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SPINACH
Spinach, raw
Nutritional value per 100 g |
| Energy 20 kcal 100 kJ |
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Percentages are relative to US RDI
values for adults.
Source: USDA Nutrient database |
Spinach (Spinacia oleracea) is a flowering plant in the family Amaranthaceae, native to central and southwestern Asia. It is an annual plant (rarely biennial), which grows to a height of up to one metre. The leaves are alternate, simple, ovate to triangular-based, very variable in size from about 3-30 cm long and 1-15 cm 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 diameter, maturing into a small hard dry lumpy fruit cluster 5-10 mm across containing several seeds.
Cultivation and uses
Spinach is an important leaf vegetable, now grown throughout the temperate regions of the world. It is most productive in cool seasons and climates, since heat will cause the spinach to go to seed too early. When cooked, its volume is decreased by three quarters.
History
Spinach was first cultivated in southwestern Asia, perhaps in Persia. The word itself is derived from the Persian word اسفناج Esfenaj. The Chinese referred to it in 647 as 'the herb of Persia'.
It arrived in North Africa through Syria and Arabia. In 1100, the Moors introduced it to Spain. Over the next century, prickly seeded spinach spread throughout Europe, being grown primarily in monastery gardens. A cookbook dating from 1390, belonging to King Richard II, contains spinach recipes. Smooth seeded spinach seems to have spread through Europe slightly later. Its use in England was first documented in 1551.
Nutrition
In popular folklore, spinach is a rich source of iron. In reality, a 60 gram serving of boiled spinach contains around 1.9 mg of iron. A good many green vegetables contain less than 1 mg of iron for an equivalent serving. Hence spinach does contain a relatively high level of iron for a vegetable, but its consumption does not have special health connotations as folklore might suggest.
Ultimately, the bioavailability of iron is dependent on its absorption. This is influenced by a number of factors. Iron enters the body in two forms: nonheme iron and heme iron. All of the iron in grains and vegetables, and about three fifths of the iron in animal food sources (meats), is nonheme iron. The much smaller remaining portion from meats is heme iron (Williams, 1993).
This larger portion of dietary iron (nonheme) is absorbed slowly in its many food sources, including spinach. This absorption may vary widely depending on the presence of binders such as fiber or enhancers, such as vitamin C. Therefore, the body's absorption of non-heme iron can be improved by consuming foods that are rich in vitamin C. However, spinach contains high levels of oxalate. Oxalates bind to iron to form ferrous oxalate and remove iron from the body. Therefore, a diet high in oxalate (or phosphate or phytate) leads to a decrease in iron absorption.
The myth about spinach and its high iron content may have first been propagated by Dr. E. von Wolf in 1870, because a misplaced decimal point in his publication led to an iron-content figure that was ten times too high. In 1937, German chemists reinvestigated this "miracle vegetable" and corrected the mistake. It was described by T.J. Hamblin in British Medical Journal, December 1981.
Spinach also has a high calcium content. The oxalate content in spinach binds with calcium decreasing its absorption. By way of comparison, the body can absorb about half of the calcium present in broccoli, yet only around 5% of the calcium in spinach. Oxalate is one of a number of factors that can contribute to gout and kidney stones. Equally or more notable factors contributing to calcium stones are: genetic tendency, high intake of animal protein, excess calcium intake, excess vitamin D, prolonged immobility, hyperparathyroidism, renal tubular acidosis, and excess dietary fiber (Williams, 1993).
Spinach still has a large nutritional value, especially when fresh, steamed, or quickly boiled. It is a rich source of Vitamin A, Vitamin C, Vitamin E and several vital antioxidants. Recently, opioid peptides called rubiscolins have also been found in spinach. It is a source of folic acid, and this vitamin was first purified from spinach. To benefit from the folate in spinach, it is better to steam it than to boil it. Boiling spinach for four minutes can halve the level of folate.
Types of spinach
A distinction can be made between older varieties of spinach and more modern varieties. Older varieties tend to run up to seed too quickly in warm conditions. Newer varieties tend to grow more rapidly but have less of an inclination to run up to seed. The older varieties have narrower leaves and tend to have a stonger (although more bitter) taste. Most newer varieties have broader leaves and round seeds.
There are 3 basic types of Spinach:
- Savoy has dark green, crinkly and curly leaves. It is the type sold in fresh bunches in most supermarkets. One heirloom variety of savoy is Bloomsdale. Bloomsdale is also somewhat bolt resistant.
- Flat/smooth leaf spinach has broad smooth leaves that are easier to clean than savoy. This type is often grown for canned and frozen spinach, as well as soups, baby foods, and processed foods.
- Semi-savoy is a hybrid variety. It has slightly crinkled leaves. It has the same texture as savoy, but it is not as difficult to clean. It is grown for both fresh market and processing. Five Star is a widely grown variety and has good resistance to running up to seed.
Rosemary Stanton, in her Complete Book of Food and Nutrition, notes that silverbeet (or chard), is commonly referred to as spinach, particularly in Australia and New Zealand. Hence, there may be some popular confusion between the two vegetables.
Purchasing
Spinach can be bought loosely or in prepackaged bags. You can get better quality when you buy loosely, because you can examine all the leaves. When examining the leaves, pick the ones that are smaller and have a good green color to them. Leaves that are crisp and spongy are of good quality. Do not pick leaves that are wilting, brown or yellow. Fresh spinach should smell sweet, never sour or musty. Look for stems that are fairly thin and coarse. Thick stems indicate overgrown spinach, which may be leathery and bitter. If only bagged spinach is available where you shop, check whether the contents seem resilient when you squeeze the bag.
Storage
Spinach loses much of its nutritional value with storage of more than a few days. While refrigeration slows this effect to about eight days, spinach will lose most of its folate and carotenoid content. This is worth considering when purchasing spinach out of season. If the product has been "in transit" (picked, cleaned, shipped and shelved) for more than one or two days it will need to be used almost immediately to have much nutritional benefit. This is in spite of the taste and appearance of the plant which may still seem fine.
Fresh spinach should be cleaned thoroughly and then can be stored loosely in an unsealed bag in the crisper tray of the refrigerator for a few days. Even at 4°C, spinach loses much of its nutritional value by eight days so for longer storage it should be fresh frozen, cooked and frozen or canned. Storage in the freezer can be for up to eight months.
It is sometimes discouraged to reheat spinach leftovers since poisonous compounds would be formed during this process. What's behind this advice is that certain bacteria can grow on prepared nitrate-rich food, such as spinach and many other green vegetables. These bacteria can convert the nitrates into nitrites, which can be harmful to infants younger than six months. Also, during the reheating, the nitrate-converting enzymes produced by the bacteriae can convert even more at elevated temperatures during the second heating. For older children and adults, small concentrations of nitrites are harmless, although formation of nitrosamine compounds from the nitrites could be of concern for adults as well. [1]
Spinach in popular culture
- Popeye the Sailor has a strong affinity for spinach, and he becomes much stronger after consuming it.
Other species called spinach
The name spinach has been applied to a number of leaf vegetables, both related and unrelated to spinach:
- Related species
- Chard (Beta vulgaris, Amaranthaceae), also known as spinach beet or perpetual spinach.
- Orache (Atriplex species, Amaranthaceae), also called "French spinach" or "mountain spinach".
- Good King Henry (Chenopodium bonus-henricus, Amaranthaceae) and other Chenopodium species, also called "Lincolnshire spinach".
In Indonesia, the word bayam is applied both to certain species of amaranth commonly eaten as a leafy vegetable, and to spinach, which is rarely seen, only in certain supermarkets but well known from Popeye cartoons.
- Unrelated species
References and external links
- D. Maue, S. Walia, S. Shore, M. Parkash, S. K. Walia, S. K. Walia (2005). "Prevalence of Multiple Antibiotic Resistant Bacteria in Ready-to-Eat Bagged Salads". American Society for Microbiology meeting. June 5-9, Atlanta. Abstract
- Overview of Spinach from Innvista
- Rogers, Jo. What Food is That?: and how healthy is it?. The Rocks, Sydney, NSW: Lansdowne Publishing Pty Ltd, 1990. ISBN 1863028234.
- Cardwell, Glenn. Spinach is a Good Source of What?. The Skeptic. Volume 25, No 2, Winter 2005. Pp 31-33. ISSN 0726-9897
- Blazey, Clive. The Australian Vegetable Garden: What's new is old. Sydney, NSW: New Holland Publishers, 1999. ISBN 1864365382
- Stanton, Rosemary. Complete Book of Food and Nutrition. Australia, Simon & Schuster, Revised Edition, 1995. ISBN 0731805380
- Health Benefits of Spinach
- Williams, S.R. (1993) Nutrition and Diet Therapy 7th ed. Mosby: St. Loius, MO
- The nutritional benefits of spinach were discussed in detail in the Skeptic magazine, (Winter 2005).
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