Medically reviewed on June 7, 2018
What is Grapefruit?
The grapefruit is a large, dimpled, round citrus fruit. It is likely to be a cross between a pomelo or shaddock (Citrus 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 for the name "grapefruit". Noteworthy cultivated varieties of grapefruit include: Duncan (white, seeded); Marsh (seedless); Foster (pink, seeded); Thompson (pink, seedless); and redblush (red, seedless).
What is it used for?
The grapefruit, then called "small shaddock," was first mentioned by Griffith Hughes (1707-1758), 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, the Hollywood Diet, which recommended limiting intake to 800 calories per day and included grapefruit consumption at each meal, became popular. Worldwide production of grapefruit in 2010 was approximately 5.5 million metric tons, and the juice of the fruit, including concentrate, accounts for approximately 42% of all United States-processed grapefruit products.
Clinical trials are generally lacking for therapeutic uses. Grapefruit or its juice have potential in influencing weight loss and promoting cholesterol reduction, and have demonstrated antibacterial activity in the urinary tract.
What is the recommended dosage?
Quality clinical trials upon which to base dose recommendations are limited. Improved lipid profiles were achieved with consumption of 1 grapefruit daily for 30 days. Grapefruit juice 8 oz, or half of a fresh grapefruit, 3 times a day before each meal for 12 weeks resulted in weight loss in a clinical trial evaluating the effect on metabolic syndrome.
None well defined. In patients with major heart muscle disorders, pink grapefruit should probably be avoided due to its ability to disturb normal heart rhythms. Regular grapefruit consumption can increase or decrease blood levels of several drugs.
GRAS (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 has been reported to interact with numerous drugs; however, case reports of significant interactions are rare. However, the potential for an interaction with grapefruit is possible.
Reports of adverse reactions to grapefruit consumption are limited to drug interactions. Case reports exist of allergy to pectin and pectin-induced asthma.
Toxicological studies on whole grapefruit are lacking. An analysis of 3 studies evaluating the association of grapefruit consumption and risk of breast cancer found no increased risk. The constituent d-limonene in grapefruit has GRAS status. Grapefruit seed extract has been shown to be toxic to human skin.