|Spinach plant with flowers|
Spinach (Spinacia oleracea) is a leafy green flowering plant native to central and western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common edible vegetable consumed either fresh, or after storage using preservation techniques by canning, freezing, or dehydration. It may be eaten cooked or raw, and the taste differs considerably; the high oxalate content may be reduced by steaming.
It is an annual plant (rarely biennial), growing as tall as 30 cm (1 ft). Spinach may overwinter in temperate regions. The leaves are alternate, simple, ovate to triangular, and very variable in size: 2-30 cm (1-12 in) long and 1-15 cm (0.4-5.9 in) broad, with larger leaves at the base of the plant and small leaves higher on the flowering stem. The flowers are inconspicuous, yellow-green, 3-4 mm (0.1-0.2 in) in diameter, and mature into a small, hard, dry, lumpy fruit cluster 5-10 mm (0.2-0.4 in) across containing several seeds.
Common spinach, S. oleracea, was long considered to be in the family Chenopodiaceae, but in 2003 that family was merged into the Amaranthaceae in the order Caryophyllales. Within the family Amaranthaceae sensu lato, Spinach belongs to the subfamily Chenopodioideae.
Spinach is an annual plant (rarely biennial) growing as tall as 30 cm (1 ft). Spinach may overwinter in temperate regions. The leaves are alternate, simple, ovate to triangular, and very variable in size: 2-30 cm (1-12 in) long and 1-15 cm (0.4-5.9 in) broad, with larger leaves at the base of the plant and small leaves higher on the flowering stem. The flowers are inconspicuous, yellow-green, 3-4 mm (0.1-0.2 in) in diameter, and mature into a small, hard, dry, lumpy fruit cluster 5-10 mm (0.2-0.4 in) across containing several seeds.
Raw spinach is 91% water, 4% carbohydrates, 3% protein, and contains negligible fat. In a 100 g (3.5 oz) serving providing only 23 calories, spinach has a high nutritional value, especially when fresh, frozen, steamed, or quickly boiled. It is a rich source (20% or more of the Daily Value, DV) of vitamin A, vitamin C, vitamin K, magnesium, manganese, iron and folate. Spinach is a good source (10-19% of DV) of the B vitamins riboflavin and vitamin B6, vitamin E, calcium, potassium, and dietary fiber. Although spinach is touted as being high in iron and calcium content, and is often served and consumed in its raw form, raw spinach contains high levels of oxalates, which block absorption of calcium and iron in the stomach and small intestine. Spinach cooked in several changes of water has much lower levels of oxalates and is better digested and its nutrients absorbed more completely.
Spinach, along with other green, leafy vegetables, contains an appreciable amount of iron attaining 21% of the Daily Value in a 100 g (3.5 oz) amount of raw spinach. For example, the United States Department of Agriculture states that a 100 g (3.5 oz) serving of cooked spinach contains of iron , whereas a 100 g (3.5 oz) ground hamburger patty contains mg of iron.. However, spinach contains iron absorption-inhibiting substances, including high levels of oxalate, which can bind to the iron to form ferrous oxalate and render much of the iron in spinach unusable by the body. In addition to preventing absorption and use, high levels of oxalates remove iron from the body.
Spinach also has a moderate calcium content which can be affected by oxalates, decreasing its absorption. The calcium in spinach is among the least bioavailable of food calcium sources. By way of comparison, the human body can absorb about half of the calcium present in broccoli, yet only around 5% of the calcium in spinach.
A quantity of 3.5 ounces of spinach contains over four times the recommended daily intake of vitamin K. For this reason, individuals taking the anticoagulant warfarin – which acts by inhibiting vitamin K – are instructed to minimize consumption of spinach (as well as other dark green leafy vegetables) to avoid blunting the effect of warfarin.
(millions of tonnes)
|Source: UN Food & Agriculture Organization, Statistics Division (FAOSTAT)|
Fresh spinach is sold loose, bunched, or packaged fresh in bags. Fresh spinach loses much of its nutritional value with storage of more than a few days. Fresh spinach is packaged in air, or in nitrogen gas to extend shelf life. While refrigeration slows this effect to about eight days, fresh spinach loses most of its folate and carotenoid content over this period of time. For longer storage, it is canned, or blanched or cooked and frozen. Frozen spinach can be stored for up to eight months.
Some packaged spinach is exposed to radiation to kill any harmful bacteria. The Food and Drug Administration approves of irradiation of spinach leaves up to 4.0 kilograys; however, using radiation to sanitize spinach is of concern because it may deplete the leaves of their nutritional value.
Researchers at the Agricultural Research Service experimentally tested the concentrations of vitamins C, E, K, B9, and four carotenoids in packaged spinach following irradiation. They found with increasing level of irradiation, four nutrients showed little or no change. Those nutrients include vitamins B9, E, K, and the carotenoid neoxanthin. This study showed the irradiation of packaged spinach to have little or no change to the nutritional value of the crop, and the health benefits of irradiating packed spinach to reduce harmful bacteria seem to outweigh the loss of nutrients.
Spinach may be high in cadmium contamination depending on the soil and location where the spinach is grown.
The comics and cartoon character Popeye the Sailor Man has been portrayed since 1931 as having a strong affinity for spinach, particularly the canned variety. He becomes physically stronger after consuming it.
Spinach is thought to have originated about 2000 years ago in ancient Persia from which it was introduced to India and ancient China via Nepal in 647 AD as the "Persian vegetable". The first written evidence of spinach in the Mediterranean was recorded in the 10th century, with its food uses occurring in Spain by the 12th century.
Spinach first appeared in England and France in the 14th century, probably via Spain, and gained common use because it appeared in early spring when fresh local vegetables were not available. Spinach is mentioned in the first known English cookbook, the Forme of Cury (1390), where it is referred to as 'spinnedge' and/or 'spynoches'. During World War I, wine fortified with spinach juice – a rich source of vitamin K required for blood coagulation – was given to injured French soldiers with the intent to curtail their bleeding.