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Onions are an antioxidant, anti-inflammatory, anticancer and pro-heart powerhouse that come in various colors and types. Here are five of the vegetable's important contributions to health
Vegetables are a crucial source of health and nutrition. There are, however, a few standout veggies, and onions -- a staple in many American kitchens and cuisines worldwide -- have offered some of the most outstanding benefits for many generations.
The type of onion may clue you in on its specific benefits. Red onions are known to be particularly rich in quercetin, a plant pigment or flavonoid present in many fruits, vegetables and grains. Found in a great variety of foods as well as beverages like tea and wine, flavonoids have antioxidant, anti-inflammatory and anti-carcinogenic properties, along with an ability to modulate cellular enzyme function.[i]
Other varieties such as green, brown and white boast their own sets of health benefits. Green onions, also commonly known as scallions, are traditionally used to treat colds, flu, abdominal pain, headache and heart disease.[ii] Let's have a look at five impressive health benefits of onions.
1. Support Heart Health
Onions contain antioxidants that may support healthy cholesterol levels as well as help manage blood pressure, both of which may lower the risk of heart disease.
A study involving 70 overweight individuals with high blood pressure found that quercetin-rich onion extract, 162 milligrams (mg) per day in particular, notably pushed down systolic blood pressure by 3 to 6 mmHg versus a placebo.[iii]
Another study conducted in 54 patients with polycystic ovarian syndrome (PCOS) concluded that eating about 40 to 50 grams (g) per day of raw red onions (if overweight) and 50 to 60 g a day (if obese) for an eight-week period slashed total and LDL cholesterol, compared to a control group, which ate smaller amounts of onions.[iv]
2. Fight Oxidative Stress
Specifically, anthocyanins, which are special plant pigments that give red onions their color, have been associated with a lower likelihood of heart attacks. This was found in a study of 93,600 women with the highest intake of anthocyanin-filled foods.[vi] Additionally, anthocyanins offer protective effects against certain kinds of cancer.[vii]
In a 2012 study, quercetin displayed a protective effect against sodium fluoride-induced oxidative stress in the heart in an animal model.[viii] Consuming onion peel itself, found to contain quercetin in abundance, may also benefit obese individuals as a way to reduce oxidative stress to help prevent the onset of chronic disease.[ix]
3. Improve Skin and Hair Health
Onion extract gel may be useful for wound healing, showing promise in improving the cosmetic appearance of postsurgical scars.[x] A study showed that it significantly improved scar softness, redness, texture, as well as appearance at the excision site at weeks four, six and 10 during the research.
Applied topically, crude onion juice may assist in hair regrowth compared to tap water, potentially serving as an effective topical therapy for patchy alopecia areata.[xi]
4. Provide Anticancer Benefits
Onions contain the flavonoid antioxidant quercetin, which may inhibit the growth of tumors.[xii] In a 2006 study, a uniquely large data set from southern European populations showed an inverse association between the frequent consumption of allium vegetables, particularly onions and garlic, and the risk of several common cancers.[xiii]
Allium vegetables also surfaced in an analysis of a Northeast Chinese population and were linked to a reduced risk of colorectal cancer in both men and women.[xiv]
5. Help Fight Diabetes
Consuming onions may also bring about helpful effects on diabetics by helping lower blood sugar levels. A study in 42 Type 2 diabetics, for instance, showed that consuming 3.5 ounces of fresh red onion decreased fasting blood sugar levels by 40 mg/dl after four hours.[xv]
Quercetin, combined with hesperidin, may also play an effective role in the regulation of insulin metabolism in diabetes.[xvi] Justifying their strong antioxidant properties, garlic, white onion and purple onion display antidiabetes as well as antihypertensive properties.[xvii]
Quercetin also shows promise for preventing neurodegeneration in diabetic retinopathy, a severe complication of the disease and a leading cause of blindness in adults worldwide.[xviii] Discover additional onion health benefits and quercetin wellness benefits on GreenMedInfo.com.
[ii] Young Sung Y et al "Aqueous and ethanolic extracts of welsh onion, Allium fistulosum, attenuate high-fat diet-induced obesity" BMC Complement Altern Med. 2018 Mar 20;18(1):105.
[iii] Brull V et al "Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial" Br J Nutr. 2015 Oct 28;114(8):1263-77. Epub 2015 Sep 2.
[iv] Ebrahimi-Mamaghani M et al "Effects of raw red onion consumption on metabolic features in overweight or obese women with polycystic ovary syndrome: a randomized controlled clinical trial" J Obstet Gynaecol Res. 2014 Apr;40(4):1067-76. Epub 2014 Mar 10.
[vi] Cassidy A et al "High anthocyanin intake is associated with a reduced risk of myocardial infarction in young and middle-aged women" Circulation. 2013 Jan 15;127(2):188-96.
[vii] Lin B et al "Effects of anthocyanins on the prevention and treatment of cancer" Br J Pharmacol. 2017 Jun;174(11):1226-1243. Epub 2016 Oct 25.
[viii] Nabavi S et al "Protective effect of quercetin against sodium fluoride induced oxidative stress in rat's heart" Food Funct. 2012 Feb 8. Epub 2012 Feb 8.
[ix] Kim K et al "Antioxidative Activity of Onion Peel Extract in Obese Women: A Randomized, Double-blind, Placebo Controlled Study" J Cancer Prev. 2015 Sep ;20(3):202-7.
[x] Draelos Z. "The ability of onion extract gel to improve the cosmetic appearance of postsurgical scars" J Cosmet Dermatol. 2008 Jun;7(2):101-4.
[xi] Sharquie K et al "Onion juice (Allium cepa L.), a new topical treatment for alopecia areata" J Dermatol. 2002 Jun;29(6):343-6.
[xii] Hashemzaei M et al "Anticancer and apoptosis-inducing effects of quercetin in vitro and in vivo" Oncol Rep. 2017 Aug; 38(2): 819-828.
[xiv] Wu X et al "Allium vegetables are associated with reduced risk of colorectal cancer: A hospital-based matched case-control study in China" Asia Pac J Clin Oncol. 2019 Feb 20. Epub 2019 Feb 20.
[xv] Eldin I et al "Preliminary Study of the Clinical Hypoglycemic Effects of Allium cepa (Red Onion) in Type 1 and Type 2 Diabetic Patients" Environ Health Insights. 2010; 4: 71-77. Epub 2010 Oct 14.
[xvi] Dokumacioglu E et al "The Effects of Hesperidin and Quercetin on Serum Tumor Necrosis Factor-Alpha and Interleukin-6 Levels in Streptozotocin-induced Diabetes Model" Pharmacogn Mag. 2018 Apr-Jun;14(54):167-173. Epub 2018 Apr 10.
[xvii] Oboh G et al "Inhibitory Effect of Garlic, Purple Onion, and White Onion on Key Enzymes Linked with Type 2 Diabetes and Hypertension" J Diet Suppl. 2018 Mar 9:1-14. Epub 2018 Mar 9.
[xviii] Ola M et al "Neuroprotective effects of quercetin in diabetic rat retina" Saudi J Biol Sci. 2017 Sep ;24(6):1186-1194. Epub 2016 Dec 3.