No doubt about it — grapefruit is good for you!  It’s a vitamin C-rich citrus fruit that’s low in sugar and contains vitamin A, potassium and fiber.  It has a low glycemic index and does not spike your blood sugar when you eat it.  The pink and red varieties also contain lycopene.

It’s definitely a nutritious health-promoting food.

It even had a whole weight-loss diet created around it called the “grapefruit diet!”  However, research has proven that grapefruit doesn’t have any magical weight loss properties, so don’t eat it just to lose weight.

But … There is a grapefruit-medication interaction.

Grapefruit enhances the effects of many medications, over 85 at last count; this is sometimes called the “grapefruit effect.”  Taking grapefruit (or its juice) along with certain medications, even a day apart, can increase the risk of side effects.

For example, when taken with certain medications to lower blood pressure, it lowers blood pressure too much.  This causes lightheadedness and other symptoms.

Another example is when taken with certain birth control pills, women have a higher risk of blood clots.

Grapefruit affects the metabolism of some of the following categories of medications:

• Blood pressure
• Birth control
• Chemotherapy
• Anti-infection
• Cholesterol-lowering
• Immunosuppressive and anti-rejection
• Urinary tract agents
• Some over-the-counter cough medication

When the medication is taken within 24-72 hours of consuming grapefruit or its juice (yes, up to three days later!), there can be an interaction and potential side effect.  In fact, for half of the medications affected, the grapefruit effect can be serious.  Serious effects include heart and muscle issues and kidney toxicity, to name a few.

How does grapefruit interact with medications?

Grapefruit (as well as Seville oranges, limes, and pomelos) contain a compound called “furanocoumarin.”  It’s this compound that inhibits (stops) an enzyme in our gut (enzyme CYP 3A4) from working properly.

When working properly, this enzyme breaks down and metabolizes many compounds we ingest, including dozens of medications.

When the enzyme is inhibited, such as when we’ve consumed grapefruit, this slows down the enzyme.  This leads to slowing down the rate these medications are metabolized and eliminated from the body.

If you slow down metabolism and elimination, this leads to higher than normal levels of medications in the blood (up to 137% higher!).  This “enhances” their effect and can cause those side effects.

When medications are prescribed at certain doses to be taken within certain time frames, this is based on the medication being metabolized normally — not way-too-slowly.

If you need to replace grapefruit or its juice in your diet, try another fruit or vegetable.  Or, talk with your doctor about swapping your current medication for another medication that’s not affected by grapefruit.

Since one glass of grapefruit juice can affect the enzyme’s function for over 24-hours, it’s advisable to stop eating the grapefruit or drinking its juice altogether while you’re taking certain medications.

If you love eating grapefruit or drinking its juice and are taking medications, definitely speak with your doctor or pharmacist to see if this affects you.  Many medications are not metabolized by the CYP 3A4 enzyme, and even if they are, this grapefruit effect may not pose a serious risk for all of those medications.

Do you know someone who loves grapefruit or its juice, and is taking medications that have the grapefruit effect?  Please share this post to let them know that they should double-check with their doctor or pharmacist before enjoying this awesome fruit.  And please share any personal experience you’ve had with the grapefruit effect below.  We always love to hear from you.