Medicinal Properties of Onion
This Humble Bulb Deserves Far More Respect Than It Currently Gets!
The onion is amongst the oldest of all cultivated plants and has its origins in Central Asia. For over 4000 years, Central Asian, Egyptian and Indian traditional systems of medicine have recognized the medicinal properties of onion, which is why it forms an inseparable part of the diet in these countries.
Along with garlic, leeks, chives, scallions, and shallots, onion is a member of the lily family and bears the scientific name Allium cepa. Today, onions are the world's second most important horticultural crop, with an annual retail value in the United States of more than $3 billion. In your garden or grocery shelf, onion is available in many forms – red, green, yellow and white.Each of these types have a different ‘flavour’ and differ in their pungency.
Onions are rich in thiosulfinates, sulfides, sulfoxides, and other odoriferous sulfur compounds. The cysteine sulphoxides like allyl sulphoxide are responsible for the onion flavour and the eye-irritation that invariably occurs when one cuts an onion. The red colour of onion is due to anthocyanin while yellow due to quercetin.
A General Tonic : Keeps You Fighting Fit!
In early America and China, wild onions were used as a treatment for cold, cough, asthma, angina and breathing problems. Today, the WHO recognizes the use of onion extracts in providing relief from asthma as well as ulcers, scars and loss of appetite [1]. Onions are carminative, melt the phlegm and oil extracted from them is volatile. Many cultures believe that onion juice rubbed all over the body, or given orally brings stamina and vitality.
It's Cool, Dude!
Onion is said to have a ‘cooling’ effect on the body. Traditional wisdom recommends higher consumption of onion for people with more ‘body heat’, such as those suffering from skin eruptions. In villages of India, onion and jaggery in water is often taken to cure fatigue after a long walk under a hot sun. It also reduces thirst and the ill-effects of a sun-stroke.
Antimicrobial : Kills Harmful Bugs
The antibacterial results from interaction of sulphur compound S-propenylcysteine sulphoxide with sulphur (thiol) groups of microbial enzymes (such as trypsin and other proteases), leading to an inhibition of microbial growth [2,3]. Onion extract was found to inhibit Streptococcus mutans, a bacterium that causes strep throat, tonsillitis, bacterial pneumonia, as well as other diseases [4]. Additionally, as they are rich in fructo-oligosaccharides, they promote growth of healthy bifidobacteria while suppressing potentially harmful bacteria in the colon.
Cardio-Protective : It's Good for the Heart!
Onions are a rich source of flavonoids, substances known to provide protection against cardiovascular disease.[5]. They possess substances with fibrinolytic activity and hence suppress platelet clumping, acting as natural anti-clotting agents. The sulphides present in onion is reported to lower blood lipids [6] and blood pressure [7,8].
Onions Fight Cancer Too!
Onion extracts, rich in a variety of sulfides, has been shown to provide some protection against tumor growth [9]. Regions where onions are grown, mortality rates from stomach cancer are about one-half the average level. Studies have shown a high consumption of onions, garlic and other Allium herbs to be protective against stomach and colon 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. It was also found that shallots and Western Yellow and pungent yellow onion varieties are particularly effective against liver cancer cells, while pungent yellow and Western Yellow varieties have the greatest effect on colon cancer cells.
Recent studies have also proved the usefulness of onions in preventing osteoporosis[10]. As scientific research progresses, more and more uses of this wonder bulb will emerge. Its time we quit associated the onion with mouth odour and tears and gave its due to this truly unique plant.
Further Reading
- WHO Monographs on Selected Medicinal Plants Volume 1(http://whqlibdoc.who.int/publications/1999/9241545178.pdf )
- Antioxidant, anti-inflammatory,and antimicrobial properties of garlic and onions, Nutrition & Food Science, 2007, Vol. 37 No. 3,. 178-183
- Inhibitory activity of essential oils of garlic and onion against bacteria and yeasts. J Food Prot. 2004 Mar;67(3):499-504.
- Garlic and onions: their effect on eicosanoid metabolism and its clinical relevance’’, Prostaglandins, Leukotrienes and Essential Fatty Acids,2000, Vol. 6 No. 2, pp. 55-73,
- Health effects and bioavailability of dietary flavonols., Free Radic Res. 1999 Dec;31 Suppl:S75-80. Review
- Hypolipidemic action of onion and garlic unsaturated oils in sucrose fed rats over a two-month period, Cellular and Molecular Life Sciences, 1982, Volume 38, Number 8 / August, 1982
- Anti-hypertensive nutraceuticals and functional foods. J Agric Food Chem. 2009 Jun 10;57(11):4485-99.
- Antioxidative and antihypertensive effects of Welsh onion on rats fed with a high-fat high-sucrose diet. Biosci Biotechnol Biochem. 2005 Jul;69(7):1311-7.
- Onion and garlic use and human cancer, American Journal of Clinical Nutrition, 2006, Vol. 84, No. 5, 1027-1032
- A gamma-Glutamyl Peptide Isolated from Onion (Allium cepa L.) by Bioassay-Guided Fractionation Inhibits Resorption Activity of Osteoclasts, J. Agric. Food Chem., 2005, 53 (9), pp 3408–3414
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