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Onion nutrition facts

Can you imagine a recipe without the Onions? This wonderful bulb vegetable, one of the oldest edible source known to humankind, is found in a bewildering array of recipes and preparations, be it your favorite salad, or mouth-watering gravy or curries. It has also been in used in traditional medicines since ancient times for its health promoting and curative properties.

Botanically, the vegetable belongs to the Alliaceae family of the genus Allium and known scientifically as: Allium cepa.

Spanish or red onion.	White variety.	Oriental type.

The allium plant grows about 2 feet tall and bears an underground globular stem, which consists of modified leaves arranged in whorls. There are many cultivars onions grown around the world. The average crop takes about 3 to 4 months time. Top greens or scallions and flower heads are also eaten all around the world.

The sharp, pungent smell of onions is due to its sulfur compound allyl propyl disulphide. Spanish red onions are generally less strongly flavored than white or brown, which makes them ideal to use raw in salads.

Shallot (Allium cepa L. var. aggregatum) is a variety of the onion that produces a cluster of small-elongated bulbs from a single planted bulb. Shallots are relatively smaller and tastes sweeter than onions.

Health benefits of Onions

• Onions are very low in calories (just 40 cal per 100 g) and fats; but rich in soluble dietary fiber.

• Onion phyto-chemical compounds allium and Allyl disulphide convert to allicin by enzymatic reaction when the bulb disturbed (crushing, cutting etc). Studies have shown that these compounds have anti-mutagenic (protects from cancers) and anti-diabetic properties (helps lower blood sugar levels in diabetics).

• Laboratory studies show that allicin reduces cholesterol production by inhibiting HMG-CoA reductase enzyme in the liver cells. Further, it also found to have anti-bacterial, anti-viral, and anti-fungal activities.

• Allicin also decreases blood vessel stiffness by release of nitric oxide (NO); thereby bring reduction in the total blood pressure. It also blocks platelet clot formation and has fibrinolytic action in the blood vessels which, helps decrease overall risk of coronary artery disease (CAD), peripheral vascular diseases (PVD), and stroke.

• They are rich source of chromium, the trace mineral that helps tissue cells respond appropriately to insulin levels in the blood; thus helps facilitate insulin action and control sugar levels in diabetes.

• They are also good source of antioxidant flavonoid quercetin, which is found to have anti-carcinogenic, anti-inflammatory, and anti-diabetic functions. 

• They are also good in anti-oxidant vitamin, vitamin-C and mineral manganese which is required as co-factor for anti-oxidant enzyme superoxide dismutase. In addition, isothiocyanate anti-oxidants in them help provide relief from cold and flu by exerting anti-inflammatory actions.

• Onions are also good in B-complex group of vitamins like pantothenic acid, pyridoxine, folates and thiamin. Pyridoxine or vitamin B-6 helps keep up GABA levels in the brain, which works against neurotic conditions.

Selection and storage

Raw onions are readily available during all the seasons. Depending on the variety, they can be sharp, spicy, tangy and pungent or mild and sweet. In the store, they are available in fresh, frozen, canned, pickled, powdered, and dehydrated forms.

While buying, look for fresh ones that are clean, well shaped, have no opening at the neck and feature crispy, and dry outer skins. Avoid those that show sprouting or have signs of black mold (a kind of fungal attack) as they indicate that the stock is old. In addition, poor quality bulbs often have soft spots, moisture at their neck, and dark patches, which may all be indications of decay.

At home, store them in cool dark place away from moisture and humid conditions where they keep fresh for several days. They can also keep well in the refrigerator; however, you should use them immediately once you remove from the refrigerator since they tend to spoil if they kept at room temperature for a while.

Preparation and serving methods

Trim the ends using sharp knife. Then peel the outer 2-3 layers of skin until you find fresh thick pinkish-white whorls. You can slice or cut them into fine cubes depending upon the recipe type. Top greens and flower heads are also edible. Spring onions or scallions are favored in fast food preparations.

Here are some serving tips:

Delicious pizza with cheese and black olive topping. Photo courtesy: The essential vegetarian cookbook.	Cheeseburger with lettuce, tomato and onion. Photo courtesy: Sharon

• They are being used, usually chopped or sliced, in almost every type of food, including fresh salads, or as a spicy garnish.

• In India and Pakistan, onions are one of the most sought after ingredients in cooking where they used in curries, stir-fries, soups, stuffing, pastes, sauces...etc on daily basis.

• They are one of the common ingredients in Chinese "chowmein" (a kind of recipe with chopped onions, scallions, cabbage, sweet bell peppers, chili and tomato sauce mixture.

• They are used extensively in Mediterranean and continental cooking in salads, cheese pizza, burger, soup, tart, rolls, stuffing...etc.

Safety profile

Raw onions can cause irritation to skin, mucus membranes and eyes. This is due to release of allyl sulphide gas while chopping or slicing them. The gas when mixed with moisture (water), convert to sulfuric acid. Allyl sulphide is concentrated more at the ends, especially at the root end. Its effect can be minimized by immersing the trimmed bulb in cold water for few minutes before you chop or slice it. (Disclaimer).

<<-Back to Vegetables from Onion. Please visit here for an impressive list of vegetables with complete illustrations of their nutrition facts and health benefits.

<<-Shallots,

<<-Leeks,

<<-Scallions (onion greens)

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• Research articles on nutrition.

1. Stanford School of Medicine Cancer information Page- Nutrition to Reduce Cancer Risk (Link opens in new window).
2. Onions- University of Illinois extension. (Link opens in new window).

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