Grapefruit juice

Grapefruit juice is the fruit juice from grapefruits. It is rich with Vitamin C and ranges from sweet-tart to very sour. Variations include white grapefruit, pink grapefruit and ruby red grapefruit juice.The World's Healthiest Foods; Grapefruit. "The George Mateljan Foundation." [http://www.whfoods.com/genpage.php?tname=foodspice&dbid=25 Article] ] Fellers PJ, Nikdel S, Lee HS. Nutrient content and nutrition labeling of several processed Florida citrus juice products. "J Am Diet Assoc." 1990 Aug;90(8):1079-84. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2380455 Abstract] ]

Drug interactions

Grapefruit juice, and grapefruit in general, is a potent inhibitor of the intestinal cytochrome P450 enzyme CYP3A4, which can impact the metabolism of a variety of drugs, increasing their bioavailability when administered orally. He K; Iyer KR; Hayes RN; Sinz MW; Woolf TF; Hollenberg PF. Inactivation of cytochrome P450 3A4 by bergamottin, a component of grapefruit juice. "Chem Res Toxicol." 1998 Apr;11(4):252-9. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9548795&dopt=Abstract Abstract] ] Bailey DG, Malcolm J, Arnold O, Spence JD. Grapefruit juice-drug interactions. Br J "Clin Pharmacol." 1998 Aug;46(2):101-10. Comment in: Br J "Clin Pharmacol." 2001 Aug;52(2):216-7. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9723817 Abstract] ] Garg SK, Kumar N, Bhargava VK, Prabhakar SK. Effect of grapefruit juice on carbamazepine bioavailability in patients with epilepsy. "Clin Pharmacol Ther." 1998 Sep;64(3):286-8. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9757152 Abstract] ] Bailey DG, Dresser GK. Interactions between grapefruit juice and cardiovascular drugs. "Am J Cardiovasc Drugs." 2004;4(5):281-97. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15449971 Abstract] ] Bressler R. Grapefruit juice and drug interactions. Exploring mechanisms of this interaction and potential toxicity for certain drugs. "Geriatrics." 2006 Nov;61(11):12-8. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=17112309 Abstract] ] In some cases, this can lead to a fatal interaction with drugs like astemizole or terfenadine. The effect of grapefruit juice with regard to drug absorption was originally discovered in 1989. However, the effect became well-publicized after being responsible for a number of deaths due to overdosing on medication.Bakalar, Nicholas. Experts Reveal the Secret Powers of Grapefruit Juice. "New York Times." Published: March 21, 2006. [http://www.nytimes.com/2006/03/21/health/21grap.html?ex=1300597200&en=61e834f36b9afac9&ei=5090&partner=rssuserland&emc=rss Article] ]

Recently some researchers have shown that furanocoumarins rather than flavonoids are the ingredients causing the various drug interactions. http://www.hon.ch/News/HSN/532584.html cite news
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Drugs that may be affected include midazolam, ciclosporin, lovastatin, methadone, dextromethorphan, simvastatin, pravastatin, felodipine, sildenafil (Viagra) and caffeine, as well as a number of antihistamines including astemizole and terfenadine. [cite web
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An easy way to tell if a medication may be affected by grapefruit juice is by researching whether another known CYP3A4 inhibitor drug is already contraindicated with the drug in question. Examples of such known CYP3A4 inhibitors include cisapride (Propulsid), erythromycin, itraconazole (Sporanox), ketoconazole (Nizoral), and mibefradil (Posicor)Fact|date=September 2008.

The flavonoid existing in highest concentration in grapefruit juice is naringin, which in humans is metabolised to naringenin. Other flavonoids exist in grapefruit juice in lower concentrations as well. Orange juice does not contain naringin in as high a concentration, instead containing hesperetin. It is sometimes recommended as a substitute. Juice of limes and Seville oranges can also inhibit drug metabolism, however, as can apple juice with some drugs.

Breast cancer link

A recent study published in the July 2007 edition of the British Journal of Cancer reported that eating grapefruit every day could raise the risk of developing breast cancer by almost a third. The Study found that in the test subjects, 50,000 post-menopausal women, eating just a quarter of a grapefruit daily raised the risk by up to 30%. It is believed that the fruit boosts the levels of estrogen, which in turn increases the risk of developing the disease. [ [http://news.bbc.co.uk/2/hi/health/6900482.stm BBC NEWS | Health | Grapefruit link to breast cancer ] ]

See also

* Grapefruit spoon

References