefruit juice can raise the level of the drug in your bloodstream and increase the risk of side effects, especially leg pain. Grapefruit and grapefruit juice can interfere with other drugs, too.
Don’t mix with:
Drugs such as metronidazole (Flagyl) and linezolid (Zyvox), used to treat bacterial infections.
What can happen:
If you eat or drink too much of anything that contains the amino acid tyramine, your blood pressure could spike. Tyramine is found in foods that are aged, pickled, fermented, or smoked, such as processed cheeses, anchovies, and dry sausage. It’s also in avocados, bananas, chocolate, and alcoholic drinks.
Don’t mix with:
Thyroid drugs such as levothyroxine (Levothroid, Levoxyl, Synthroid).
What can happen:
Walnuts, soybean flour, cottonseed meal, and high-fiber foods can prevent your body from absorbing those medications. So if you eat a high-fiber diet, you might need a higher dosage. One study found that the drugs were better absorbed when taken at bedtime rather than a half-hour before breakfast, which is what is usually recommended in the instructions.
Pay attention to those alcohol warnings!
Many medications come with instructions not to drink alcohol while you’re taking them. It’s an important warning—even one little glass of wine could be too much. Here’s why: Alcohol alone can make you drowsy, light-headed, and less coordinated; mixing it with certain drugs can magnify those effects. Even worse, it can cause serious problems, including internal bleeding and breathing and heart problems. And alcohol can make a drug less effective, even useless, or it can make a drug toxic. For example, just a few drinks mixed with acetaminophen (Tylenol) can damage your liver.
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Like the foods and drinks above, some dietary supplements, including vitamins, minerals, and herbals, can cause problems if you take them with some drugs. Even a multivitamin with iron can negate the effects of many drugs. But herbs are the worst offenders, and St. John’s wort might be the worst of all. For example, combining St. John’s wort with over-the-counter cough medicines or prescription antidepressants or migraine drugs can cause serotonin syndrome, a dangerous condition that can cause rapid blood-pressure changes, confusion, muscle spasms, and even death.
A 2012 review of 10 years of published data about interactions between drugs and supplements revealed just how big the problem really is. Researchers found almost 1,500 documented interactions involving a total of 509 drugs and 213 supplements.
The most common drugs involved in the interactions were, in order, warfarin (Coumadin), insulin, aspirin, digoxin (a heart drug), and ticlopidine. The supplements that turned up most often were St. John’s wort, magnesium, calcium, iron, and ginkgo biloba.
Bottom line: When you tell your doctor and pharmacist what drugs you take, don’t forget to also mention supplements. They might not be harmless!
This article and related materials are made possible by a grant from the state Attorney General Consumer and Prescriber Education Grant Program, which is funded by the multi-state settlement of consumer-fraud claims regarding the marketing of the prescription drug Neurontin (gabapentin). The aricle was adapted from ShopSmart magazine.
Consumer Reports has no relationship with any advertisers or sponsors on this website. Copyright © 2007-2013 Consumers Union of U.S.
