Grapefruit: The Forbidden Fruit?

Steve Bond 08 Aug

Grapefruit: The Forbidden Fruit?

Grapefruits are an excellent source of Vitamin C, dietary fibre and lycopene.  They are hybrids of two other citrus fruits: The Pomelo and the Sweet Orange and the fruit has become popular since the late 19th century; before that it was only grown as an ornamental plant.  It was first described in 1750 by the Reverend Griffith Hughes and was then and often afterwards called the forbidden fruit, because it was seized upon by those searching for the identity of the original tree of good and evil in the Garden of Eden.  In 1989, a group of researchers at the London Health Sciences Centre was studying the effects of ethanol (alcohol) on a certain blood pressure pill. (felodipine) They used grapefuit juice to mask the taste of the ethanol.  Surprisingly, they saw a several fold increase in felodipine levels that could not be explained by their knowledge of ethanol.   They deduced that grapefruit juice played a roll.

         So why does grapefruit have this effect?  Many medications that we take need to be changed in the body before we get rid of them.  We call that change metabolism.  This metabolism occurs mostly in the liver or in the intestines by certain enzymes.   Grapefruit can block or inhibit certain enzymes in the intestines that are responsible for metabolizing some drugs.  The body then can't clear the medications and the levels in the body rise.  The significance of grapefruit interactions depends on how much the drug is metabolized and also drugs with a low therapeutic index (that is even small increases in blood levels can be toxic).  Generally speaking, drugs that are highly metabolized or have a low therapeutic index would pose the greatest risk.

         So which medications are affected?  Some common medications that can be affected include Amiodarone, Quinidine, Sertraline, Trazodone, Simvastatin, Lovastatin, Felodipine, Nifedipine, Triazolam, Carbamazepine are just a few examples.  There are many more and this is just a representation.   If you are concerned, you may wish to book a med-check appointment with your pharmacist to review all your medications.  Take care of yourselves and each other.  

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