Health Professionals Say Grapefruit Juice-Drug Interaction Overstated

Paul Kimpel

Christine Waddill, (352) 392-1761 x-227
Elaine Turner (352) 392-1991 x-224 (352) 392-1991 x-224
Paul Doering, (352) 265-0408
Eric Boomhower mailto:eboomhow@citrus.state.fl, (863) 499-2452

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GAINESVILLE, Fla. — It wasn’t long ago that the media was touting the benefits of grapefruit juice as part of a heart- healthy diet. Now, the beverage is again in the news, but this time the focus is on a negative aspect: its unique ability to interfere with the action of certain prescription drugs.

Many healthcare providers acknowledge that the ‘grapefruit- juice effect’ is real, but say the subject has been blown out of proportion.

Elaine Turner, a University of Florida assistant professor of human nutrition, said food- drug interactions must be applied on an individual basis.

“Certain food-drug interactions — such as green vegetables combined with blood- thinning drugs, or grapefruit juice and blood-pressure drugs — affect everyone differently,” Turner said. “It depends on a person’s dietary habits and other factors.”

In an effort to present consumers and health professionals with an unbiased assessment of the situation, UF has formed a committee to create educational materials that address food-drug interactions.

Christine Waddill, dean for extension, said that UF’s Institute of Food and Agricultural Sciences, together with UF’s College of Pharmacy, expects to publish the materials by January 2002. She said the committee will put extra emphasis on clarifying the grapefruit juice issue.

Turner, who is a committee member, said consumers may get confused when they hear conflicting or overstated health messages.

“It is a bad idea for health professionals or the media to make sweeping statements about food-drug interactions or any other health topics,” Turner said. “News reports should only be a starting point for consumers, not an end-all.”

She said most doctors and pharmacists are aware of these interactions and take appropriate precautions.

“When doctors prescribe or adjust medications, they monitor blood pressure, blood-clotting times and similar issues,” Turner said. “If a person has been drinking grapefruit juice all their life, and begins taking a drug that is affected by the juice, then a doctor will adjust medications based on that information. Simply because there is a food-drug interaction does not mean a person has to deny themselves foods they enjoy.”

Paul Doering, a UF professor of pharmacy, amplified Turner’s comments, saying it could be dangerous for people to make significant changes in their diet based on a media report.

“If a person has been taking a particular blood- pressure drug while drinking grapefruit juice daily, and then suddenly stops drinking the juice, absorption of the drug may drop dramatically,” Doering said. “This can cause a rise in blood pressure. Likewise, if a person who rarely drinks grapefruit juice suddenly consumes several glasses, that could spike drug levels upward, which can cause a sudden drop in blood pressure.”

Doering said the key to food-drug interactions is consistency.

“If you have been taking a medication and drinking grapefruit juice, it is likely that your system has adjusted to that interaction,” Doering said. “Making significant changes to that routine without consulting a doctor or pharmacist would not be advisable.”

Doering said some doctors and pharmacists recommend separating certain drugs from grapefruit juice by two hours, but added that some studies have shown that grapefruit juice is active as long as 12 hours after consumption. Critics of those studies said that participants drank a quart of juice a day to cause the effect, but Doering said other studies showed that one 8-ounce glass was enough.

With certain drugs, such as some calcium-channel blockers and HIV-1 protease inhibitors, Doering said grapefruit juice improves absorption, which can be helpful to the patient if monitored correctly.

However, he stressed that the subject of grapefruit juice needs further studies before general recommendations can be made.

“It is more difficult to generalize about this interaction versus one such as antibiotics and milk,” Doering said. “With milk, we have enough evidence to say don’t drink it at the same time you take certain antibiotics. With grapefruit juice, which affects some drugs that are taken for a lifetime, we don’t have the conclusive studies to make that type of recommendation.”

The grapefruit juice phenomenon was discovered in 1989, and since that time scientists have tried to isolate the active compounds in the juice but haven’t identified them all. The grapefruit-juice effect occurs because of components in the juice that inhibit the breakdown in the intestines of certain drugs, thereby increasing drug absorption. Most studies have been done with concentrated grapefruit juice, and it is thought that the active components are intensified during the concentration process. Studies on eating grapefruits have shown mixed results: some showed an effect and some did not.

In a positive spin on the phenomenon, some researchers said that if the active component of grapefruit juice could be extracted and standardized, it could be used to save consumers money on drug costs because it would cause some drugs to be more readily absorbed, allowing people to take a lower dosage.

For now though, the beleaguered juice has seen a 16 percent decline in retail sales during the past year and is having an acute image crisis.

According to Eric Boomhower, marketing director for the Florida Department of Citrus, part of the problem is that some so-called ‘medical experts’ have advised consumers to avoid grapefruit juice altogether if they take any drugs.

“That’s simply ridiculous,” Boomhower said. “It is a small group of drugs that is affected by this interaction, and people need to know that.”

Regarding the weaker sales figures, he acknowledged it could not be entirely blamed on news about the drug interactions.

“Retail prices rose by 7 percent last year, so a decline in sales was expected,” Boomhower said. ” However, when you combine that with the overstated media reports, it is obvious we must take action to accurately inform people about this subject.”

Boomhower said the Florida Department of Citrus has set aside $500,000 to sponsor research and run a public relations campaign on the subject.



Posted: July 3, 2001

Category: UF/IFAS

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