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.
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 3.57 mg of iron , whereas a 100 g (3.5 oz) ground hamburger patty contains 2.49 mg. 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.
Production, marketing, and storage
Fresh spinach is sold loose, bunched, or packaged fresh in bags.
Some packaged spinach is exposed to radiation to kill any harmful bacteria.
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.
In popular culture
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 in ancient Persia (modern Iran and neighboring countries).
- It is not known by whom, or when, spinach was introduced to India.
- The plant was subsequently introduced to ancient China, where it was known as "Persian vegetable" (bōsī cài; 波斯菜; present:菠菜). The earliest available record of the spinach plant was recorded in Chinese, stating it was introduced into China via Nepal (probably in 647 AD).
- In AD 827, the Saracens introduced spinach to Sicily.
- The first written evidence of spinach in the Mediterranean was recorded in three 10th-century works: the medical work by al-Rāzī (known as Rhazes in the West) and in two agricultural treatises, one by Ibn Waḥshīyah and the other by Qusṭus al-Rūmī. Spinach became a popular vegetable in the Arab Mediterranean and arrived in Spain by the latter part of the 12th century, where it was called raʼīs al-buqūl, 'the chieftain of leafy greens'. Spinach was also the subject of a special treatise in the 11th century by Ibn Ḥajjāj.
- The prickly-seeded form of spinach was known in Germany by no later than the 13th century, though the smooth-seeded form was not described until 1552.
- Spinach first appeared in England and France in the 14th century, probably via Spain, and it gained quick popularity because it appeared in early spring, when other vegetables were scarce and when Lenten dietary restrictions discouraged consumption of other foods. Spinach is mentioned in the first known English cookbook, the Forme of Cury (1390), where it is referred to as 'spinnedge' and/or 'spynoches'. Smooth-seeded spinach was described in 1552.
- During World War I, wine fortified with spinach juice, which contains large quantities of vitamin K, was given to French soldiers afflicted with hemorrhage in hopes of ameliorating their condition.