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7 Evidence-Based Health Benefits Of Onions

Onions add that extra lick of flavor to any cuisine. But these bulbs don't just taste good – they're chock-full of beneficial substances like flavonoids and alk(en)yl cysteine sulfoxides (ACSOs) which are great for your health. Onions can help with allergies and hair loss. They can also tackle high blood sugar and even lower your risk of cancer. So go ahead and make a yummy investment in your health – chop up some onions for dinner tonight!

They are a versatile dinner companion that can spice up any cuisine. But did you know onions have some serious muscle power when it comes to your health too? Like garlic, these translucent veggies belong to the lily family. Their curative power has been recognized for centuries by the Greeks, Egyptians, Romans, and Indians. An ancient papyrus from Egypt even mentions onions as a remedy for diarrhea.

Peeling An Onion

There are two chemical groups in onions that are particularly good for you: flavonoids and alkenyl cysteine sulfoxides (ACSOs). These give onions a wide range of health-boosting properties – from modulating your blood sugar to lowering the risk of cancer. Flavonoids in onions, which have antioxidant properties, are of two kinds: anthocyanins, which give some varieties of red or purple color, and quercetin and its derivatives, which give brown or yellow skins to other varieties. The ACSOs meanwhile are responsible for the distinct smell and taste of onions. They get converted into many beneficial compounds including mono-, di-, and tri-sulfides, thiosulfonates, and thiosulfinates.1 Let’s look at the health benefits of onion.

1. Helps With Diabetes

Onions can help people with diabetes, lowering the amount of insulin needed by the body and improving how it reacts to insulin. A study by Jung et al found that onion peel extracts, with its high quercetin content, can lower insulin resistance and improve how the body responds to glucose.2

Another study showed that allyl propyl disulfide (APDS), a compound found in onions, led to lower blood glucose levels and an increase in serum insulin levels in healthy adults. APDS is thought to have an insulin-sparing impact, reducing the amount of insulin needed by the body.3

2. Relieves Allergies And Asthma

Onions can counter the action of histamine, an inflammatory chemical released by the body in response to allergens. Histamine is what makes us sneeze and gives us itchy eyes and a running nose. 4 It is also found in the airways of people with asthma and is responsible for many of its symptoms.5

Thiosulfinates found in onions have anti-inflammatory properties and have the potential to be anti allergic and anti asthmatic.6

One animal study also showed that they inhibited the release of histamine and acted against bronchial obstruction caused by allergens.7

3. Kills Dental Bacteria

Owing to their antimicrobial and antibacterial properties, onions can help keep your teeth healthy. Research has found that onion extracts can kill bacteria which cause dental caries (Streptococcus sobrinus and Streptococcus mutans ) and adult periodontitis (Prevotella intermedia and Porphyromonas gingivalis).8So, adding onions to your diet can help take care of your pearly whites.

4. Protects Your Heart

The thiosulfinates that make onions so pungent are also great for your bloodstream and heart. The vegetable version of aspirin, these compounds thin blood and stop blood platelets from aggregating or clotting when there is damage to the blood vessels.The dense, pungent varieties of onions have more of these antioxidant compounds so reach out for them instead of the mild, sweet ones.9

One animal study also confirmed the hypocholesterolemic effect of red onions brought down the levels of low-density lipoprotein (LDL) or bad cholesterol, and that too without reducing the levels of high-density lipoprotein (HDL) or good cholesterol. This cholesterol lowering capacity of onions can thus help fight coronary heart disease.10

5. Lowers The Risk Of Cancer

Onion and garlic can have a protective effect against various cancers. Research has found that people who have approximately half a cup of onion per day are less likely to have cancers of the ovary, esophagus, prostate, mouth and throat, breast, colon, and kidney than those who eat little or no onion.

For instance, those who consume more onion have a 25% lower risk of breast cancer and a 56% lower risk of colon cancer as against those don’t eat onion.11

Onions can help fight against cancer in various ways: the antioxidants in onions can stop free radicals from damaging cell DNA; compounds in the onion also slow the growth of cancer cells and trigger their self-destruction; they also increase enzymes which block the action of carcinogens.12

6. Treats Hair Loss (Alopecia Areata)

Alopecia areata is a condition in which you see patchy hair loss on the scalp. A study found that the application of onion juice for six weeks led to hair re-growth in 86.9% of the participants. Men tend to benefit more than women – it was observed that 93.7% men responded positively as against 71.4% women.13

7. Fades Scars

The topical application of onion extracts can improve the appearance of scars. When scarring was studied after eight weeks of onion extract gel application in a study, it was found that overall appearance, redness, texture (smoothness), and softness were significantly better than in scars that were not treated.14

Onion In Alternative Medicine

Ayurveda too describes many properties of onions that can benefit your health:

  • It is said to stimulate the heart, reduce gastric problems such as gas and colic, and improve bile production.
  • Fresh onion juice taken with honey (or aged jaggery) is said to be a tonic for the heart.
  • Onion is considered to be an aphrodisiac, especially when combined with ginger juice, ghee, and honey.
  • Onion juice can help with nose bleeds and a runny nose when administered nasally.
  • Smelling a crushed onion can also curb nausea and vomiting.15

References   [ + ]

1. Griffiths, Gareth, Laurence Trueman, Timothy Crowther, Brian Thomas, and Brian Smith. “Onions—a global benefit to health.” Phytotherapy Research 16, no. 7 (2002): 603-615.
2. Jung, Ji Young, Yeni Lim, Min Sun Moon, Ji Yeon Kim, and Oran Kwon. “Onion peel extracts ameliorate hyperglycemia and insulin resistance in high fat diet/streptozotocin-induced diabetic rats.” Nutrition & metabolism 8, no. 1 (2011): 1.
3. Augusti, K. T., and M. E. Benaim. “Effect of essential oil of onion (allyl propyl disulphide) on blood glucose, free fatty acid and insulin levels of normal subjects.” Clinica Chimica Acta 60, no. 1 (1975): 121-123.
4. Torkos, Sherry. “Seasonal Allergies: DITCH YOUR OTCS FOR NATURAL RELIEF.” Alternative Medicine 22 (2015): 25.
5. Wilson, Andrew M. “The role of antihistamines in asthma management.” Treatments in respiratory medicine 5, no. 3 (2006): 149-158.
6. Wagner, H. “Search for new plant constituents with potential antiphlogistic and antiallergic activity.” Planta medica 55, no. 03 (1989): 235-241.
7. Dorsch, W., H. Wagner, Th Bayer, B. Fessler, G. Hein, J. Ring, P. Scheftner, W. Sieber, Th Strasser, and E. Weiss. “Anti-asthmatic effects of onions: Alk (en) ylsulfinothioic acid alk (en) yl-esters inhibit histamine release, leukotriene and thromboxane biosynthesis in vitro and counteract paf and allergen-induced bronchial obstruction in vivo.” Biochemical pharmacology 37, no. 23 (1988): 4479-4486.
8. Kim, Jung-Haeng. “Anti-bacterial action of onion (Allium cepa L.) extracts against oral pathogenic bacteria.” The Journal of Nihon University School of Dentistry 39, no. 3 (1997): 136-141.
9. Onions with a Nutritional—Not Pungent—Punch, US Department of Agriculture.2007.
10. Guan, Lei, Hau Yin Chung, Yalun Su, Rui Jiao, Cheng Peng, and Zhen Yu Chen. “Hypocholesterolemic activity of onion is mediated by enhancing excretion of fecal sterols in hamsters.” Food & function 1, no. 1 (2010): 84-89.
11. Galeone, Carlotta, Claudio Pelucchi, Fabio Levi, Eva Negri, Silvia Franceschi, Renato Talamini, Attilio Giacosa, and Carlo La Vecchia. “Onion and garlic use and human cancer.” The American journal of clinical nutrition 84, no. 5 (2006): 1027-1032.
12. Onions and Garlic For Your Health, American Institute for Cancer Research.
13. Sharquie, Khalifa E., and Hala K. Al‐Obaidi. “Onion juice (Allium cepa L.), a new topical treatment for alopecia areata.” The Journal of dermatology 29, no. 6 (2002): 343-346.
14. Draelos, Zoe D., Leslie Baumann, and Alan B. Fleischer. “A new proprietary onion extract gel improves the appearance of new scars: a randomized, controlled, blinded-investigator study.” The Journal of clinical and aesthetic dermatology 5, no. 6 (2012): 18.
15. Svoboda, Robert. Ayurveda: Life, health and longevity. Penguin Books India, 1992.

Disclaimer: The content is purely informative and educational in nature and should not be construed as medical advice. Please use the content only in consultation with an appropriate certified medical or healthcare professional.