The grapefruit (Citrus × paradisi), is a subtropical citrus tree known for its bitter fruit, an 18th-century hybrid first bred in Barbados. When found, it was named the "forbidden fruit"; it has also been misidentified with the pomelo or shaddock (C. maxima), one of the parents of this hybrid, the other being sweet orange (C. × sinensis).

These evergreen trees usually grow to around 5–6 meters (16–20 ft) tall, although they can reach 13–15 meters (43–49 ft). The leaves are dark green, long (up to 150 mm, 6 inches) and thin. It produces 5 cm (2 in) white four-petaled flowers. The fruit is yellow-orange skinned and largely an oblate spheroid; it ranges in diameter from 10–15 cm. The flesh is segmented and acidic, varying in color depending on the cultivars, which include white, pink and red pulps of varying sweetness. The 1929 US Ruby Red (of the Redblush variety) has the first grapefruit patent.

The fruit has become popular since the late 19th century; before that it was only grown as an ornamental plant. The United States quickly became a major producer of the fruit, with groves in Florida, Texas, Arizona, and California. In Spanish, the fruit is known as toronja or pomelo.


One ancestor of the grapefruit was the Jamaican sweet orange (Citrus sinensis), itself an ancient hybrid of Asian origin; the other was the Indonesian pomelo (C. maxima). One story of the fruit's origins is that a certain "Captain Shaddock" brought pomelo seeds to Jamaica and bred the first fruit. But it probably originated as a naturally-occurring hybrid.

The hybrid fruit was documented in 1750 by a Welshman, Rev. Griffith Hughes, who described specimens from Barbados. Currently, the grapefruit is said to be one of the "Seven Wonders of Barbados." It was brought to Florida by Count Odette Philippe in 1823 in what is now known as Safety Harbor. Further crosses have produced the tangelo (1905), the Minneola tangelo (1931), and the oroblanco (sweetie)(1984). The sweetie has very small genetic and other differences from the pomelo.

The grapefruit was known as the shaddock or shattuck until the 19th century. Its current name alludes to clusters of the fruit on the tree, which often appear similar to grapes. Botanically, it was not distinguished from the pomelo until the 1830s, when it was given the name Citrus paradisi. Its true origins were not determined until the 1940s. This led to the official name being altered to Citrus × paradisi, the "×" identifying its hybrid origin.

An early pioneer in the American citrus industry was Kimball Chase Atwood, a wealthy entrepreneur who founded the Atwood Grapefruit Co. in the late 19th century. The Atwood Grove became the largest grapefruit grove in the world, with an annual production of 80,000 boxes of fruit. It was there that pink grapefruit was first discovered in 1906.

The 1929 Ruby Red patent was associated with real commercial success, which came after the discovery of a red grapefruit growing on a pink variety. Only with the introduction of the Ruby Red did the grapefruit transform into a real agricultural success. The Red grapefruit, starting with the Ruby Red, has even become a symbolic fruit of Texas, where white "inferior" grapefruit were eliminated and only red grapefruit were grown for decades. Using radiation to trigger mutations, new varieties were developed to retain the red tones which typically faded to pink, the Rio Red variety is the current (2007) Texas grapefruit with registered trademarks Rio Star and Ruby-Sweet, also sometimes promoted as "Reddest" and "Texas Choice".

The Florida Department of Citrus states "the primary varieties of Florida grapefruit are Ruby Red, Pink, Thompson, Marsh and Duncan. The fresh grapefruit season typically runs from October through June."

Colors and flavors

Grapefruit comes in many varieties, determinable by color, which is caused by the pigmentation of the fruit in respect of both its state of ripeness. The most popular varieties cultivated today are red, white, and pink hues, referring to the internal pulp color of the fruit. The family of flavors range from highly acidic and somewhat bitter to sweet and tart. Grapefruit mercaptan, a sulfur-containing terpene, is one of the substances which has a strong influence on the taste and odor of grapefruit, compared with other citrus fruits.

Drug interactions

Grapefruit can have a number of interactions with drugs, often increasing the effective potency of compounds. In the field of polyphenolic compounds, grapefruit contains the flavanone naringin, alongside the two furanocoumarins bergamottin and dihydroxybergamottin, which inhibit the protein isoform CYP3A4 predominately in the small intestine, but at higher doses, hepatic CYP3A4 inhibition is present as well. It is via inhibition of this enzyme that grapefruit increases the effects of a variety of drugs by increasing their bioavailability. The effect from Grapefruits became well-publicized after being responsible for a number of deaths due to overdosing on medication. In particular grapefruit and bitter oranges are known to interact with statins.

Grapefruit juice may be the first documented, but apple and orange juices have been also implicated in interfering with etoposide, a chemotherapy drug, some beta blocker drugs used to treat high blood pressure, and cyclosporine, taken by transplant patients to prevent rejection of their new organs.Some citrus-based carbonated beverages (e.g., "Sun Drop") also contain enough grapefruit juice to cause drug interactions, particularly in patients taking cyclosporine.

Unlike other fruits, grapefruit contains a large amount of naringin, and it can take up to 72 hours before the effects of the naringin on the CYP3A4 enzyme are seen. This is particularly problematic due to the fact that only 4 oz of grapefruit contain enough naringin to inhibit substrates of CYP3A4.

Nutritional properties

Grapefruit is an excellent source of many nutrients and phytochemicals that contribute to a healthy diet. Grapefruit is a good source of vitamin C, contains the fiber pectin, and the pink and red hues contain the beneficial antioxidant lycopene. Studies have shown grapefruit helps lower cholesterol, and there is evidence that the seeds have antioxidant properties. Grapefruit forms a core part of the "grapefruit diet", the theory being that the fruit's low glycemic index is able to help the body's metabolism burn fat.

Grapefruit seed extract (GSE) has been claimed to have strong antimicrobial properties against bacteria and fungi. However, no studies have demonstrated any efficacy by GSE as an antimicrobial for either bacteria or fungi. Additionally, although GSE is promoted as a highly effective plant-based preservative by some natural personal care manufacturers, studies have shown that the apparent antimicrobial activity associated with GSE preparations is merely due to contamination with synthetic preservatives.

Since grapefruit juice is known to inhibit enzymes necessary for the clearance of some drugs and hormones, some have hypothesized that grapefruit juice may play an indirect role in the development of hormone-dependent cancers. A 2007 study found a correlation between eating a quarter of grapefruit daily and a 30% increase in risk for breast cancer in post-menopausal women. The study points to the inhibition of CYP3A4 enzyme by grapefruit, which metabolizes estrogen. However, a 2008 study has shown that grapefruit consumption does not increase breast cancer risk and found a significant decrease in breast cancer risk with greater intake of grapefruit in women who never used hormone therapy.

Grapefruit contains large quantities of a simple polyamine called spermidine, which may be related to aging. It is known to be necessary for cell growth and maturation, and as cells age their level of spermidine is known to fall. Scientists have shown that feeding spermidine to worms, fruit flies and yeast significantly prolongs their lifespan. In addition, adding spermidine to the diet of mice decreased molecular markers of aging, and when human immune cells were cultured in a medium containing spermidine, they also lived longer.

Grapefruit sweets

In Costa Rica, especially in Atenas, grapefruits are often cooked to remove their sourness, rendering them as sweets; they are also stuffed with dulce de leche, resulting in a dessert called toronja rellena (stuffed grapefruit).

Other uses
Grapefruit peel oil is used in aromatherapy and it is historically known for its aroma.
Grapefruit has also been investigated in cancer medicine pharmacodynamics. Its inhibiting effect on the metabolism of some drugs may allow smaller doses to be used, which can help to reduce costs.


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