It was a common sight in our house when I was growing up to see half a grapefruit waiting for me on the breakfast table each morning. Although I never liked orange juice, I adored the sweet-tart flavor of a pink grapefruit with a bit of sugar sprinkled on top. However, according to a study published in the Canadian Medical Association Journal, scientists have recently found that certain organic compounds present in grapefruit may cause serious life-threatening interactions with a number of prescription drugs.
For a number of years, experts have understood that grapefruit can react with certain drugs, however, a new study performed by researchers at the Lawson Health Research Institute in Ontario, Canada, have found that the number of drugs grapefruit interacts with has been rising steadily. According to the study’s lead author, David Bailey, "The number of drugs on the market with the potential to produce serious adverse and in many cases life-threatening effects when combined with grapefruit has markedly increased over the past few years from 17 to 43 in four years." Grapefruit may have an interaction with upwards of 85 drugs, 43 of which can cause serious side effects, according to Bailey.
The chemicals in grapefruit that scientists have pinpointed as being the cause of the problem are called furanocoumarins. These act in the gut to neutralize an enzyme that breaks down some drugs that act to reduce the amount of drugs’ absorption. In effect, it causes an overdose of what would normally be considered a safe amount of a drug. In addition to grapefruit and grapefruit juice, furanocoumarins can also be found in limes, lemons, celery and Seville oranges.
About 10 years ago researchers had been investigating whether alcohol could interact with the hypertension drug felodipine and had used grapefruit juice to mask the taste of the alcohol. They noticed that the felodipine levels in the blood were significantly higher than in previous studies using the same amount of the drug, which is when they discovered the grapefruit interaction issue.
Even a single serving of grapefruit can have a significant effect. One glass of grapefruit juice can block the action of drug-neutralizing enzymes for as much as 24 hours. So if you take a medication every day, there is no safe time when you could consume grapefruit. For example, if for three consecutive days someone takes a cholesterol-reducing statin drug on the same day as drinking one 200 ml glass of grapefruit juice, the amount of the drug in their bloodstream increases by over 300 percent. Bailey said, "Taking one tablet with a glass of grapefruit juice is like taking 20 tablets with a glass of water. This is unintentional overdosing. So it's not surprising that these levels go from what we call therapeutic to toxic."
There are not many doctors who will ask if their patient eats grapefruit before they prescribe a medication. The study’s researchers note, "Unless healthcare professionals are aware of the possibility that the adverse event they are seeing might have an origin in the recent addition of grapefruit to the patient's diet, it is very unlikely that they will investigate it. In addition, the patient may not volunteer this information. Thus, we contend that there remains a lack of knowledge about this interaction in the general healthcare community."
CBC News reports that the researchers said, "Many of the drugs are common, such as some cholesterol-lowering statins, antibiotics and calcium channel blockers used to treat high blood pressure. Others include agents used to fight cancer or suppress the immune system in people who have received an organ transplant. People older than 45 buy the most grapefruit and take the most prescription drugs, making this group the most likely to face interactions."
Efforts are currently underway to develop grapefruit and grapefruit juice that is free of furanocoumarins, however, would it not make more sense for doctors to just reduce the amount of the drug they prescribe for their patients who eat grapefruit?
Grapefruit is a healthy addition to almost any diet. They are rich in phytonutrients and antioxidants such as vitamin C and lycopene (in pink and red grapefruit). These compounds boost the immune system and have been shown to reduce the risk of cancer. Eating grapefruit regularly can also keep you from getting kidney stones and can lower cholesterol.
There are many benefits to eating grapefruit, so if you are taking prescription drugs speak with your doctor about any possible interaction, and if there is one, ask if your dose can be reduced so you can continue to enjoy the health benefits that grapefruit provides.