OnHealth What Could Possibly Be Bad About Grapefruit

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Monday, January 08, 2001

What Could Possibly Be Bad About Grapefruit?

They -- and Other Citrus Fruits -- Could Interact With Many Medications

By Elaine Zablocki

WebMD Medical News

Reviewed by Dr. Tonja Wynn Hampton

Jan. 5, 2001 -- Grapefruit juice is supposed to be good for you, but that might

not always be the case. Drinking grapefruit juice together with certain

medicines can increase blood levels of the drug to harmful levels, according to

an editorial in the January issue of the journal Nature Medicine.

" [C]itrus fruits contain many substances other than vitamin C and some of them,

such as grapefruit and Seville oranges, can be dangerous if you're taking

certain medications, " writes J.K. Aronson, of the university department of

clinical pharmacology at Radcliffe Infirmary in Oxford, England.

So why is grapefruit getting a bad rap? Grapefruit juice inhibits a chemical in

the intestine needed to break down many drugs in the body. The absence of this

chemical can lead to higher blood levels. In effect, the drug becomes more

potent.

This effect has been observed in nearly all calcium channel blockers, a group of

drugs used to control blood pressure. Some of them include Plendil, Procardia,

and Nisocor. The effect has also been seen in Sandimmune, a drug that suppresses

the immune system and sedatives, such as Xanax and Valium. The editorial also

warns about the AIDS drug Invirase.

Other classes of drugs which may potentially interact with grapefruit juice

include painkillers, antihistamines, steroids, and drugs for asthma. However,

this doesn't mean there's a problem with every drug in these categories -- some

interact with grapefruit juice, while others do not.

This means, if you like to eat grapefruit or drink grapefruit juice, talk with

your doctor when starting a new medication. And ask your pharmacist about the

latest information on food-drug interactions for all the medicines you take.

" Grapefruit does interact with some medications, and anyone who's taking calcium

channel blockers or statins [for high cholesterol] needs to talk with their

physician or pharmacist about this issue, " Bill Stinson, PhD, tells WebMD.

" However, there are so many positive constituents in grapefruit ... that

consumers shouldn't cut it out of their diets completely. " Stinson is scientific

research director for the Florida State Department of Citrus.

Burstein, PharmD, agrees. " This is not a cut-and-dry issue, " he says.

" It's similar to drug-drug interactions. We often prescribe two medications

together even though they interact, because we know we can manage the

interaction. " Burstein is a pharmacokineticist at the National Institutes of

Health Clinical Center's Pharmacy Department, in Bethesda, Md.

Now, he says, doctors and patients need to take possible interactions with

grapefruit juice into account, too. " Recently, I spoke to a woman who loves

grapefruit juice, and takes Tegretol for a seizure disorder. I didn't tell her

to avoid all grapefruit juice. I did say it may be necessary to monitor and

adjust her dosage appropriately. "

Aronson also warns against megadoses of vitamin C supplements. " [N]o matter how

much [vitamin C] you take, all you do is increase the concentrations in your

urine and gut, and that can cause adverse effects ... [such as] nausea,

abdominal cramps, and diarrhea, " he writes.

But Edman, DSc, makes another point. " The studies on vitamin C excretion

were done on healthy people, so they may not tell us about the possible benefits

of higher doses when someone's ill. " Edman is a clinical nutritionist at the

Center for Integrative Medicine at Jefferson University Hospital in

Philadelphia.

" In my opinion, an optimal amount [of vitamin C] is between 300 and 1,500 mg per

day, " he says. " For many people, the lower amount is probably enough, but I want

to leave the door open so people who need higher levels due to a current

illness, or a family history of illness, will not feel hesitant about taking

it. "

Everyone should try to follow an optimal diet plus supplements to fit their

particular circumstances, Edman says. " Too many people are taking supplements

without even knowing why they're taking them. " He adds that a diet rich in

natural sources of vitamins C and E is an essential foundation for health.

The bottom line? " You can't compensate for a poor diet by taking supplements. "

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