CANCER
August 24, 2012

Grapefruit Boosts Cancer Drugs' Effects

A glass of grapefruit juice enhanced the effect of an anti-cancer drug. And with no added side effects.

Grapefruit has long been hailed as a wonder food, helping people with weight loss and reducing the risk of diabetes, among other health benefits. Now, a study finds that adding eight ounces of grapefruit juice to one’s diet when taking a cancer drug may reduce the amount of the drug needed to be effective.

Foods like grapefruit can affect how the body metabolizes certain compounds. Sirolimus is an anti-cancer drug, and one whose metabolism is slowed by grapefruit. In the current study, a research team had cancer patients take sirolimus by itself, sirolimus plus eight ounces of grapefruit juice, or sirolimus plus another drug, ketoconazole, which is also known to slow sirolimus’ metabolism.

Another benefit, write the authors, is the cost savings that could be realized by “prescribing” grapefruit juice along with certain drug treatments, since less of the drug would be needed to be effective.

They found that for people who took grapefruit juice, sirolimus metabolism was slowed so that its levels in their bodies increased by 350%. For those who took ketoconazole, the levels were even higher, at 500%.

The team also found that the optimal dose of sirolimus alone was 90 mg per week, but because of the significant gastrointestinal side effects they experienced, patients were switched to 45 mg twice a week. People who took ketoconazole alongside the sirolimus only needed about 16 mg of sirolimus per week to keep the same levels in their blood. People who drank grapefruit juice only needed between 25 and 35 mg of sirolimus per week, instead of 90 mg, to maintain the same levels of the drug.

The greater benefit of grapefruit juice is that it does not pose any risk of overdose, and is totally non-toxic.

"This is the first cancer study to harness this drug-food interaction," the authors wrote.

One possible drawback is that the potent ingredients in grapefruit juice can vary depending on the type of juice. The authors point out that an earlier version of the study used canned juice, which was found to contain none of the active ingredients, so they switched to a frozen concentrated version.

Another benefit, write the authors, is the cost savings that could be realized by “prescribing” grapefruit juice along with certain drug treatments, since less of the drug would be needed to be effective. And, of course, using less of a drug that poses the risk of side effects is always a benefit to the patient.

More studies will need to be done to figure out exactly what amount of grapefruit juice, or its extract, will be most effective in cancer treatment. Additionally, a method for standardizing the dose will also be critical, so that patients are actually getting a known quantity. That said, the research is certainly an exciting step in designing effective cancer treatments – ones that use the least amount of a given drug but have the greatest potency.

The study was carried out by a team at the University of Chicago Medical Center, and is published in the journal, Clinical Cancer Research.

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