Filling up on grapefruit might help you drop a few pounds, but proceed with caution: It could be hazardous to your health. Turns out, eating grapefruit can cause serious—even life-threatening—side effects if you mix it with any of 43 drugs, according to a new study published in the Canadian Medical Association Journal.
Many of the meds that have been found to be dangerous are completely necessary for treating important and common medical conditions, according to the study. For women, that could include birth control pills, some anti-anxiety drugs, and sleeping pills, according to Joe Graedon, MS, a pharmacologist and co-founder of the website PeoplesPharmacy.com.
The culprit behind all this trouble? Furanocoumarins. This ingredient in grapefruit deactivates an enzyme in the stomach that breaks down drugs, which can cause the amount of the drug in your blood to go up, says Graedon.
“Because the drug isn’t metabolized the way it normally would be, you end up with a greater potential for toxicity,” he says. So, for example, if you’re prescribed a specific dose of a blood pressure pill, that dose alone is meant to keep your blood pressure in check. But if you take it along with grapefruit or grapefruit juice, you might get the equivalent of three, four, or even 10 more pills, he says.
And this isn’t the first time grapefruit has been busted as a health hazard. More than 20 years ago, the same team of researchers that authored this current study discovered the dangerous interaction. But as new meds and new formulations make their way into your medicine cabinet, the number of drugs that you shouldn’t take with grapefruit has grown from 17 to 43—and this is in the past four years alone.
To find out whether you need to keep grapefruit out of your diet, all you have to do is ask your doctor or pharmacist if the drugs you’re taking would react badly with grapefruit, says Graedon. For a complete list of the 43 drugs that have bad side-effects when mixed with grapefruit, check here.