Grapefruit

Efficacy-safety rating:

●●...Ethno or other evidence of efficacy.

Safety rating:

What is Grapefruit?

The grapefruit is a large, dimpled, round citrus fruit, measuring 3 to 6 inches in diameter. It descends from a cross between a pomelo (pummelo) or shaddock (C. grandis), a large Malaysian citrus, and a sweet orange. Others believe the grapefruit may have arisen as a mutation of another type of citrus tree. The fruit grows in clusters similar to grapes, and this may be the reason why the “grapefruit” was so named. The 2 main varieties of grapefruit include the Duncan (many seeds and good flavor) and the Marsh (seedless with less flavor). The pink varieties followed; the Foster (1907; seeded) and the Thompson (1913; seedless). The Ruby red-pulped grapefruit was developed in the late twenties in McAllen, Texas. Grapefruits can be considered a “New World” product, a species only a few hundred years old.

What is Grapefruit used for?

In 1310 B.C., Greek historian Theophrastus wrote of how Citron was thought to be an antidote to poison and how it also could “sweeten the breath.” Later, Pliny, a Roman naturalist, used the word “citrus” for the first time and labeled the fruit as a medicine. The grapefruit, then called “small shaddock,” first was mentioned by Griffith Hughes in 1750, as the “forbidden fruit” of Barbados. The name “grapefruit” was said to have been first used in Jamaica in 1814. In 1823, the grapefruit was introduced in Florida by a French count, Odette Phillippe, but did not begin to gain popularity until the end of the nineteenth century. In the 1930s, Hollywood's “Grapefruit Diet” came into vogue, including limitation of calorie intake to approximately 800 per day, and including grapefruit consumption at each meal. Weight can be lost on this diet, but any diet based primarily on one food is too restrictive to be healthy because too many important nutrients may be missing.

Nutrition studies have been performed that discovered grapefruit to be of value as a dietary supplement. Grapefruit is high in water and fiber. The whole fruit also is a good source of potassium, vitamin C, inositol, bioflavonoids, and pectin. However, the juice alone is not high in pectin. In addition, grapefruit has no fat and is low in calories and sodium. The pink variety contains beta-carotene. Folic acid also is present in grapefruit.

Grapefruit also has been used as a nutritional supplement for patients experiencing potassium loss. Grapefruit pectin may reduce cholesterol and promote regression of atherosclerosis. Other effects include possible anti-cancer effects. Research on the medicinal uses of grapefruit is limited.

What is the dosage of Grapefruit?

Grapefruit juice has been given in clinical studies from 1 to 9 glasses daily, or 240 mL of double-strength juice twice daily.

Is Grapefruit safe?

Contraindicated in patients taking medication which is metabolized by liver/cytochrome P450 3A4 (CYP3A4) enzyme system.

Generally recognized as safe when used as food. Safety and efficacy for dosages above those in foods are unproven and should be avoided.

Grapefruit juice increases intestinal cell wall metabolism (CYP3A4) of albendazole, amiodarone, benzodiazepines (ie, midazolam and triazolam), buspirone, calcium channel blockers (including amlodipine, diltiazem, felodipine, nicardipine, nifedipine, nimodipine, nisoldipine, and verapamil), carbamazepine, cisapride, clomipramine, cyclosporine, dextromethorphan, estrogens (eg, estrone and ethinyl estradiol), fluvoxamine, HMG-CoA reductase inhibitors (eg, atorvastatin, lovastatin, simvastatin but not pravastatin), losartan, macrolide antibiotics (eg, clarithromycin, erythromycin), pimozide, praziquantel, quinidine, saquinavir, and scopolamine. Plasma concentrations of digoxin and sildenafil may be increased; while plasma concentrations of amprenavir, etoposide, fexofenadine, and itraconazole may be decreased. Grapefruit juice appears to delay both the absorption of indinavir and the time to reach peak plasma concentrations of indinavir and quinidine. It would be prudent to advise patients to take these medications with a liquid other than grapefruit juice and to avoid grapefruit juice.

A case report exists about grapefruit juice-induced hypotension.

Grapefruit juice can create adverse effects by altering drugs metabolized by the CYP3A4 enzyme system (eg, some nonsedating antihistamines, benzodiazepines, selected calcium channel blockers, estrogens, quinidine, and cyclosporine).

References

Copyright © 2006 Wolters Kluwer Health

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