I received this recently from Dr Keith Scott-Mumby a Doctor and writer with some fascinating background and interests.
"One Lousy Grapefruit Could Kill You!
By Keith Scott-Mumby MD, MB ChB, PhD
Grapefruit poses a potentially lethal health risk to more and more patients taking prescription drugs. The fruit contains chemicals called furanocoumarins, which interfere with the cytochrome P-450 detox pathway enzymes. We need these enzymes to detox and eliminate all poisons but especially drugs. Adverse effects due to blocking that detox pathway can include acute kidney failure, respiratory failure, internal bleeding and sudden death.
All that, from eating a lousy grapefruit?
Yes. While it is well known that some patients should avoid grapefruit, or grapefruit juice, the list of drugs involved has risen sharply in recent years. More than 85 current drugs can interact with grapefruit, and of these 43 can have serious side effects, according to scientists writing in the Canadian Medical Association Journal [Bailey, D.G. Canadian Medical Association Journal, published online Nov. 26, 2012].
The important thing is to be savvy and know about this. You may know someone taking one or more meds, who likes to dive into citrus fruits. It's not just grapefruit; other citrus fruit can cause the problem, like limes and oranges (so, think marmalade). They also contain furanocoumarins, which act on an enzyme in the gut that normally somewhat de-activates the medication. This can effectively boost the blood levels of certain drugs, sometimes to dangerous levels.
A modest single helping of grapefruit can have an effect even if consumed hours before a drug is taken. Frequent exposure to grapefruit could make matters worse. Combining the cholesterol-lowering drug simvastatin with a 200-millilitre glass of grapefruit juice once a day (approximately 7 US fluid ounces) for three days more than trebled the concentration level of the statin.
Many furanocoumarins are toxic and are produced by plants as a defense mechanism against various types of predators ranging from insects to mammals.
They can also cause a sunlight-sensitive skin rash. Bergamottin is one of them; that's the main flavor in Earl Grey tea, though I've never heard of the tea causing reactions.
Of course the real problem is with the drugs, not the humble grapefruit. He was here first!
However, I noticed from the late 70s the citrus fruits are common food allergy offenders and they are on my elimination diet list of banned foods.
Check out my ground-breaking book "Diet Wise" for more (much more) on food interactions of the sort you wouldn't believe and you would never guess! Foods are NOT friendly on the whole...
FOOTNOTE: You'll hear me say a lot about the health benefits of fungi and mushrooms. Some of our edible mushrooms are kind to us and help us by mopping up furanocoumarins!
The fungi tested in the study I found were Morchella esculenta (common morel), Monascus purpureus (red rice yeast), Pleurotus sapidus (oyster mushroom) and Agaricus bisporus (common white table mushroom or button mushroom).
Eat lots of mushrooms; they taste great and do you good in more ways than just protecting you from grapefruit!
[SOURCE: J. Agric. Food Chem., 2008, 56 (24), pp 12064-12068 DOI: 10.1021/jf802713g]
Prof. "
