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Food for Naught

Why grapefruit isn’t a great fruit when you’re taking some medications

By Scott LaFee   |   March 05, 2014

If you take a statin – a hugely popular class of drugs taken by more than 35 million Americans – you should take note of some tiny script printed on the container label: “Do not take with grapefruit or grapefruit juice.”

It seems an odd warning. Grapefruit seems so, well, good for you. The citrus is vitamin-rich, particularly in A and C, and in nutrients like lycopene (a powerful antioxidant) and salicylic acid, which helps break down inorganic calcium in the body and reduce symptoms of arthritis. Grapefruit is commonly touted as helpful for treating colds, gallstones and infections and its dietary fiber, called pectin, promotes better digestion. Grapefruit is also supposed to rev up your metabolism, boosting the calorie-burning benefits of some diets.


According to a study in the Journal of Agricultural and Food Chemistry, a daily serving of grapefruit lowers levels of “bad” LDL cholesterol by 15.5 percent and triglycerides by 27 percent.


Of course, lowering cholesterol is what statins are famously supposed to do, but consuming statins and grapefruit or grapefruit juice is not wise. In fact, it may be downright dangerous.

Grapefruit and grapefruit juice interact with dozens of drugs, 85 at last count and rising. Many of these interactions produce adverse effects; some potentially fatal. A Canadian study in 2012 reported that the number of known drug-grapefruit interactions with possibly fatal side effects grew from 17 to 43 in just four years.

The problem is that grapefruits are rich in furanocoumarins, organic compounds that block an enzyme produced by the liver and intestines to break down certain medications in the body. Without this enzymatic activity, levels of these medications can grow to harmful, even toxic, levels.

The list of interacting medications is diverse. It includes drugs used to treat cancer, diabetes, infections, inflammation, cardiovascular problems, pain, immune response problems, AIDS, even birth control and hormonal imbalances.

All drugs that interact with grapefruit are taken orally, but their effect varies. With some medications, a single serving of grapefruit can exponentially multiply the amount of drug in the body. For example, taking simvastatin, a popular statin drug used to lower cholesterol, with a seven ounce glass of grapefruit juice once a day for three days results in a 330 percent increase in the concentration of the drug in the body compared to taking the statin with water. The high amount of simvastatin in the body may result in rhabomyolysis, a breakdown of muscle tissue that lead to the release of muscle fiber into the bloodstream, ultimately causing kidney damage or failure. 

Other drug-grapefruit interactions are linked to an increase in heart rhythm called torsade de pointes, which can be fatal.

Grapefruit isn’t the only troublemaker here. Pomelos (a hybrid between an orange and an Asian fruit called Citrus maxima) also contain furanocoumarins, as do Seville oranges (used in marmalades) and limes. These fruits have not been studied as much as grapefruit so it’s not known if they pose the same degree of risk.

It should be noted that not all medications in a drug class necessarily interact with grapefruit. Sometimes it’s possible to find a grapefruit-friendly drug that achieves the same health benefit. Here are some rules of thumb to remember:

  • If you take oral medications of any kind, check with your doctor or pharmacist to see if they interact with grapefruit. Assess the potential side effects. Some drugs are less effective if mixed with grapefruit.
  • Remember grapefruit isn’t the only food that may cause unwanted interactions. Pomelos, limes and Seville oranges may be problematic as well.
  • It’s not sufficient to simply avoid taking your medication with grapefruit and/or grapefruit juice. You must avoid consuming the fruit in any form for the duration that you are taking your medication.
  • If grapefruit is an absolutely essential part of your life, ask your doctor or pharmacist about alternative medications that do not interact with the fruit.



Grapefruit is singled out here, but the risk of adverse drug interactions is broad. There are many combinations of foods, drinks and other drugs that can cause problems.


Alcohol is an obvious example.

Eating chocolate and taking a monoamine oxidase (MAO) inhibitor drug like Nardil or Parnate (to treat depression) can result in a sharp rise in blood pressure. Likewise, MAO inhibitors don’t mix well with consumption of processed meats and aged cheeses.

According to researchers at the National Institutes of Health, roughly half of American adults take some form of dietary supplement (vitamins, minerals, amino acids, herbs, botanicals) on a regular basis. Some of these supplements have been shown to interfere with certain medications. Among them: St. John’s wort, vitamin E, ginseng and ginkgo biloba.

Not surprisingly, drugs can interact with other drugs and many Americans are on multiple medications. According to the Institute for Safe Medication Practices, almost 40 percent of the United States adult population  take four or more medications.

  1. The list of known drug-drug interactions is too long and complex to cite here, but there are, again, a handful of simple rules that will help minimize the risk of a drug-drug interaction.
  2. Always read drug labels carefully. Look for warnings.
  3. Keep medications in their original containers so you can easily identify them.
  4. Ask your doctor about any special issues or considerations when you receive a new prescription. Ask about potential risks with interactive foods, drinks, supplements or other drugs.
  5. If you’re purchasing a new or unfamiliar over-the-counter drugs (example: an antihistamine), check with a pharmacist to see if there are interaction concerns.
  6. Use one pharmacy for all of your needs.
  7. Make sure your doctor and pharmacist are up-to-date on everything you take. Bring a complete list of your prescriptions and any regularly consumed OTC drugs or supplements when you visit your doctor.