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The carrot is a root vegetable, usually orange in colour, though purple, red, white, and yellow varieties exist. It has a crisp texture when fresh. The most commonly eaten part of a carrot is a taproot, although the greens are sometimes eaten as well. It is a domesticated form of the wild carrot Daucus carota, native to Europe and southwestern Asia. The domestic carrot has been selectively bred for its greatly enlarged and more palatable, less woody-textured edible taproot. The Food and Agriculture Organization of the United Nations (FAO) reports that world production of carrots and turnips (these plants are combined by the FAO for reporting purposes) for calendar year 2011 was almost 35.658 million tonnes. Almost half were grown in China. Carrots are widely used in many cuisines, especially in the preparation of salads, and carrot salads are a tradition in many regional cuisines.
Most carrot cultivars are about 88% water, 7% sugar, 1% protein, 1% fibre, 1% ash, and 0.2% fat. The fibre comprises mostly cellulose, with smaller proportions of hemicellulose and lignin. Carrots contain almost no starch. Free sugars in carrot include sucrose, glucose, xylose and fructose. Nitrite and nitrate contents are about 40 and 0.41 milligrams per 100 grams (fresh), respectively. Most of the taste of the vegetable is due to glutamic acid and other free amino acids. Other acids present in trace amounts include succinic acid, α-ketoglutaric acid, lactic acid and glycolic acid; the major phenolic acid is caffeic acid.
The carrot gets its characteristic and bright orange colour from β-carotene, and lesser amounts of α-carotene and γ-carotene. α and β-carotenes are partly metabolised into vitamin A in humans. β-carotene is the predominant carotenoid, although there are lesser amounts of α-carotene and γ-carotene. There are typically between 6000 and 54,000 micrograms of carotenoids per 100 grams of carrot root. Carrot extracts are used by poultry producers to improve animal skin and alter the colour of egg yolk. Massive overconsumption of carrots can cause carotenosis, a benign condition in which the skin turns orange. Carrots are also rich in antioxidants and minerals. Ethnomedically, the roots are used to as an emmenagogue (to increase blood flow in the pelvic area and uterus), a carminative (to reduce flatulence), to treat digestive problems, intestinal parasites, and tonsillitis or constipation.
Lack of vitamin A can cause poor vision, including night vision, and these can be restored by adding vitamin A to the diet. An urban legend states that eating large quantities of carrots will allow one to see in the dark. This myth developed from stories about British gunners in World War II, who were able to shoot down German planes at night. The rumour arose during the Battle of Britain when the RAF circulated a story about their pilots' carrot consumption in an attempt to cover up the discovery and effective use of radar technologies in engaging enemy planes, as well as the use of red light (which does not destroy night vision) in aircraft instruments. It reinforced existing German beliefs, and helped to encourage Britons who were trying to improve their night vision during the blackout to grow and eat the vegetable, which was not rationed like most other foodstuffs. A "Dr. Carrot" advertising campaign encouraged its consumption.