Onions

If tears come to your eyes whenever you slice an onion, you'll be glad to know that your tears are not shed in vain. The very compounds that give onions their pungency, taste and smell have been identified as substances that may fight cancer.

Scientists believe that onions and other members of the allium family, such as garlic, leeks, chives and shallots, may be a significant dietary factor by protecting us from certain forms of cancer. The onion first attracted the attention of the scientific community in 1989 when a study was published in the Journal of the National Cancer Institute finding that people who ate the largest amount of vegetables in the onion and garlic family were less likely to develop stomach cancer than those who did not.

Onions contain as many as 150 phytochemicals. The flavonoid quercetin, an antioxidant (phytochemical) found in onions, helps eliminate free radicals in the body, inhibits low-density lipoprotein oxidation, protects and regenerates vitamin E, and helps to circumvent the harmful effects of heavy metal ions. Other sources of quercetin are tea and apples, but research shows that absorption of quercetin from onions is twice that from tea and more than three times that from apples.

Onions may also have a beneficial effect on cholesterol levels, according to some studies. Researchers found that people who eat an onion a day can raise their “good” (HDL) cholesterol, says Dr. Barry Sears in his book The Top 100 Zone Foods. Onions may also prevent the biochemical chain of events that leads to asthma and inflammatory reactions.

Onions (Allium cepa) belong to the lily family, the same family as garlic, leeks, chives, scallions and shallots.There are over 600 species of Allium, distributed all over Europe, North America, Northern Africa and Asia. The plants can be used as ornamentals, vegetables, spices, or as medicine. There are over 120 different documented uses of the Alliums.

Onion and other Allium vegetables are characterized by their rich content of thiosulfinates, sulfides, sulfoxides, and other odoriferous sulfur compounds. The cysteine sulfoxides are primarily responsible for the onion flavor and produce the eye-irritating compounds that induce lacrimation. The thiosulfinates exhibit antimicrobial properties. Onion is effective against many bacteria including Bacillus subtilis, Salmonella, and E. coli. Onion is not as potent as garlic since the sulfur compounds in onion are only about one-quarter the level found in garlic.

The Value of Onions

Onions have a variety of medicinal effects. Early American settlers used wild onions to treat colds, coughs, and asthma, and to repel insects. In Chinese medicine, onions have been used to treat angina, coughs, bacterial infections, and breathing problems.

The World Health Organization (WHO) supports the use of onions for the treatment of poor appetite and to prevent atherosclerosis. In addition, onion extracts are recognized by WHO for providing relief in the treatment of coughs and colds, asthma and bronchitis. Onions are known to decrease bronchial spasms. An onion extract was found to decrease allergy-induced bronchial constriction in asthma patients.

Onions are a very rich source of fructo-oligosaccharides. These oligomers stimulate the growth of healthy bifidobacteria and suppress the growth of potentially harmful bacteria in the colon. In addition, they can reduce the risk of tumors developing in the colon.

Cardiovascular Help

Onions contain a number of sulfides similar to those found in garlic which may lower blood lipids and blood pressure. In India, communities that never consumed onions or garlic had blood cholesterol and triglyceride levels substantially higher, and blood clotting times shorter, than the communities that ate liberal amounts of garlic and onions. Onions are a rich source of flavonoids, substances known to provide protection against cardiovascular disease. Onions are also natural anticlotting agents since they possess substances with fibrinolytic activity and can suppress platelet-clumping. The anticlotting effect of onions closely correlates with their sulfur content.

Cancer Prevention

Onion extracts, rich in a variety of sulfides, provide some protection against tumor growth. In central Georgia where Vidalia onions are grown, mortality rates from stomach cancer are about one-half the average level for the United States. Studies in Greece have shown a high consumption of onions, garlic and other allium herbs to be protective against stomach cancer.

Chinese with the highest intake of onions, garlic, and other Allium vegetables have a risk of stomach cancer 40 percent less than those with the lowest intake. Elderly Dutch men and women with the highest onion consumption (at least one-half onion/day) had one-half the level of stomach cancer compared with those consuming no onions at all.

Western Yellow, New York Bold, and Northern Red onions have the richest concentration of flavonoids and phenolics, providing them with the greatest antioxidant and anti-proliferative activity of 10 onions tested. The mild-tasting Western White and Vidalia onions had the lowest antioxidant content and lowest anti-proliferative activity. The consumer trend to increasingly purchase the less pungent, milder onion varieties may not be the best, since the onions with a stronger flavor and higher astringency appear to have superior health-promoting properties.