Onions
What would a kitchen be without the distinctively pungent smell and taste of onions filling out the flavors of almost every type of cuisine imaginable? Fortunately, yellow storage onions are available throughout the year but sweet varieties have a much more limited growing season and are available only a few months out of the year.
The word onion comes from the Latin word unio for "single," or "one," because the onion plant produces a single bulb, unlike its cousin, the garlic, that produces many small bulbs. The name also describes the union (also from unio) of the many separate, concentrically arranged layers of the onion.
This chart graphically details the %DV that a serving of Onions provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Onions can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Onions, featuring information over 80 nutrients, can be found under the Food Rating System Chart.
Blood Sugar-Lowering EffectsThe higher the intake of onion, the lower the level of glucose found during oral or intravenous glucose tolerance tests. Experimental and clinical evidence suggests that allyl propyl disulfide is responsible for this effect and lowers blood sugar levels by increasing the amount of free insulin available. Allyl propyl disulfide does this by competing with insulin, which is also a disulphide, to occupy the sites in the liver where insulin is inactivated. This results is an increase in the amount of insulin available to usher glucose into cells causing a lowering of blood sugar.
In addition, onions are a very good source of chromium, the mineral component in glucose tolerance factor, a molecule that helps cells respond appropriately to insulin. Clinical studies of diabetics have shown that chromium can decrease fasting blood glucose levels, improve glucose tolerance, lower insulin levels, and decrease total cholesterol and triglyceride levels, while increasing good HDL-cholesterol levels. Marginal chromium deficiency is common in the United States, not surprising since chromium levels are depleted by the consumption refined sugars and white flour products as well as the lack of exercise. One cup of raw onion contains over 20% of the Daily Value for this important trace mineral.
Cardiovascular BenefitsThe regular consumption of onions has, like garlic, been shown to lower high cholesterol levels and high blood pressure, both of which help prevent atherosclerosis and diabetic heart disease, and reduce the risk of heart attack or stroke. These beneficial effects are likely due to onions' sulfur compounds, its chromium and its vitamin B6, which helps prevent heart disease by lowering high homocysteine levels, another significant risk factor for heart attack and stroke.
Onions have been singled out as one of the small number of vegetables and fruits that contributed to the significant reduction in heart disease risk seen in a meta-analysis of seven prospective studies. Of the more than 100,000 individuals who participated in these studies, those who diets most frequently included onions, tea, apples and broccoli-the richest sources of flavonoids-gained a 20% reduction in their risk of heart disease.
Support Gastrointestinal HealthThe regular consumption of onions, as little as two or more times per week, is associated with a significantly reduced risk of developing colon cancer. Onions contain a number of flavonoids, the most studied of which, quercitin, has been shown to halt the growth of tumors in animals and to protect colon cells from the damaging effects of certain cancer-causing substances. Cooking meats with onions may help reduce the amount of carcinogens produced when meat is cooked using high heat methods.
Quercitin, an antioxidant in onions, and curcumin, a phytonutrient found in the curry spice turmeric, reduce both the size and number of precancerous lesions in the human intestinal tract, suggests research published in Clinical Gasteroenterology and Hepatology.
Five patients with an inherited form of precancerous polyps in the lower bowel known as familial adenomatous polyposis (FAP) were treated with regular doses of curcumin and quercetin over an average of six months. The average number of polyps dropped 60.4%, and the average size of the polyps that did develop dropped by 50.9%.
FAP runs in families and is characterized by the development of hundreds of polyps (colorectal adenomas) and, eventually, colon cancer. Recently, nonsteroidal anti-inflammatory drugs (NSAIDs such as aspirin, ibuprofen) have been used to treat some patients with this condition, but these drugs often produce significant side effects, including gastrointestinal ulcerations and bleeding, according to lead researcher Francis M. Giardiello, M.D., at the Division of Gastroenterology, Johns Hopkins University.
Previous observational studies in populations that consume large amounts of curry, as well as animal research, have strongly suggested that curcumin, one of the main ingredients in Asian curries, might be effective in preventing and/or treating cancer in the lower intestine. Similarly, quercetin, an anti-oxidant flavonoid found in a variety of foods including onions, green tea and red wine, has been shown to inhibit growth of colon cancer cell lines in humans and abnormal colorectal cells in animals.
In this study, a decrease in polyp number was observed in four of five patients at three months and four of four patients at six months.
Each patient received curcumin (480 mg) and quercetin (20 mg) orally 3 times a day for 6 months. Although the amount of quercetin was similar to what many people consume daily, the curcumin consumed was more than would be provided in a typical diet because turmeric only contains on average 3-5 % curcumin by weight. While simply consuming curry and onions may not have as dramatic an effect as was produced in this study, this research clearly demonstrates that liberal use of onions and turmeric and onions can play a protective role against the development of colorectal cancer.
Onion and Garlic Protective against Many CancersMaking onion and garlic a staple in your healthy way of eating may greatly lower your risk of several common cancers, suggests a large data set of case-control studies from Southern European populations (Galeone C, Pelucchi C et al, American Journal of Clinical Nutrition).
Study participants consuming the most onions showed an 84% reduced risk for cancer of the oral cavity and pharynx, 88% reduced risk for esophageal cancer, 56% reduced risk for colorectal cancer, 83% reduced risk for laryngeal cancer, 25% reduced risk for breast cancer, 73% reduced risk for ovarian cancer, 71% reduced risk for prostate cancer, and 38% reduced risk for renal cell cancer, compared to those eating the least onions. Similarly, those eating the most garlic had a 39% reduced risk for cancer of the oral cavity and pharynx, 57% reduced risk for esophageal cancer, 26% reduced risk for colorectal cancer, 44% reduced risk for laryngeal cancer, 10% reduced risk for breast cancer, 22% reduced risk for ovarian cancer, 19% reduced risk for prostate cancer, and 31% reduced risk for renal cell cancer, compared to those eating the least garlic.
Onions Protective against Ovarian CancerResearch calculating flavonoid intake in 66,940 women enrolled in the Nurses Health Study between 1984 and 2002 revealed that women whose diets provided the most kaempferol had a 40% reduction in risk of ovarian cancer, compared to women eating the least kaempferol-rich foods. In addition to onions, foods richest in kaempferol include tea (nonherbal), broccoli, curly kale, leeks, spinach, and blueberries.
A significant 34% reduction in ovarian cancer risk was also seen in women with the highest intake of the flavone luteolin (found in citrus). Int J Cancer. 2007 Apr 30; Am J Clin Nutr. 2004 May;79(5):727-47.
Boost Bone HealthMilk isn't the only food that boosts bone health. Onions also help maintain healthy bones, suggests a study published in the Journal of Agricultural and Food Chemistry.A compound newly identified in onions with the long complex name of gamma-L-glutamyl-trans-S-1-propenyl-L-cysteine sulfoxide, GPCS, for short, inhibits the activity of osteoclasts (the cells that break down bone). The more GPCS given in this animal study, the more the bone resorptive (breakdown) action of osteoclasts was inhibited.
Onions may be especially beneficial for women, who are at increased risk for osteoporosis as they go through menopause. Fosamax (Alendronate), the drug typically prescribed to prevent excessive bone loss, works in a similar manner, by destroying osteoclasts, so they do not break down bone. Potential negative side effects of Fosamax include irritation of the upper gastrointestinal mucosa, acid regurgitation, esophageal ulcers and erosions. Potential negative side effects of eating onions: onion breath.
Anti-Inflammatory and Anti-Bacterial ActivitySeveral anti-inflammatory agents in onions render them helpful in reducing the severity of symptoms associated with inflammatory conditions such as the pain and swelling of osteo- and rheumatoid arthritis, the allergic inflammatory response of asthma, and the respiratory congestion associated with the common cold. Both onions and garlic contain compounds that inhibit lipoxygenase and cyclooxygenase (the enzymes that generate inflammatory prostaglandins and thromboxanes), thus markedly reducing inflammation. Onions' anti-inflammatory effects are due not only to their vitamin C and quercitin, but to other active components called isothiocyanates. These compounds work synergistically to spell relief from inflammation. In addition, quercitin and other flavonoids found in onions work with vitamin C to help kill harmful bacteria, making onions an especially good addition to soups and stews during cold and flu season.
DescriptionOnions may bring a tear to your eye, and a pungency to your breath, but they will most certainly bring delight to your tastebuds. The onion, known scientifically as Allium cepa, is, on the surface, a humble brown, white or red, paper-thin skinned bulb; yet, despite its plain looks, has an intense flavor and is a beloved part of the cuisine of almost every region of the world. The word onion comes from the Latin word unio for "single," or "one," because the onion plant produces a single bulb, unlike its cousin, the garlic, that produces many small bulbs. The name also describes the onion bulb when cut down the middle; it is a union (also from unio) of many separate, concentrically arranged layers.
Onions range in size, color and taste depending upon their variety. There are generally two types of large, globe-shaped onions, classified as spring/summer or storage onions. The former class includes those that are grown in warm weather climates and have characteristic mild or sweet tastes. Included in this group are the Maui Sweet Onion (in season April through June), Vidalia (in season May through June) and Walla Walla (in season July and August). Storage onions are grown in colder weather climates and, after harvesting, are dried out for a period of several months, attaining dry, crisp skins. They generally have a more pungent flavor and are usually named by their color: white, yellow or red. Spanish onions fall into this classification. In addition to these large onions, there are also smaller varieties such as the green onion, or scallion, and the pearl onion.
HistoryOnions are native to Asia and the Middle East and have been cultivated for over five thousand years. Onions were highly regarded by the Egyptians. Not only did they use them as currency to pay the workers who built the pyramids, but they also placed them in the tombs of kings, such as Tutankhamen, so that they could carry these gifts bestowed with spiritual significance with them to the afterlife.
Onions have been revered throughout time not only for their culinary use, but also for their therapeutic properties. As early as the 6th century, onions were used as a medicine in India. While they were popular with the ancient Greeks and Romans, they were oftentimes dressed with extra seasonings since many people did not find them spicy enough. Yet, it was their pungency that made onions popular among poor people throughout the world who could freely use this inexpensive vegetable to spark up their meals. Onions were an indispensable vegetable in the cuisines of many European countries during the Middle Ages and later even served as a classic healthy breakfast food. Christopher Columbus brought onions to the West Indies; their cultivation spread from there throughout the Western Hemisphere. Today China, India, the United States, Russian, and Spain are among the leading producers of onions.
How to Select and Store
Onions are a major source of both phenols and flavonoids, phytonutrients that numerous population studies have shown are protective against both cardiovascular disease and cancer. Research published in the November 2004 issue of the Journal of Agricultural and Food Chemistry shows that the variety of onions you choose and the way you prepare them can make a huge difference in the amount of beneficial compounds, and the antioxidant and anti-cancer effects, they deliver.
Shallots and 10 other onion (Allium cepa L.) varieties commonly available in the United States were evaluated: Western Yellow, Northern Red, New York Bold, Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia.
In general, the most pungent onions delivered many times the benefits of their milder cousins.
Shallots had the most phenols, 6 times the amount found in Vidalia onion, the variety with the lowest phenolic content. Shallots also had the most antioxidant activity, followed by Western Yellow, New York Bold, Northern Red, Mexico, Empire Sweet, Western White, Peruvian Sweet, Texas 1015, Imperial Valley Sweet, and Vidalia.
Western Yellow onions had the most flavonoids, 11 times the amount found in Western White, the variety with the lowest flavonoid content.
For all varieties of onions, the more phenols and flavonoids they contained, the more antioxidant and anti-cancer activity they provided.
When tested against liver and colon cancer cells, Western Yellow, New York Bold and shallots were most effective in inhibiting their growth. The milder-tasting varieties, Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia, showed little cancer-fighting ability. So, next time your eyes water when you're slicing onions, be glad. The onion you're cutting is likely to be loaded with beneficial phytonutrients.
Choose onions that are clean, well shaped, have no opening at the neck and feature crisp, dry outer skins. Avoid those that are sprouting or have signs of mold. In addition, onions of inferior quality often have soft spots, moisture at their neck, and dark patches, which may all be indications of decay. As conventionally grown onions are often irradiated to prevent them from sprouting, purchase organically grown varieties since these are not treated with this process.
When purchasing scallions, look for those that have green, fresh-looking tops that appear crisp, yet tender. The base should be whitish in color for two or three inches. Avoid those that have wilted or yellowed tops.
Onions should be stored at room temperature, away from bright light, and in a manner where they are well ventilated. To do this, either place them in a wire hanging basket or a perforated bowl with a raised base so that air can circulate underneath. The length of storage varies with the type of onion. Those that are more pungent in flavor, such as yellow onions, can stay longer than those with a sweeter taste, such as white onions, since the compounds that confer their sharp taste help to preserve them. Scallions should be stored in a plastic bag in the refrigerator where they will keep for about one week. All onions should be stored away from potatoes, as they will absorb their moisture and ethylene gas, causing them to spoil more readily.
The remainder of cut onions should be wrapped tightly in plastic or in a sealed container and should be used within a day or two since they tend to oxidize and lose their nutrient content rather quickly. Cooked onions will best maintain their taste in an airtight container where they can be kept for a few days; they should never be placed in a metal storage container as this may cause them to discolor. Although peeled and chopped onions can be frozen (without first being blanched), this process will cause them to lose some of their flavor.
How to EnjoyFor some of our favorite recipes, click Recipes.
Tips for Preparing Onions:Tips for Preparing Onions:
While many people love to eat onions, most dread cutting them since this process usually brings a tear or two to the eyes. The compound that causes the eyes to burn is a phytonutrient known as allyl sulfate that is produced when sulfur-compounds released by the onion's ruptured cells are exposed to air.
If cutting onions irritates your eyes, there are a few tricks that you can employ. Chill the onions for an hour or so before cutting. This will slow the activity of the enzyme that produces the allyl sulfate and is a better choice than the traditional method of cutting onion under running water. This latter process may dilute the amount of allyl sulfate, which, while it may be irritating to the eyes, is actually one of the phytonutrients most responsible for onions significant health benefits.
Use a very sharp knife and always cut the onions while standing; that way your eyes will be as far away as possible. If cutting onions really makes you cry, consider wearing glasses or goggles.
A Few Quick Serving Ideas:Combine chopped onions, tomatoes, avocado and jalapeno for an all-in-one guacamole salsa dip.
To perk up plain rice, sprinkle some green onions, also known as scallions, and sesame seeds on top.
Sautéed chopped onions are so versatile that they can be added to most any vegetable dish.
Enjoy a classic Italian salad-sliced onions, tomatoes and mozzarella cheese drizzled with olive oil.
Individual ConcernsOnions are not a commonly allergenic food, are not known to contain measurable amounts of oxalates or purines and are also not included in the Environmental Working Group's 2009 report "Shopper's Guide to Pesticides" as one of the 12 foods most frequently containing pesticide residues.
Nutritional ProfileOnions are a very good source of vitamin C, chromium and dietary fiber. They are also a good source of manganese, molybdenum, vitamin B6, folate, potassium, phosphorus and copper.
For an in-depth nutritional profile click here: Onions.
In-Depth Nutritional ProfileIn addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Onions is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more. Introduction to Food Rating System ChartIn order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food's nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.Onions, raw
1.00 cup
160.00 grams
60.80 caloriesNutrientAmountDV
(%)Nutrient
DensityWorld's Healthiest
Foods Ratingchromium24.80 mcg20.76.1very goodvitamin C10.24 mg17.15.1very gooddietary fiber2.88 g11.53.4very goodmanganese0.22 mg11.03.3goodmolybdenum8.00 mcg10.73.2goodvitamin B6 (pyridoxine)0.19 mg9.52.8goodtryptophan0.03 g9.42.8goodfolate30.40 mcg7.62.3goodpotassium251.20 mg7.22.1goodphosphorus52.80 mg5.31.6goodcopper0.10 mg5.01.5goodWorld's Healthiest
Foods RatingRuleexcellentDV>=75%ORDensity>=7.6ANDDV>=10%very goodDV>=50%ORDensity>=3.4ANDDV>=5%goodDV>=25%ORDensity>=1.5ANDDV>=2.5%In-Depth Nutritional Profile for Onions
References
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"Onions" redirects here. For the surname, see Onions (surname).
For other uses, see Onion (disambiguation).
Onion
Onions
Scientific classificationKingdom:Plantae
(unranked):Angiosperms
(unranked):Monocots
Order:Asparagales
Family:Alliaceae
Genus:Allium
Species:A. cepa
Binomial nameAllium cepa
L.Onion is a term used for many plants in the genus Allium. They are known by the common name "onion" but, used without qualifiers, it usually refers to Allium cepa. Allium cepa is also known as the "garden onion" or "bulb" onion. It is grown underground by the plant as a vertical shoot that is used for food storage, leading to the possibility of confusion with a tuber, which it is not.
Allium Cepa is known only in cultivation,[1] but related wild species occur in Central Asia. The most closely-related species include Allium vavilovii Popov & Vved. and Allium asarense R.M. Fritsch & Matin from Iran.[2] However Zohary and Hopf warn that "there are doubts whether the vavilovii collections tested represent genuine wild material or only feral derivatives of the crop."[3]
Contents[hide]
Onions pickled in vinegar are eaten as a snack. These are often served as a side serving in fish and chip shops throughout the United Kingdom and are referred to simply as "Pickled Onions". Onions are widely-used in India and Pakistan and are fundamental in the local cuisine. They are commonly used as a base for curries or made into a paste and eaten as a main course or as a side dish.
Tissue from onions is frequently used in science education to demonstrate microscope usage, because they have particularly large cells which are readily observed even at low magnifications.[4]
Historical usesIt is thought that bulbs from the onion family have been used as a food source for millennia. In Bronze Age settlements, traces of onion remains were found alongside fig and date stones dating back to 5000 BC.[5]
However, it is not clear if these were cultivated onions. Archaeological and literary evidence such as the Book of Numbers 11:5 suggests cultivation probably took place around two thousand years later in ancient Egypt, at the same time that leeks and garlic were cultivated. Workers who built the Egyptian pyramids may have been fed radishes and onions.[5]
The onion is easily propagated, transported and stored. The Ancient Egyptians worshipped it,[6] believing that its spherical shape and concentric rings symbolized eternal life. Onions were even used in Egyptian burials as evidenced by onion traces being found in the eye sockets of Ramesses IV.
In ancient Greece, athletes ate large quantities of onion because it was believed that it would lighten the balance of blood. Roman gladiators were rubbed down with onion to firm up their muscles. In the Middle Ages onions were such an important food that people would pay their rent with onions and even give them as gifts.[6] Doctors were known to prescribe onions to facilitate bowel movements and erection, and also to relieve headaches, coughs, snakebite and hair loss. The onion was introduced to North America byChristopher Columbus on his 1492 expedition to Hispaniola. Onions were also prescribed by doctors in the early 1500s to help with infertility in women, and even dogs and cattle and many other household pets. However, recent evidence has shown that dogs, cats, and other animals should not be given onions in any form, due to toxicity during digestion.[7]
Medicinal properties and health effectsRaw Onions
Nutritional value per 100 g (3.5 oz)Energy 40 kcal 170 kJCarbohydrates 9.34 g- Sugars 4.24 g- Dietary fiber 1.7 g Fat0.1 g- saturated 0.042 g- monounsaturated 0.013 g - polyunsaturated 0.017 g Protein1.1 gWater89.11 gVitamin A equiv. 0 μg 0%Thiamine (Vit. B1) 0.046 mg 4%Riboflavin (Vit. B2) 0.027 mg 2%Niacin (Vit. B3) 0.116 mg 1%Vitamin B6 0.12 mg9%Folate (Vit. B9) 19 μg 5%Vitamin B12 0 μg 0%Vitamin C 7.4 mg12%Vitamin E 0.02 mg0%Vitamin K 0.4 μg0%Calcium 23 mg2%Iron 0.21 mg2%Magnesium 0.129 mg0% Phosphorus 29 mg4%Potassium 146 mg 3%Sodium 4 mg0%Zinc 0.17 mg2%Percentages are relative to US
recommendations for adults.
Source: USDA Nutrient databaseWide-ranging claims have been made for the effectiveness of onions against conditions ranging from the common cold to heart disease, diabetes, osteoporosis, and other diseases.[8] They contain chemical compounds believed to have anti-inflammatory, anticholesterol, anticancer, and antioxidant properties such as quercetin. However, it has not been conclusively demonstrated that increased consumption of onions is directly linked to health benefits. Some studies have shown that increased consumption of onions reduces the risk of head and neck cancers.[9] In India some sects do not eat onion due to its alleged aphrodisiac properties.[10]
In many parts of the world, onions are used to heal blisters and boils. A traditional Maltese remedy for sea urchin wounds is to tie half a baked onion to the afflicted area overnight. An application of raw onion is also said to be helpful in reducing swelling from bee stings. In the United States, products that contain onion extract are used in the treatment of topical scars; some studies have found their action to be ineffective,[11][12][13] while others found that they may act as an anti-inflammatory or bacteriostatic[14] and can improve collagen organization in rabbits.[15]
Onions may be especially beneficial for women,[16] who are at increased risk for osteoporosis as they go through menopause, by destroying osteoclasts so that they do not break down bone.
An American chemist has stated[17] that the pleiomeric chemicals in onions have the potential to alleviate or prevent sore throat. However onion in combination with jaggery has been widely used as a traditional household remedy for sore throat in India.
Shallots have the most phenols, six times the amount found in Vidalia onion, the variety with the lowest phenolic content. Shallots also have the most antioxidant activity, followed by Western Yellow, pungent yellow (New York Bold[18]), Northern Red, Mexico, Empire Sweet, Western White, Peruvian Sweet, Texas 1015, Imperial Valley Sweet, and Vidalia. Western Yellow onions have the most flavonoids, eleven times the amount found in Western White, the variety with the lowest flavonoid content.
For all varieties of onions, the more phenols and flavonoids they contain, the more antioxidant and anti-cancer activity they provide. When tested against liver and colon cancer cells, Western Yellow, pungent yellow (New York Bold[18]) and shallots were most effective in inhibiting their growth. The milder-tasting varieties—Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia—showed little cancer-fighting ability.[18]
Shallots and ten other onion (Allium cepa L.) varieties commonly available in the United States were evaluated: Western Yellow, Northern Red, pungent yellow (New York Bold), Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia. In general, the most pungent onions delivered many times the benefits of their milder cousins.[18]
Allergies and eye irritationSome people suffer from from allergies to plants in the allium family. If you are allergic to onions, then you can be allergic to all plants under the family liliaceae (lilies). This can include reactions to onions, garlic, chives, leeks, shallots, garden lilies, ginger, and bananas. Symptoms can include irritable bowel, diarrhea, mouth and throat ulcerations, nausea, breathing difficulties, and in rare cases anaphylaxis. Garlic-sensitive patients show positive tests to diallyldisulfide, allylpropyldisulfide, allylmercaptan and allicin, all present in garlic. Even if garlic is present in a very small amount, it can lead to an allergic reaction.
As onions are sliced or eaten, cells are broken, allowing enzymes called alliinases to break down amino acid sulphoxides and generate sulphenic acids. Sulphenic acids are unstable and spontaneously rearrange into a volatile gas called syn-propanethial-S-oxide. The gas diffuses through the air and eventually reaches the eye, where it binds to sensory neurons, creating a stinging sensation. Tear glands produce tears to dilute and flush out the irritant.[19]
Supplying ample water to the reaction while peeling onions prevents the gas from reaching the eyes. Eye irritation can, therefore, be avoided by cutting onions under running water or submerged in a basin of water.[19] Rinsing the onion and leaving it wet while chopping may also be effective. Another way to reduce irritation is by chilling, or by not cutting off the root of the onion (or by doing it last), as the root of the onion has a higher concentration of enzymes.[20] Using a sharp blade to chop onions will limit the cell damage and the release of enzymes that drive the irritation response. Chilling or freezing onions prevents the enzymes from activating, limiting the amount of gas generated. Eye irritation may be avoided by having a fan blow the gas away from the eyes as the onion is being cut.
It is also possible to avoid eye irritation by wearing goggles or any eye protection that creates a seal around the eye. Contact lens wearers can experience less immediate irritation as a result of the slight protection afforded by the lenses themselves. It may also be that lens wearers are familiar with controlling the more reflexive actions of their eyes with regards to irritation; as this is an ability they require when manipulating the lenses to prevent blinking.
The volume of sulfenic acids released, and the irritation effect, differs among Allium species. On January 31 , 2008, the New Zealand Crop and Food institute created a strain of "no tears" onions by using gene-silencing biotechnology.[21]
[edit] Propagation
Onion and shallot output in 2005
Onion growing shoots
Onions may be grown from seed or, more commonly today, from sets started from seed the previous year. Onion sets are produced by sowing seed very thickly one year, resulting in stunted plants which produce very small bulbs. These bulbs are very easy to set out and grow into mature bulbs the following year, but they have the reputation of producing a less durable bulb than onions grown directly from seed and thinned.
Seed-bearing onions are day-length sensitive; their bulbs begin growing only after the number of daylight hours has surpassed some minimal quantity. Most traditional European onions are what is referred to as "long-day" onions, producing bulbs only after 15+ hours of daylight occur. Southern European and North African varieties are often known as "intermediate day" types, requiring only 12–13 hours of daylight to stimulate bulb formation. Finally, "short-day" onions, which have been developed in more recent times, are planted in mild-winter areas in the fall and form bulbs in the early spring, and require only 9–10 hours of sunlight to stimulate bulb formation.
Either planting method may be used to produce spring onions or green onions, which are the leaves and/or immature plants. Green onion is a name also used to refer to another species, Allium fistulosum, the Welsh onion, which is said not to produce dry bulbs.
The tree onion produces bulbs instead of flowers and seeds, which can be planted directly in the ground.
Varieties
Brown and white onions
Yellow onions
Flower head of a yellow onion
Red onions
Onion field during harvest, Vale, Oregon (USA).
Top Ten Onions Producers — 2005
(1000 tonnes) India9,793 China5,500 United States3,346 Turkey2,220 Pakistan1,764 Russia1,758 South Korea1,750 Japan1,637 Egypt1,302 Spain1,149World Total64,101Source:
UN Food & Agriculture Organisation (FAO)[22]The Onion Futures Act, passed in 1958, bans the trading of futures contracts on onions in the United States, after farmers complained about alleged market manipulation at the Chicago Mercantile Exchange. It provideseconomists with a unique case study in the effects of futures trading on agricultural prices. It remains in effect as of 2009.
[edit] Aroma attributes[edit] Potential medicinal use3-mercapto-2-methylpentan-1-ol in onion was found to have an antioxidant potent which inhibites peroxynitrite induced diseases.[25]
[edit] Language
Lists of miscellaneous information should be avoided. Please relocate any relevant information into appropriate sections or articles. (April 2009)
Red onion
Onion fields near Elba, New York
Onions cooked in a frying pan
Onion weighing and packing in The Netherlands
Cut onion
Spring onion
See alsoNotes
What would a kitchen be without the distinctively pungent smell and taste of onions filling out the flavors of almost every type of cuisine imaginable? Fortunately, yellow storage onions are available throughout the year but sweet varieties have a much more limited growing season and are available only a few months out of the year.
The word onion comes from the Latin word unio for "single," or "one," because the onion plant produces a single bulb, unlike its cousin, the garlic, that produces many small bulbs. The name also describes the union (also from unio) of the many separate, concentrically arranged layers of the onion.
This chart graphically details the %DV that a serving of Onions provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Onions can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Onions, featuring information over 80 nutrients, can be found under the Food Rating System Chart.
- Health Benefits
- Description
- History
- How to Select and Store
- How to Enjoy
- Individual Concerns
- Nutritional Profile
- References
Blood Sugar-Lowering EffectsThe higher the intake of onion, the lower the level of glucose found during oral or intravenous glucose tolerance tests. Experimental and clinical evidence suggests that allyl propyl disulfide is responsible for this effect and lowers blood sugar levels by increasing the amount of free insulin available. Allyl propyl disulfide does this by competing with insulin, which is also a disulphide, to occupy the sites in the liver where insulin is inactivated. This results is an increase in the amount of insulin available to usher glucose into cells causing a lowering of blood sugar.
In addition, onions are a very good source of chromium, the mineral component in glucose tolerance factor, a molecule that helps cells respond appropriately to insulin. Clinical studies of diabetics have shown that chromium can decrease fasting blood glucose levels, improve glucose tolerance, lower insulin levels, and decrease total cholesterol and triglyceride levels, while increasing good HDL-cholesterol levels. Marginal chromium deficiency is common in the United States, not surprising since chromium levels are depleted by the consumption refined sugars and white flour products as well as the lack of exercise. One cup of raw onion contains over 20% of the Daily Value for this important trace mineral.
Cardiovascular BenefitsThe regular consumption of onions has, like garlic, been shown to lower high cholesterol levels and high blood pressure, both of which help prevent atherosclerosis and diabetic heart disease, and reduce the risk of heart attack or stroke. These beneficial effects are likely due to onions' sulfur compounds, its chromium and its vitamin B6, which helps prevent heart disease by lowering high homocysteine levels, another significant risk factor for heart attack and stroke.
Onions have been singled out as one of the small number of vegetables and fruits that contributed to the significant reduction in heart disease risk seen in a meta-analysis of seven prospective studies. Of the more than 100,000 individuals who participated in these studies, those who diets most frequently included onions, tea, apples and broccoli-the richest sources of flavonoids-gained a 20% reduction in their risk of heart disease.
Support Gastrointestinal HealthThe regular consumption of onions, as little as two or more times per week, is associated with a significantly reduced risk of developing colon cancer. Onions contain a number of flavonoids, the most studied of which, quercitin, has been shown to halt the growth of tumors in animals and to protect colon cells from the damaging effects of certain cancer-causing substances. Cooking meats with onions may help reduce the amount of carcinogens produced when meat is cooked using high heat methods.
Quercitin, an antioxidant in onions, and curcumin, a phytonutrient found in the curry spice turmeric, reduce both the size and number of precancerous lesions in the human intestinal tract, suggests research published in Clinical Gasteroenterology and Hepatology.
Five patients with an inherited form of precancerous polyps in the lower bowel known as familial adenomatous polyposis (FAP) were treated with regular doses of curcumin and quercetin over an average of six months. The average number of polyps dropped 60.4%, and the average size of the polyps that did develop dropped by 50.9%.
FAP runs in families and is characterized by the development of hundreds of polyps (colorectal adenomas) and, eventually, colon cancer. Recently, nonsteroidal anti-inflammatory drugs (NSAIDs such as aspirin, ibuprofen) have been used to treat some patients with this condition, but these drugs often produce significant side effects, including gastrointestinal ulcerations and bleeding, according to lead researcher Francis M. Giardiello, M.D., at the Division of Gastroenterology, Johns Hopkins University.
Previous observational studies in populations that consume large amounts of curry, as well as animal research, have strongly suggested that curcumin, one of the main ingredients in Asian curries, might be effective in preventing and/or treating cancer in the lower intestine. Similarly, quercetin, an anti-oxidant flavonoid found in a variety of foods including onions, green tea and red wine, has been shown to inhibit growth of colon cancer cell lines in humans and abnormal colorectal cells in animals.
In this study, a decrease in polyp number was observed in four of five patients at three months and four of four patients at six months.
Each patient received curcumin (480 mg) and quercetin (20 mg) orally 3 times a day for 6 months. Although the amount of quercetin was similar to what many people consume daily, the curcumin consumed was more than would be provided in a typical diet because turmeric only contains on average 3-5 % curcumin by weight. While simply consuming curry and onions may not have as dramatic an effect as was produced in this study, this research clearly demonstrates that liberal use of onions and turmeric and onions can play a protective role against the development of colorectal cancer.
Onion and Garlic Protective against Many CancersMaking onion and garlic a staple in your healthy way of eating may greatly lower your risk of several common cancers, suggests a large data set of case-control studies from Southern European populations (Galeone C, Pelucchi C et al, American Journal of Clinical Nutrition).
Study participants consuming the most onions showed an 84% reduced risk for cancer of the oral cavity and pharynx, 88% reduced risk for esophageal cancer, 56% reduced risk for colorectal cancer, 83% reduced risk for laryngeal cancer, 25% reduced risk for breast cancer, 73% reduced risk for ovarian cancer, 71% reduced risk for prostate cancer, and 38% reduced risk for renal cell cancer, compared to those eating the least onions. Similarly, those eating the most garlic had a 39% reduced risk for cancer of the oral cavity and pharynx, 57% reduced risk for esophageal cancer, 26% reduced risk for colorectal cancer, 44% reduced risk for laryngeal cancer, 10% reduced risk for breast cancer, 22% reduced risk for ovarian cancer, 19% reduced risk for prostate cancer, and 31% reduced risk for renal cell cancer, compared to those eating the least garlic.
Onions Protective against Ovarian CancerResearch calculating flavonoid intake in 66,940 women enrolled in the Nurses Health Study between 1984 and 2002 revealed that women whose diets provided the most kaempferol had a 40% reduction in risk of ovarian cancer, compared to women eating the least kaempferol-rich foods. In addition to onions, foods richest in kaempferol include tea (nonherbal), broccoli, curly kale, leeks, spinach, and blueberries.
A significant 34% reduction in ovarian cancer risk was also seen in women with the highest intake of the flavone luteolin (found in citrus). Int J Cancer. 2007 Apr 30; Am J Clin Nutr. 2004 May;79(5):727-47.
Boost Bone HealthMilk isn't the only food that boosts bone health. Onions also help maintain healthy bones, suggests a study published in the Journal of Agricultural and Food Chemistry.A compound newly identified in onions with the long complex name of gamma-L-glutamyl-trans-S-1-propenyl-L-cysteine sulfoxide, GPCS, for short, inhibits the activity of osteoclasts (the cells that break down bone). The more GPCS given in this animal study, the more the bone resorptive (breakdown) action of osteoclasts was inhibited.
Onions may be especially beneficial for women, who are at increased risk for osteoporosis as they go through menopause. Fosamax (Alendronate), the drug typically prescribed to prevent excessive bone loss, works in a similar manner, by destroying osteoclasts, so they do not break down bone. Potential negative side effects of Fosamax include irritation of the upper gastrointestinal mucosa, acid regurgitation, esophageal ulcers and erosions. Potential negative side effects of eating onions: onion breath.
Anti-Inflammatory and Anti-Bacterial ActivitySeveral anti-inflammatory agents in onions render them helpful in reducing the severity of symptoms associated with inflammatory conditions such as the pain and swelling of osteo- and rheumatoid arthritis, the allergic inflammatory response of asthma, and the respiratory congestion associated with the common cold. Both onions and garlic contain compounds that inhibit lipoxygenase and cyclooxygenase (the enzymes that generate inflammatory prostaglandins and thromboxanes), thus markedly reducing inflammation. Onions' anti-inflammatory effects are due not only to their vitamin C and quercitin, but to other active components called isothiocyanates. These compounds work synergistically to spell relief from inflammation. In addition, quercitin and other flavonoids found in onions work with vitamin C to help kill harmful bacteria, making onions an especially good addition to soups and stews during cold and flu season.
DescriptionOnions may bring a tear to your eye, and a pungency to your breath, but they will most certainly bring delight to your tastebuds. The onion, known scientifically as Allium cepa, is, on the surface, a humble brown, white or red, paper-thin skinned bulb; yet, despite its plain looks, has an intense flavor and is a beloved part of the cuisine of almost every region of the world. The word onion comes from the Latin word unio for "single," or "one," because the onion plant produces a single bulb, unlike its cousin, the garlic, that produces many small bulbs. The name also describes the onion bulb when cut down the middle; it is a union (also from unio) of many separate, concentrically arranged layers.
Onions range in size, color and taste depending upon their variety. There are generally two types of large, globe-shaped onions, classified as spring/summer or storage onions. The former class includes those that are grown in warm weather climates and have characteristic mild or sweet tastes. Included in this group are the Maui Sweet Onion (in season April through June), Vidalia (in season May through June) and Walla Walla (in season July and August). Storage onions are grown in colder weather climates and, after harvesting, are dried out for a period of several months, attaining dry, crisp skins. They generally have a more pungent flavor and are usually named by their color: white, yellow or red. Spanish onions fall into this classification. In addition to these large onions, there are also smaller varieties such as the green onion, or scallion, and the pearl onion.
HistoryOnions are native to Asia and the Middle East and have been cultivated for over five thousand years. Onions were highly regarded by the Egyptians. Not only did they use them as currency to pay the workers who built the pyramids, but they also placed them in the tombs of kings, such as Tutankhamen, so that they could carry these gifts bestowed with spiritual significance with them to the afterlife.
Onions have been revered throughout time not only for their culinary use, but also for their therapeutic properties. As early as the 6th century, onions were used as a medicine in India. While they were popular with the ancient Greeks and Romans, they were oftentimes dressed with extra seasonings since many people did not find them spicy enough. Yet, it was their pungency that made onions popular among poor people throughout the world who could freely use this inexpensive vegetable to spark up their meals. Onions were an indispensable vegetable in the cuisines of many European countries during the Middle Ages and later even served as a classic healthy breakfast food. Christopher Columbus brought onions to the West Indies; their cultivation spread from there throughout the Western Hemisphere. Today China, India, the United States, Russian, and Spain are among the leading producers of onions.
How to Select and Store
Onions are a major source of both phenols and flavonoids, phytonutrients that numerous population studies have shown are protective against both cardiovascular disease and cancer. Research published in the November 2004 issue of the Journal of Agricultural and Food Chemistry shows that the variety of onions you choose and the way you prepare them can make a huge difference in the amount of beneficial compounds, and the antioxidant and anti-cancer effects, they deliver.
Shallots and 10 other onion (Allium cepa L.) varieties commonly available in the United States were evaluated: Western Yellow, Northern Red, New York Bold, Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia.
In general, the most pungent onions delivered many times the benefits of their milder cousins.
Shallots had the most phenols, 6 times the amount found in Vidalia onion, the variety with the lowest phenolic content. Shallots also had the most antioxidant activity, followed by Western Yellow, New York Bold, Northern Red, Mexico, Empire Sweet, Western White, Peruvian Sweet, Texas 1015, Imperial Valley Sweet, and Vidalia.
Western Yellow onions had the most flavonoids, 11 times the amount found in Western White, the variety with the lowest flavonoid content.
For all varieties of onions, the more phenols and flavonoids they contained, the more antioxidant and anti-cancer activity they provided.
When tested against liver and colon cancer cells, Western Yellow, New York Bold and shallots were most effective in inhibiting their growth. The milder-tasting varieties, Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia, showed little cancer-fighting ability. So, next time your eyes water when you're slicing onions, be glad. The onion you're cutting is likely to be loaded with beneficial phytonutrients.
Choose onions that are clean, well shaped, have no opening at the neck and feature crisp, dry outer skins. Avoid those that are sprouting or have signs of mold. In addition, onions of inferior quality often have soft spots, moisture at their neck, and dark patches, which may all be indications of decay. As conventionally grown onions are often irradiated to prevent them from sprouting, purchase organically grown varieties since these are not treated with this process.
When purchasing scallions, look for those that have green, fresh-looking tops that appear crisp, yet tender. The base should be whitish in color for two or three inches. Avoid those that have wilted or yellowed tops.
Onions should be stored at room temperature, away from bright light, and in a manner where they are well ventilated. To do this, either place them in a wire hanging basket or a perforated bowl with a raised base so that air can circulate underneath. The length of storage varies with the type of onion. Those that are more pungent in flavor, such as yellow onions, can stay longer than those with a sweeter taste, such as white onions, since the compounds that confer their sharp taste help to preserve them. Scallions should be stored in a plastic bag in the refrigerator where they will keep for about one week. All onions should be stored away from potatoes, as they will absorb their moisture and ethylene gas, causing them to spoil more readily.
The remainder of cut onions should be wrapped tightly in plastic or in a sealed container and should be used within a day or two since they tend to oxidize and lose their nutrient content rather quickly. Cooked onions will best maintain their taste in an airtight container where they can be kept for a few days; they should never be placed in a metal storage container as this may cause them to discolor. Although peeled and chopped onions can be frozen (without first being blanched), this process will cause them to lose some of their flavor.
How to EnjoyFor some of our favorite recipes, click Recipes.
Tips for Preparing Onions:Tips for Preparing Onions:
While many people love to eat onions, most dread cutting them since this process usually brings a tear or two to the eyes. The compound that causes the eyes to burn is a phytonutrient known as allyl sulfate that is produced when sulfur-compounds released by the onion's ruptured cells are exposed to air.
If cutting onions irritates your eyes, there are a few tricks that you can employ. Chill the onions for an hour or so before cutting. This will slow the activity of the enzyme that produces the allyl sulfate and is a better choice than the traditional method of cutting onion under running water. This latter process may dilute the amount of allyl sulfate, which, while it may be irritating to the eyes, is actually one of the phytonutrients most responsible for onions significant health benefits.
Use a very sharp knife and always cut the onions while standing; that way your eyes will be as far away as possible. If cutting onions really makes you cry, consider wearing glasses or goggles.
A Few Quick Serving Ideas:Combine chopped onions, tomatoes, avocado and jalapeno for an all-in-one guacamole salsa dip.
To perk up plain rice, sprinkle some green onions, also known as scallions, and sesame seeds on top.
Sautéed chopped onions are so versatile that they can be added to most any vegetable dish.
Enjoy a classic Italian salad-sliced onions, tomatoes and mozzarella cheese drizzled with olive oil.
Individual ConcernsOnions are not a commonly allergenic food, are not known to contain measurable amounts of oxalates or purines and are also not included in the Environmental Working Group's 2009 report "Shopper's Guide to Pesticides" as one of the 12 foods most frequently containing pesticide residues.
Nutritional ProfileOnions are a very good source of vitamin C, chromium and dietary fiber. They are also a good source of manganese, molybdenum, vitamin B6, folate, potassium, phosphorus and copper.
For an in-depth nutritional profile click here: Onions.
In-Depth Nutritional ProfileIn addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Onions is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more. Introduction to Food Rating System ChartIn order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food's nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.Onions, raw
1.00 cup
160.00 grams
60.80 caloriesNutrientAmountDV
(%)Nutrient
DensityWorld's Healthiest
Foods Ratingchromium24.80 mcg20.76.1very goodvitamin C10.24 mg17.15.1very gooddietary fiber2.88 g11.53.4very goodmanganese0.22 mg11.03.3goodmolybdenum8.00 mcg10.73.2goodvitamin B6 (pyridoxine)0.19 mg9.52.8goodtryptophan0.03 g9.42.8goodfolate30.40 mcg7.62.3goodpotassium251.20 mg7.22.1goodphosphorus52.80 mg5.31.6goodcopper0.10 mg5.01.5goodWorld's Healthiest
Foods RatingRuleexcellentDV>=75%ORDensity>=7.6ANDDV>=10%very goodDV>=50%ORDensity>=3.4ANDDV>=5%goodDV>=25%ORDensity>=1.5ANDDV>=2.5%In-Depth Nutritional Profile for Onions
References
- Ali M, Thomson M, Afzal M. Garlic and onions: their effect on eicosanoid metabolism and its clinical relevance. Prostaglandins Leukot Essent Fatty Acids. 2000 Feb;62(2):55-73. Review 2000.
- Augusti KT. Therapeutic values of onion (Allium cepa L.) and garlic (Allium sativum L.). Indian J Exp Biol. 1996 Jul;34(7):634-40. Review 1996.
- Challier B, Perarnau JM, Viel JF. Garlic, onion and cereal fibre as protective factors for breast cancer: a French case-control study. Eur J Epidemiol 1998 Dec;14(8):737-47 1998. PMID:13640.
- Cruz-Correa M, Shoskes DA, Sanchez P, Zhao R, Hylind LM, Wexner SD, Giardiello FM. Combination treatment with curcumin and quercetin of adenomas in familial adenomatous polyposis. i>Clin Gastroenterol Hepatol. 2006 Aug;4(8):1035-8. Epub 2006 Jun 6. 2006. PMID:16757216.
- Dorant E, van den Brandt PA, Goldbohm RA. A prospective cohort study on the relationship between onion and leek consumption, garlic supplement use and the risk of colorectal carcinoma in The Netherlands. Carcinogenesis 1996 Mar;17(3):477-84 1996. PMID:13660.
- Dorsch W, Ettl M, Hein G, et al. Antiasthmatic effects of onions. Inhibition of platelet-activating factor-induced bronchial obstruction by onion oils. Int Arch Allergy Appl Immunol. 1987;82(3-4):535-6 1987.
- Ensminger AH, Ensminger, ME, Kondale JE, Robson JRK. Foods & Nutriton Encyclopedia. Pegus Press, Clovis, California 1983.
- Ensminger AH, Esminger M. K. J. e. al. Food for Health: A Nutrition Encyclopedia. Clovis, California: Pegus Press; 1986 1986. PMID:15210.
- Fortin, Francois, Editorial Director. The Visual Foods Encyclopedia. Macmillan, New York 1996.
- Fukushima S, Takada N, Hori T, Wanibuchi H. Cancer prevention by organosulfur compounds from garlic and onion. J Cell Biochem Suppl 1997;27:100-5 1997. PMID:13650.
- Galeone C, Pelucchi C, Levi F, Negri E, Franceschi S, Talamini R, Giacosa A, La Vecchia C. Onion and garlic use and human cancer. Am J Clin Nutr. 2006 Nov;84(5):1027-32. 2006. PMID:17093154.
- Gates MA, Tworoger SS, Hecht JL, De Vivo I, Rosner B, Hankinson SE. A prospective study of dietary flavonoid intake and incidence of epithelial ovarian cancer. Int J Cancer. 2007 Apr 30; [Epub ahead of print] 2007. PMID:17471564.
- Gee JM, Hara HT. Suppression of Intestinal Crypt Cell Proliferation and Aberrant Crypt Foci by Dietary Quercetin in Rats. Nutr Cancer 2002;43(2):121-126 2002.
- Grieve M. A Modern Herbal. Dover Publications, New York 1971.
- Huxley RR, Neil HAW. The relation between dietary flavonol intake and coronary heart disease mortality: a meta-analysis of prospective cohort studies,. European Journal of Clinical Nutrition (2003) 57, 904-908. 2003.
- Manach C, Scalbert A, Morand C, Rémésy C, Jiménez L. Polyphenols: food sources and bioavailability. Am J Clin Nutr. 2004 May;79(5):727-47. 2004. PMID:15113710.
- Moon JH, Nakata R, Oshima S, et al. Accumulation of quercetin conjugates in blood plasma after the short-term ingestion of onion by women. Am J Physiol Regul Integr Comp Physiol. 2000 Aug;279(2):R461-7 2000.
- Riley DM, Bianchini F, Vainio H. Allium vegetables and organosulfur compounds: do they help prevent cancer. Environ Health Perspect 2001 Sep;109(9):893-902 2001. PMID:13600.
- Sheela CG, Kumud K, Augusti KT. Anti-diabetic effects of onion and garlic sulfoxide amino acids in rats. Planta Med. 1995 Aug;61(4):356-7 1995.
- Vanderhoek J, Makheja A, Bailey J. Inhibition of fatty acid lipoxygenases by onion and garlic oils: Evidence for the mechanism by which these oils inhibit platelet aggregation. Bioch Pharmacol 29 (1980):3169-73 1980.
- Wagner H, Dorsch W, Bayer T, et al. Antiasthmatic effects of onions: inhibition of 5-lipoxygenase and cyclooxygenase in vitro by thiosulfinates and "Cepaenes". Prostaglandins Leukot Essent Fatty Acids. 1990 Jan;39(1):59-62 1990.
- Wetli HA, Brenneisen R, Tschudi I, Langos M, Bigler P, Sprang T, Schurch S, Muhlbauer RC. A gamma-Glutamyl Peptide Isolated from Onion (Allium cepa L.) by Bioassay-Guided Fractionation Inhibits Resorption Activity of Osteoclasts. J Agric Food Chem. 2005 May 4;53(9):3408-3414. 2005. PMID:15853380.
- Wood, Rebecca. The Whole Foods Encyclopedia. New York, NY: Prentice-Hall Press; 1988 1988. PMID:15220.
- Yang J, Meyers KJ, van der Heide J, Liu RH. Varietal Differences in Phenolic Content and Antioxidant and Antiproliferative Activities of Onions. J Agric Food Chem. 2004 Nov 3;52(22):6787-6793. 2004. PMID:15506817.
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"Onions" redirects here. For the surname, see Onions (surname).
For other uses, see Onion (disambiguation).
Onion
Onions
Scientific classificationKingdom:Plantae
(unranked):Angiosperms
(unranked):Monocots
Order:Asparagales
Family:Alliaceae
Genus:Allium
Species:A. cepa
Binomial nameAllium cepa
L.Onion is a term used for many plants in the genus Allium. They are known by the common name "onion" but, used without qualifiers, it usually refers to Allium cepa. Allium cepa is also known as the "garden onion" or "bulb" onion. It is grown underground by the plant as a vertical shoot that is used for food storage, leading to the possibility of confusion with a tuber, which it is not.
Allium Cepa is known only in cultivation,[1] but related wild species occur in Central Asia. The most closely-related species include Allium vavilovii Popov & Vved. and Allium asarense R.M. Fritsch & Matin from Iran.[2] However Zohary and Hopf warn that "there are doubts whether the vavilovii collections tested represent genuine wild material or only feral derivatives of the crop."[3]
Contents[hide]
- 1 Uses
- 2 Historical uses
- 3 Medicinal properties and health effects
- 4 Allergies and eye irritation
- 5 Propagation
- 6 Varieties
- 7 Production trends
- 8 Aroma attributes
- 9 Potential medicinal use
- 10 Language
- 11 Pictures
- 12 See also
- 13 Notes
- 14 References
- 15 External links
Onions pickled in vinegar are eaten as a snack. These are often served as a side serving in fish and chip shops throughout the United Kingdom and are referred to simply as "Pickled Onions". Onions are widely-used in India and Pakistan and are fundamental in the local cuisine. They are commonly used as a base for curries or made into a paste and eaten as a main course or as a side dish.
Tissue from onions is frequently used in science education to demonstrate microscope usage, because they have particularly large cells which are readily observed even at low magnifications.[4]
Historical usesIt is thought that bulbs from the onion family have been used as a food source for millennia. In Bronze Age settlements, traces of onion remains were found alongside fig and date stones dating back to 5000 BC.[5]
However, it is not clear if these were cultivated onions. Archaeological and literary evidence such as the Book of Numbers 11:5 suggests cultivation probably took place around two thousand years later in ancient Egypt, at the same time that leeks and garlic were cultivated. Workers who built the Egyptian pyramids may have been fed radishes and onions.[5]
The onion is easily propagated, transported and stored. The Ancient Egyptians worshipped it,[6] believing that its spherical shape and concentric rings symbolized eternal life. Onions were even used in Egyptian burials as evidenced by onion traces being found in the eye sockets of Ramesses IV.
In ancient Greece, athletes ate large quantities of onion because it was believed that it would lighten the balance of blood. Roman gladiators were rubbed down with onion to firm up their muscles. In the Middle Ages onions were such an important food that people would pay their rent with onions and even give them as gifts.[6] Doctors were known to prescribe onions to facilitate bowel movements and erection, and also to relieve headaches, coughs, snakebite and hair loss. The onion was introduced to North America byChristopher Columbus on his 1492 expedition to Hispaniola. Onions were also prescribed by doctors in the early 1500s to help with infertility in women, and even dogs and cattle and many other household pets. However, recent evidence has shown that dogs, cats, and other animals should not be given onions in any form, due to toxicity during digestion.[7]
Medicinal properties and health effectsRaw Onions
Nutritional value per 100 g (3.5 oz)Energy 40 kcal 170 kJCarbohydrates 9.34 g- Sugars 4.24 g- Dietary fiber 1.7 g Fat0.1 g- saturated 0.042 g- monounsaturated 0.013 g - polyunsaturated 0.017 g Protein1.1 gWater89.11 gVitamin A equiv. 0 μg 0%Thiamine (Vit. B1) 0.046 mg 4%Riboflavin (Vit. B2) 0.027 mg 2%Niacin (Vit. B3) 0.116 mg 1%Vitamin B6 0.12 mg9%Folate (Vit. B9) 19 μg 5%Vitamin B12 0 μg 0%Vitamin C 7.4 mg12%Vitamin E 0.02 mg0%Vitamin K 0.4 μg0%Calcium 23 mg2%Iron 0.21 mg2%Magnesium 0.129 mg0% Phosphorus 29 mg4%Potassium 146 mg 3%Sodium 4 mg0%Zinc 0.17 mg2%Percentages are relative to US
recommendations for adults.
Source: USDA Nutrient databaseWide-ranging claims have been made for the effectiveness of onions against conditions ranging from the common cold to heart disease, diabetes, osteoporosis, and other diseases.[8] They contain chemical compounds believed to have anti-inflammatory, anticholesterol, anticancer, and antioxidant properties such as quercetin. However, it has not been conclusively demonstrated that increased consumption of onions is directly linked to health benefits. Some studies have shown that increased consumption of onions reduces the risk of head and neck cancers.[9] In India some sects do not eat onion due to its alleged aphrodisiac properties.[10]
In many parts of the world, onions are used to heal blisters and boils. A traditional Maltese remedy for sea urchin wounds is to tie half a baked onion to the afflicted area overnight. An application of raw onion is also said to be helpful in reducing swelling from bee stings. In the United States, products that contain onion extract are used in the treatment of topical scars; some studies have found their action to be ineffective,[11][12][13] while others found that they may act as an anti-inflammatory or bacteriostatic[14] and can improve collagen organization in rabbits.[15]
Onions may be especially beneficial for women,[16] who are at increased risk for osteoporosis as they go through menopause, by destroying osteoclasts so that they do not break down bone.
An American chemist has stated[17] that the pleiomeric chemicals in onions have the potential to alleviate or prevent sore throat. However onion in combination with jaggery has been widely used as a traditional household remedy for sore throat in India.
Shallots have the most phenols, six times the amount found in Vidalia onion, the variety with the lowest phenolic content. Shallots also have the most antioxidant activity, followed by Western Yellow, pungent yellow (New York Bold[18]), Northern Red, Mexico, Empire Sweet, Western White, Peruvian Sweet, Texas 1015, Imperial Valley Sweet, and Vidalia. Western Yellow onions have the most flavonoids, eleven times the amount found in Western White, the variety with the lowest flavonoid content.
For all varieties of onions, the more phenols and flavonoids they contain, the more antioxidant and anti-cancer activity they provide. When tested against liver and colon cancer cells, Western Yellow, pungent yellow (New York Bold[18]) and shallots were most effective in inhibiting their growth. The milder-tasting varieties—Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia—showed little cancer-fighting ability.[18]
Shallots and ten other onion (Allium cepa L.) varieties commonly available in the United States were evaluated: Western Yellow, Northern Red, pungent yellow (New York Bold), Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia. In general, the most pungent onions delivered many times the benefits of their milder cousins.[18]
Allergies and eye irritationSome people suffer from from allergies to plants in the allium family. If you are allergic to onions, then you can be allergic to all plants under the family liliaceae (lilies). This can include reactions to onions, garlic, chives, leeks, shallots, garden lilies, ginger, and bananas. Symptoms can include irritable bowel, diarrhea, mouth and throat ulcerations, nausea, breathing difficulties, and in rare cases anaphylaxis. Garlic-sensitive patients show positive tests to diallyldisulfide, allylpropyldisulfide, allylmercaptan and allicin, all present in garlic. Even if garlic is present in a very small amount, it can lead to an allergic reaction.
As onions are sliced or eaten, cells are broken, allowing enzymes called alliinases to break down amino acid sulphoxides and generate sulphenic acids. Sulphenic acids are unstable and spontaneously rearrange into a volatile gas called syn-propanethial-S-oxide. The gas diffuses through the air and eventually reaches the eye, where it binds to sensory neurons, creating a stinging sensation. Tear glands produce tears to dilute and flush out the irritant.[19]
Supplying ample water to the reaction while peeling onions prevents the gas from reaching the eyes. Eye irritation can, therefore, be avoided by cutting onions under running water or submerged in a basin of water.[19] Rinsing the onion and leaving it wet while chopping may also be effective. Another way to reduce irritation is by chilling, or by not cutting off the root of the onion (or by doing it last), as the root of the onion has a higher concentration of enzymes.[20] Using a sharp blade to chop onions will limit the cell damage and the release of enzymes that drive the irritation response. Chilling or freezing onions prevents the enzymes from activating, limiting the amount of gas generated. Eye irritation may be avoided by having a fan blow the gas away from the eyes as the onion is being cut.
It is also possible to avoid eye irritation by wearing goggles or any eye protection that creates a seal around the eye. Contact lens wearers can experience less immediate irritation as a result of the slight protection afforded by the lenses themselves. It may also be that lens wearers are familiar with controlling the more reflexive actions of their eyes with regards to irritation; as this is an ability they require when manipulating the lenses to prevent blinking.
The volume of sulfenic acids released, and the irritation effect, differs among Allium species. On January 31 , 2008, the New Zealand Crop and Food institute created a strain of "no tears" onions by using gene-silencing biotechnology.[21]
[edit] Propagation
Onion and shallot output in 2005
Onion growing shoots
Onions may be grown from seed or, more commonly today, from sets started from seed the previous year. Onion sets are produced by sowing seed very thickly one year, resulting in stunted plants which produce very small bulbs. These bulbs are very easy to set out and grow into mature bulbs the following year, but they have the reputation of producing a less durable bulb than onions grown directly from seed and thinned.
Seed-bearing onions are day-length sensitive; their bulbs begin growing only after the number of daylight hours has surpassed some minimal quantity. Most traditional European onions are what is referred to as "long-day" onions, producing bulbs only after 15+ hours of daylight occur. Southern European and North African varieties are often known as "intermediate day" types, requiring only 12–13 hours of daylight to stimulate bulb formation. Finally, "short-day" onions, which have been developed in more recent times, are planted in mild-winter areas in the fall and form bulbs in the early spring, and require only 9–10 hours of sunlight to stimulate bulb formation.
Either planting method may be used to produce spring onions or green onions, which are the leaves and/or immature plants. Green onion is a name also used to refer to another species, Allium fistulosum, the Welsh onion, which is said not to produce dry bulbs.
The tree onion produces bulbs instead of flowers and seeds, which can be planted directly in the ground.
Varieties
Brown and white onions
Yellow onions
Flower head of a yellow onion
Red onions
- Bulb onion – Grown from seed (or onion sets), bulb onions range from the pungent varieties used for dried soups and onion powder to the mild and hearty sweet onions, such as the Vidalia from Georgia or Walla Walla from Washington that can be sliced and eaten on a sandwich instead of meat.
- Multiplier onions – May refer to perennial green onions, or to onions raised from bulbs which produce multiple shoots, each of which forms a bulb. The second type is often referred to as a Potato onion.
- Tree onion or Egyptian onion - Produce bulblets in the flower head; a hybrid of Allium cepas.
- Welsh onion – Sometimes referred to as green onion or spring onion, although these onions may refer to any green onion stalk.
- Leek
Onion field during harvest, Vale, Oregon (USA).
Top Ten Onions Producers — 2005
(1000 tonnes) India9,793 China5,500 United States3,346 Turkey2,220 Pakistan1,764 Russia1,758 South Korea1,750 Japan1,637 Egypt1,302 Spain1,149World Total64,101Source:
UN Food & Agriculture Organisation (FAO)[22]The Onion Futures Act, passed in 1958, bans the trading of futures contracts on onions in the United States, after farmers complained about alleged market manipulation at the Chicago Mercantile Exchange. It provideseconomists with a unique case study in the effects of futures trading on agricultural prices. It remains in effect as of 2009.
[edit] Aroma attributes[edit] Potential medicinal use3-mercapto-2-methylpentan-1-ol in onion was found to have an antioxidant potent which inhibites peroxynitrite induced diseases.[25]
[edit] Language
Lists of miscellaneous information should be avoided. Please relocate any relevant information into appropriate sections or articles. (April 2009)
- Onions find mention in William Shakespeare's tragedy Antony and Cleopatra IV.ii, in which the character Enobarbus, observing Antony's farewells to some of his servants, declares: "What mean you, sir,/To give them this discomfort? Look, they weep;/And I, an ass, am onion-eyed: for shame,/Transform us not to women."
- In French, the expression "Ce n'est pas tes oignons" (literally: "It's not your onions") means that a topic is none of the listener's business. (In the 1990 Reforms of French orthography, the spelling oignon was officially "corrected" to ognon.)[26]
- Expressions referring to "layers of the onion" evoke the process of peeling back the layers of something (a person, reality, etc.), without however reaching a core - the centre of the onion being simply another layer. The metaphor is thus used to challenge the notion that there is a core/essence "underneath" surface layers, stressing the continuity between layer and core. Due to the number of layers in an onion it can also be used simply to evoke complexity; something having "many layers," or "always another layer behind this one."
Red onion
Onion fields near Elba, New York
Onions cooked in a frying pan
Onion weighing and packing in The Netherlands
Cut onion
Spring onion
See alsoNotes
- ^ "Allium cepa Linnaeus". Flora of North America. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200027457.
- ^ Grubben, G.J.H. & Denton, O.A. (2004) Plant Resources of Tropical Africa 2. Vegetables. PROTA Foundation, Wageningen; Backhuys, Leiden; CTA, Wageningen.
- ^ Daniel Zohary and Maria Hopf, Domestication of plants in the Old World, third edition (Oxford: University Press, 2000), p. 198
- ^ "Genetics Teaching Vignettes: Elementary School". 2004-06-15. http://genetics-education-partnership.mbt.washington.edu/class/elem.htm. Retrieved 2008-01-28.
- ^ a b "Onions Allium cepa". selfsufficientish.com. http://www.selfsufficientish.com/onion.htm. Retrieved 2006-04-02.
- ^ a b "About Onions: History". http://www.onions-usa.org/about/history.php. Retrieved 2008-01-30.
- ^ "Human Foods that Poison Pets". http://www.petalia.com.au/Templates/StoryTemplate_Process.cfm?Story_No=257#ct-4. Retrieved 2008-01-30.
- ^ "World's Healthiest Foods". Whfoods.com. 2006-06-06. http://www.whfoods.com/genpage.php?tname=foodspice&dbid=45. Retrieved 2009-09-04.
- ^ "Onion and garlic use and human cancer. (The American Journal of Clinical Nutrition)". Ajcn.org. 2006-11-01. http://www.ajcn.org/cgi/content/abstract/84/5/1027. Retrieved 2009-09-04.
- ^ Simoons, Frederick (1998). Plants of life, plants of death. Univ of Wisconsin Press. p. 568. ISBN 0299159043. http://books.google.com/books?id=KEUAbrBoeBAC&pg=PR11&lpg=PR11&dq=Plants+of+life,+plants+of+death+++bibliography&source=bl&ots=x1P06LAlHP&sig=hQsAKHTQMdX__CWBjCFwLCUod6E&hl=en&ei=PhdcSr6gD4HesQPY0vmrCg&sa=X&oi=book_result&ct=result&resnum=1. Retrieved 2009-07-13.
- ^ "Product Review: Mederma for Scars". Dermatology.about.com. http://dermatology.about.com/od/skincareproducts/gr/MedermaReview.htm. Retrieved 2009-09-04.
- ^ "Topical scar modification: Hype or help?. (Aesthetic Surgery Journal)". Linkinghub.elsevier.com. http://linkinghub.elsevier.com/retrieve/pii/S1090820X05001093. Retrieved 2009-09-04.
- ^ Zurada JM, Kriegel D, Davis IC (2006). "Topical treatments for hypertrophic scars.". Journal of the American Academy of Dermatology 55 (6): 1024–1031. doi:10.1016/j.jaad.2006.03.022. PMID 17097399.
- ^ K. Augusti, Therapeutic values of onion (Allium cepa L.) and garlic (Allium sativum L.), Indian J Exp Biol 34 (1996), pp. 634–640.
- ^ Saulis, Alexandrina S. M.D.; Mogford, Jon H. Ph.D.; Mustoe, Thomas A. M.D. (2002). "Effect of Mederma on Hypertrophic Scarring in the Rabbit Ear Model". Plastic and Reconstructive Surgery 110 (1): 177–183. doi:10.1097/00006534-200207000-00029.PMID 12087249.
- ^ "Onion Compound May Help Fight Osteoporosis". 2005-04-11. http://www.sciencedaily.com/releases/2005/04/050411112150.htm. Retrieved 2008-01-30.
- ^ Chemical & Engineering News Vol. 85 No. 35, 1 Sept. 2008, "Letters", p. 7
- ^ a b c d "Onion a day keeps doctor away? (funded by the New York State Department of Agriculture and Markets)" (hmtl). Cornell University. 2004-10-07. http://www.news.cornell.edu/releases/Oct04/onions.cancer.ssl.html. Retrieved 2008-01-30.
- ^ a b Scott, Thomas. "What is the chemical process that causes my eyes to tear when I peel an onion?". Ask the Experts: Chemistry. Scientific American. http://www.sciam.com/article.cfm?id=what-is-the-chemical-proc. Retrieved 2007-04-28.
- ^ "FAQ". Onions-usa.org. http://www.onions-usa.org/about/faq.php#cooking. Retrieved 2009-09-04.
- ^ Staunton, Margot (2008-02-01). "news.com.au, Scientists create 'no tears' onions". News.com.au. http://www.news.com.au/story/0,23599,23144566-23109,00.html. Retrieved 2009-09-04.
- ^ http://faostat.fao.org/site/340/default.aspx[dead link]
- ^ Widder, Sabine et al. (2000). "3-Mercapto-2-methylpentan-1-ol, a New Powerful Aroma Compound". Journal of Agricultural and Food Chemistry 48 (2): 418 – 423. doi:10.1021/jf9908291.
- ^ Granvog, Michael et al. (2004). "Quantitation of the Intense Aroma Compound 3-Mercapto-2-methylpentan-1-ol in Raw and Processed Onions (Allium cepa) of Different Origins and in Other Allium Varieties Using a Stable Isotope Dilution Assay". Journal of Agricultural and Food Chemistry 52 (10): 2797 – 2802. doi:10.1021/jf049874l.
- ^ Rose, Peter et al. (2003). "Inhibition of peroxynitrite-mediated cellular toxicity, tyrosine nitration, and α1-antiproteinase inactivation by 3-mercapto-2-methylpentan-1-ol, a novel compound isolated from Allium cepa". Biochemical and Biophysical Research Communications 302 (2): 397 - 402. doi:10.1016/S0006-291X(03)00193-1.
- ^ D.E. Ager, Language policy in Britain and France, p. 121 ff.