AJN grapefruit reminder criticized as unscientific

In the December 2004 issue of the journal clinical associate professor of nursing Amy Karch of the University of Rochester Medical Center's School of Nursing claimed that the consumption of grapefruit juice in conjunction with certain medications could cause serious illness.

She also asserted that, in women taking the contraceptive pill, reduced efficacy brought about by the fruit may result in pregnancy.

"The potential of drug interactions with grapefruit juice has been out there a long time, but most people just aren't aware of it,"​ said Karch.

Karch's paper cites the example of a man who began consuming grapefruit juice when wintering in Florida and subsequently became ill with kidney failure due to the interaction with cholesterol-lowering drug Lipitor.

However the FDOC has responded by saying that the allegations are made without appropriate scientific support.

"Many scientific studies showed grapefruit interactions with some specific drugs, but I cannot find any evidence that death or pregnancy resulted from grapefruit juice,"​ said Dr Hartmut Derendorf, distinguished professor of the University of Florida's College of Pharmacy.

While grapefruit may increase the levels of some components of birth control pills, the effectiveness is not decreased so as to result in pregnancy, he added.

Grapefruit juice is metabolized in the liver by the cytochrome P-450 3A4 enzyme - the same enzyme that breaks down some medications. Taking these medications together with grapefruit juice can cause the liver to be 'overloaded', preventing it from breaking down the drugs.

With some medications, such as Lipidor, this could have fatal consequences, leading to a breakdown of the body's muscles and possibly even kidney failure, says Karch.

With others she claims it may reduce the effectiveness of the drugs - a consequence that could also have life-threatening implications, for example in heart patients taking blood-pressure lowering medication.

Derendorf, on the other hand, points to three conclusions of research carried out by Dr David Greenblatt of Tufts University School of Medicine:

While some prescription medications may interact with grapefruit, most do not; within each drug class there are generally non-interacting alternative medications; and it is safe to consume grapefruit juice while taking any over-the-counter medication.

Very little research has been carried out into the interaction between grapefruit-based supplements, such as grapefruit seed oil and grapefruit pectin fiber.

Grapefruit juice is drunk by many people for its high vitamin C content, as well as potassium and beta-carotene. The fruit also forms the bases of several weight loss programs.

In January 2004 researchers from Scripps Clinic reported on the results of a 12-week pilot study​ of the fruit, which indicated that it may aide weight loss by impact the body's insulin levels and speeding up metabolism.