December 7


Healthy grapefruit can be a recipe for medication modification side effects

By campuschiropractic

December 7, 2014

Healthy grapefruit can be a recipe for medication modification side effects

As you may have read in our recent post on the wellness fruit Pomegranate, there are some foods that don’t mix so well with some medications. Grapefruit is also one of these foods.


The grapefruit was originally bred in the 18th century as a cross between a pomelo and an orange. They were called grapefruits because they grew in clusters like grapes, unlike other citrus fruits. The range in both colour and flavour from white or yellow to red or pink and from highly acidic to very sweet and sugary.

Grapefruit are high in fibre, vitamin C, vitamin A and also have calcium and magnesium. They also contain small amounts of vitamin E, thiamin, riboflavin, niacin, folate, pantothenic acid, potassium, phosphorus, manganese, zinc and copper. Not only are they a great sourceof vitamins and minerals, but they also pack a powerful antioxidant punch with lycopene and beta-carotene along with the phytonutrients limonoids and naringenin.

They have been touted as supporting the immune system, promoting weight loss, lowering risk of stroke in women, and lowering risks of high blood pressure, ischemic heart disease and atherosclerosis. Grapefruit is said to help combat forms of free radicals known to cause cancer, improve digestion and promote health of the digestive tract and also of the skin and to be beneficial in asthma prevention. It is said to help the body in fighting various conditions like fatigue, fever, malaria, diabetes, constipation, indigestion, urinary problems, excess acidity and many more.

Like the pomegranate, the grapefruit seems to be so full of benefits and nutritional goodies that you might start to wonder if you shouldn’t start making it a regular part of your diet too. However, if you are taking certain medications, please be careful and check with your doctor and your chemist before embarking on a new diet regime.

What is the Effect of Grapefruit and Grapefruit Juice?

The difficulty with combining grapefruit, or even grapefruit juice with these medications is that it can increase the potency to potentially dangerous levels. There are usually enzymes in the wall of the small intestine that destroy elements of the medications and prevents them being absorbed into the body. This means that we actually absorb smaller amounts of the drug than we consume. Grapefruit blocks these enzymes, meaning we absorb a greater amount of the active ingredient than the dose is intended, and the blood levels of these medications increase. This can lead to toxic side effects.

With some drugs, just one serving of grapefruit can make it seem like you have taken numerous doses of the drug. For example, simvastatin, when taken with about a 7-ounce glass of grapefruit juice once a day for three days, produced a 330% greater concentration of the drug compared to taking it with water. This can cause life-threatening muscle damage called rhabdomyolysis.

Grapefruit are not the only fruit that can have a therapeutic interaction with pharmaceutical drugs. Other citrus fruits such as Seville oranges (often used in marmalade), limes, and pomelos also contain the active ingredients (furanocoumarins), but have not been as widely studied. Pomegranates have also been found to have an effect on certain medications. Read more on our Pomegranate blog.

So if you are fortunate enough not to need any ongoing medications, consider eating some grapefruit for your health and wellbeing. However, if you are taking a regular prescription medication then consult with your pharmacist and doctor to make sure it is safe for you to do so, and be aware that some fruit drinks and other processed foods can contain hidden grapefruit.


Mayo Clin Proc. 2000;75:933-9

Stump, A., Mayo, T., Blum, A.; "Management of Grapefruit-Drug Interactions." American Family Physician, August 15, 2006.

Shimomura, S. Wanwimolruk, S. Chen, J. "Drug Interactions with Grapefruit Juice: An Evidence-based Overview." Pharmacy Times, Accreditation Council for Pharmacy Eduction.


About the author

Campus Chiropractic & Wellness is as natural health clinic on the campus of the University of Sydney. The main services are chiropractic & remedial massage. Its current location was established in 2011 after Dr Jeremy Hammond, chiropractor, had already provided chiropractic on campus for 11 years.

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