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Benefits of Grapefruit Diet Turn Lethal for Some

Effects of grapefruit on certain medications can cancel out benefits of grapefruit and drug


The only time I ever had fresh squeezed orange juice as a child was when our relatives in Florida sent my family a case of assorted citrus fruit at Christmas. My sisters and I loved the intoxicatingly sweet orange juice, but our father loved the slightly bitter grapefruit juice.

Flash forward 50 years and I now must tell my dad he cannot enjoy the benefits of grapefruit in his diet. When combined with several of the medications he takes, the effects of grapefruit could make the drugs toxic to him.

Whether you have the occasional sectioned grapefruit half with a maraschino cherry on top or are eating it three times a day trying to lose weight on the grapefruit diet, new research shows it can be harmful to your health if you are taking certain medications

The study was published in the Canadian Medical Association Journal and found the number of drugs that react with grapefruit is much greater than what was previously recognized. David Bailey, PhD, a clinical pharmacologist at the Lawson Health Research Institute in Ontario, and his colleagues analyzed 161 research studies showing changes in drug effects after ingesting grapefruit.  They also evaluated 29 drug monographs and prescription information sheets for warnings about interactions between grapefruit and medication.

In their review they identified 85 drugs currently on the market that may interact in some way with grapefruit, with half of them having the potential to cause sudden death. Only 17 drugs were believed to have life-threatening effects four years ago.

Here's a Quick Question & Answer Guide to how medications can interfere the the benefits of grapefruit.

What Can Happen When You Mix Certain Mediations With Grapefruit?

Unintentional over dosing. Taking one pill with a glass of grapefruit juice can increase the potency of some drugs to the equivalent of five or 10 pills  

Loss of drug efficacy. Some drugs don't work at all if they interact with grapefruit.

Are There Any Other Dangers?

Early symptoms of an interaction, such as gastrointestinal bleeding, kidney failure, or respiratory distress, can be misdiagnosed and lead to costly testing if the connection is not made. Those 45 and older are the most vulnerable since they take the most medications and are also the biggest consumers of grapefruit and grapefruit juice.

Which Medications Are of Concern?

Many commonly prescribed medications from a variety of different drug categories interact with grapefruit. Not all of the drugs in a particular class are suspect, but the list includes some anticancer agents, anti-infective agents, cholesterol-lowering drugs, cardiovascular drugs, gastrointestinal, immunosuppressants, drugs affecting the central nervous system, and urinary tract agents.

How Much Grapefruit Does It Take?

As little as 6 - 8 ounces of grapefruit juice can cause a drug reaction. The studies did not distinguish between white and pink grapefruit or the size of the fruit.

How Soon Before or After Taking the Medication Can the Grapefruit Have This Effect?

Effects can be experienced if the drugs and grapefruit are taken at any time in the same day, even if separated by 12 or more hours. If a single serving of grapefruit juice is consumed for three consecutive days with one of the medications it can be fatal.

Can Other Citrus Fruits Have the Same Effect?

Grapefruit was the citrus fruit analyzed in the studies, but the same effects can be caused by any citrus fruit containing furanocoumarins, a compound that interferes with how drugs are absorbed through the intestines.  Other citrus fruits known to contain the compound are limes, Seville oranges (used in marmalade), and pomelos.

What Can You Do?

Read the drug interaction information that comes with all prescription medications. If you don't have it, check with your pharmacist. Report the use of any citrus products to your physician if you are on a listed medication and have any sudden change in your health.