The grapefruit (Citrus × paradisi) is a subtropical citrus tree known for its relatively large, sour to semi-sweet, somewhat bitter fruit. The flesh of the fruit is segmented and varies in color from pale yellow to dark red. Grapefruits originated in Barbados in the 18th century. They are a citrus hybrid that was created through an accidental cross between the sweet orange (C. × sinensis) and the pomelo (C. maxima), both of which were introduced to the Caribbean from Asia in the 17th century. It has also been called the 'forbidden fruit'. In the past it was called the pomelo, but that term is now mostly used as the common name for Citrus maxima. Grapefruit–drug interactions are common, as the juice contains furanocoumarins that interfere with the metabolism of many drugs. This can prolong and intensify the effects of those drugs, leading to multiple side-effects such as abnormal heart rhythms, bleeding inside the stomach, low blood pressure, difficulty breathing, and dizziness.
Description
The evergreen grapefruit trees usually grow to around 4.5–6 m (15–20 ft) tall, although they may reach 13.7 m (45 ft). The leaves are up to 15 cm (6 in) long, thin, glossy, and dark green. They produce 5 cm (2 in) white flowers with four or five petals. The fruit is yellow-orange skinned and generally an oblate spheroid in shape; it ranges in diameter from 10 to 15 cm (4 to 6 in). Its flesh is segmented and acidic, varying in color depending on the cultivars, which include white, pink, and red pulps of varying sweetness (generally, the redder varieties are the sweetest).
Varieties
White grapefruit varieties include Camulos, Cecily, Duncan, Frost Marsh, Genetic Dwarf Marsh, Hall, Jochimsen, Marsh seedy, Nicholson navel, Perlis, Reed Marsh, Tetraploid, Warren Marsh, and Whitney Marsh. Red or pink grapefruit varieties include Flame, Foster Pink, Henderson Ruby, Hudson Foster, Marsh Pink, Ray Ruby, Redblush, Rio Red, Shambar, and Star Ruby. The 1929 'Ruby Red' (or 'Redblush') patent was associated with real commercial success, which came after the discovery of a red grapefruit growing on a pink variety. The Texas Legislature designated this variety the official "State Fruit of Texas" in 1993. Using radiation to trigger mutations, new varieties were developed to retain the red tones that typically faded to pink. The 'Rio Red' variety is a 1984 registered Texas grapefruit with registered trademarks Rio Star and Ruby-Sweet, also sometimes promoted as Reddest and Texas Choice. The 'Rio Red' is a mutation-bred variety that was developed by treatment of bud sticks with thermal neutrons. Its improved attributes of mutant variety are fruit and juice color, deeper red, and wide adaptation. The 'Star Ruby' is the darkest of the red varieties. Developed from an irradiated 'Hudson' grapefruit ('Hudson' being a limb sport of 'Foster', itself a limb sport of the 'Walters'), it has found limited commercial success because it is more difficult to grow than other varieties.
As food
Nutrition
Raw white grapefruit is 90% water, 8% carbohydrates and 1% protein, with negligible fat (table). In a reference amount of 100 grams (3+1⁄2 ounces), raw grapefruit provides 138 kilojoules (33 kilocalories) of food energy and is a rich source of vitamin C (37% of the Daily Value), with no other micronutrients in significant amounts (table).
Culinary Like other citrus fruits, grapefruits are sour because of their citric acid content; grapefruit juice contains about half the citric acid content of lemon juice, and nearly 50% more than orange juice. In Costa Rica, especially in Atenas, grapefruit are often cooked with sugar to balance their sourness, rendering them as sweets; or they are stuffed with dulce de leche as a dessert. In Haiti, grapefruit is used primarily for its juice (French: jus de Chadèque), but also is used to make jam (French: confiture de Chadèque). Grapefruit varieties are differentiated by the flesh color of fruit they produce. Common varieties are yellow and pink pulp colors. Flavors range from highly acidic and somewhat sour to sweet and tart, resulting from composition of sugars (mainly sucrose), organic acids (mainly citric acid), and monoterpenes and sesquiterpenes providing aromas. Grapefruit mercaptan, a sulfur-containing terpene, is one of the aroma compounds influencing the taste and odor of grapefruit, compared with other citrus fruits.
Drug interactions
Grapefruit and grapefruit juice interact with many drugs, resulting in numerous adverse effects including bone marrow suppression, nephrotoxicity, abnormal heart rhythm, rhabdomyolysis, hypotension, gastrointestinal bleeding, dizziness, and respiratory depression, according to the drug involved. One interaction occurs from grapefruit furanocoumarins, such as bergamottin and 6',7'-dihydroxybergamottin, which occur in both flesh and peel. Furanocoumarins inhibit the CYP3A4 enzyme (among others from the cytochrome P450 enzyme family responsible for metabolizing 90% of drugs). The action of the CYP3A4 enzyme itself is to metabolize many medications. If a drug's breakdown for removal is lessened, then the level of that drug in the blood may become and remain high, leading to adverse effects. On the other hand, some drugs must be metabolized to become active, and inhibiting CYP3A4 may lead to reduced drug effects. Another effect is that grapefruit compounds may inhibit the absorption of drugs in the intestine. If a drug is not absorbed, then not enough of it is in the blood to have a therapeutic effect. Each affected drug has either a specific increase of effect or decrease. One whole grapefruit or a glass of 200 mL (7 US fl oz) of grapefruit juice is enough to cause significant increases in drug exposure and harm. This especially affects drugs with low bioavailability due to high first pass metabolism. Typically, drugs that are incompatible with grapefruit are marked as such on the container or package insert.
Production
In 2023, world production of grapefruits (combined with pomelos) was 9.93 million tonnes, led by China with 52% of the total and Vietnam as a secondary producer (table).
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