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Onion nutrition facts

Can you imagine a recipe without the onion in it? This wonderful bulb-vegetable, one of the oldest edible food ingredient 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 used in traditional medicines since ancient times for its health promoting and curative properties.

Botanically, onions belong to the Alliaceae family, in the genus, Allium and known scientifically as: Allium cepa.



spanish onion white variety onion oriental onion
Spanish or red onion. White variety. Oriental type.


Onion is a small herb plant that grows to about 2 feet tall. Its underground globular bulb is actually a stem which consists of modified leaves arranged in whorls. There are many cultivar varieties of onions grown around the world. On an average, its crop takes about three to four months from seedlings to harvest. Top greens or scallions and flower heads are also eaten all around the world.

Sharp, pungent smell of onion is due to its sulfur compound, allyl propyl disulphide. Spanish red onions generally possess less of this compound and therefore mild flavored than white or brown varieties. This characteristic of Spanish variety would makes them ideal for use in raw salads.

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


Health benefits of Onions

  • Onions are very low in calories and fats. 100 grams carry just 40 calories. However, rich in soluble dietary fiber.

  • Phyto-chemical compounds allium and Allyl disulphide in the onions convert into allicin by enzymatic reaction when its modified leaves are distorted (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.

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

  • Onions are rich source of chromium, a trace mineral that helps tissue cells respond appropriately to insulin levels in the blood. It 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 antioxidant vitamin, vitamin-C and mineral manganese. Manganese is required as a 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 can be readily available during all the seasons. Depending on the variety, they can be sharp, spicy, tangy and pungent or mild and sweet. In the stores, they can be available in fresh, frozen, canned, pickled, powdered, and dehydrated forms.

While buying, look for fresh ones that are clean, uniform, well-developed without having opening at the neck and feature crispy, and dry outer layers. 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 an indicators 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 take them out from the refrigerator since they tend to spoil if kept at room temperature for some time.


Preparation and serving methods

Trim either ends using a sharp knife. Then peel 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.

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

Here are some serving tips:

  • They can be used either 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, dips, sauces, etc., everyday.

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

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

  • Onions and shallots are some of common ingredients used extensively in pickling.


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), converts into sulfuric acid. Allyl sulphide is concentrated more at the ends, especially at its root end. Its effect can be minimized by immersing the trimmed bulb in cold water for a 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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Further resources:

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

3. USDA National Nutrient database.


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