Grapefruit and medications

A note on grapefruit: Handle with care.

In the e-Alert “Pass the Pamplemousse” (3/9/04), I told you how eating grapefruit or drinking grapefruit juice before each meal may help manage insulin levels, which makes it easier to lose weight.

In response, a number of HSI members sent e-mails to remind me of one important detail about grapefruit consumption.

A member named Cheryl wrote, “Aren’t there interactions with grapefruit juice that impede absorption or alter the benefits of certain supplements & substances ingested at the same time? I would like to hear from you on these issues so I’m not adding benefit in one area & taking from another.”

And a member named Kathryn voices the same concern, along with some useful information: “Depending on the medication, including antibiotics and hormones, grapefruit may either increase the activity of the drug OR decrease the effectiveness. A simple way to get around this is to wait 30 minutes to an hour after eating grapefruit or drinking grapefruit juice before you take your medications.”

Cheryl and Kathryn are both on the right track. Grapefruit contains phytochemicals that may impede an enzyme system in the small intestine. The result: When grapefruit or grapefruit juice is consumed at the same time that certain drugs are taken, the absorption of the drugs is increased dramatically, and sometimes dangerously. This is especially true of calcium channel blockers (taken for high blood pressure), immunosuppressant drugs, statin drugs for high cholesterol, and various medications for anxiety, insomnia and depression. Curiously, some antihistamine drugs are increased, while others are decreased.

Vitamins and other dietary supplements are a different story. When I asked HSI Panelist Allan Spreen, M.D., if grapefruit consumption might alter the absorption of nutrients in supplements, he said he didn’t think it would be a factor, and added, “Since the problem is the tendency to increase the action of the drugs it would be nice to have that effect with supplements. Alas, I fear it’s not to be.”

From what I’ve read, Kathryn’s suggestion is good advice: Try to put an hour or so between grapefruit consumption and drug intake. And to be on the safe side, if you’re taking any prescription drugs, check with your doctor before increasing your daily intake of grapefruit.

A member named Pam has one more question about the grapefruit e-Alert: “What does pamplemousse mean? I have checked every dictionary I have and it’s nowhere to be found. It’s driving me crazy!”

“Pamplemousse” is French for “grapefruit.” So now you know how to order grapefruit on your next trip to Paris or Provence.

To Your Good Health,

Jenny Thompson
Health Sciences Institute