onion health benefits

6 Health Benefits of Onions

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Dating back to Ancient Egypt in 3,500 B.C., onions used to be considered objects of worship and symbolized eternity due to their unique layered structure.  Even to this day, paintings of onions appear on the inner walls of pyramids and other tombs.  Onions are thought to be among the earliest cultivated crops and grew in Chinese gardens as early as 5,000 years ago.  In modern times, the United States produces 6.3 billion pounds of onions per year.  Worldwide, production rises to a staggering 105 billion pounds.  China, India, the United States, Turkey and Pakistan lead production.  Onions have been long revered for their medicinal properties.  Here are a few of the many health benefits found in this nutrient-dense superfood.


Polyphenols for Immune Support

Onions are highly concentrated with an assortment of phytochemicals.  These compounds are known for their ability to trigger various healthy reactions in the body.  Polyphenols are one type of phytochemical which has antioxidant properties.  The polyphenols found in onions allow for protection against harmful free radicals.  Buildup of free radicals is associated with cancer cell proliferation and early onset aging.  Due to these antioxidant properties, the polyphenols found in onions promote a healthy and strong immune system.  Additionally, polyphenols have been shown to inhibit allergic reactions through prevention of histamine production.  Interestingly, onions have more polyphenols than garlic, leeks, tomatoes, carrots, or red bell peppers.  Onions are a great choice for satisfying the daily requirement for these health promoting compounds.



Flavonoids for Chronic Disease Prevention

Onions are packed with yet another phytochemical known as a flavonoid.  These compounds promote health in a variety of ways.  Interesting, flavonoids act as pigments in fruits and vegetables, giving them their assortment of vibrant colors.  Research has shown that these flavonoid compounds may reduce the risk of developing Parkinson’s disease, cardiovascular disease, and stroke.  In onions, the highest concentration of flavonoids can be found within the outer layers.  Knowing this, it is important to be careful not too remove too much of the edible part of the vegetable when peeling.  This way, the maximal amount of flavonoid compounds can be consumed.


Quercetin for Cancer Prevention

Quercetin is another type of phytochemical which is found abundantly in onions. It also belongs to the flavonoid group of compounds.  Quercetin has been associated with preventing cancer through its ability to inhibit the growth and division of cancer cells in certain tumors.  One study found that participants with the highest consumption of quercetin versus the group with the lowest had a 50% reduced risk of certain types of cancer.  Beyond its amazing role in fighting cancer, quercetin also reduces symptoms of bladder infections.  Additionally, it has been shown to prevent plaque accumulation within arteries and therefore leads to lower instances of high blood pressure, heart attack, and stroke.  Red onions have the highest concentration of quercetin and white onions are the lowest.  Additionally, cooking onions reduces their concentration of quercetin slightly.



Vitamin C Source

In addition to the various phytochemicals packed into onions, there are a variety of water soluble vitamins.  One cup of chopped onions provides 20% of the Daily Value of Vitamin C.  This powerful antioxidant compound has been shown to inhibit tumor growth and prevent free radical formation.  These are two essential factors in preventing and fighting cancer.  Additionally, Vitamin C plays a critical role in collagen formation which provides the structure for hair, skin and nails.  Therefore, a healthy consumption of Vitamin C promotes integrity of these structures.


Contains Sulfur Compounds for Heart Health

Onions are also packed with various sulfur compounds that contribute to good health.  Specifically, sulfur compounds play a key role in heart heath by acting as a natural blood thinner.  Sulfur compounds prevent platelets from aggregating and reduce the overall risk for heart attack and stroke.  Additionally, sulfur compounds have been shown to reduce blood vessel stiffness which often leads to cardiovascular disease.  Sulfur compounds also improve blood lipid profiles by increasing levels of HDL, “good” cholesterol and reducing LDL, or “bad” cholesterol.  In addition to their heart healthy benefits, sulfur compounds have been shown to trigger insulin production.  One study showed that people with both type I and type II diabetes who ate red onions had lower blood glucose levels for up to four hours as compared to those who did not.

heart health

Source of Biotin

Finally, onions are packed with biotin.  One cup of chopped onions provides 27% of the Daily Value.  Biotin is a B complex vitamin which plays key roles in various metabolic processes.  Specifically, biotin has an important role in helping the body to break down and utilize fats and sugars for energy.  Aside from its crucial role in metabolism, biotin also has an important role in blood sugar control which is essential for diabetics.  Finally, biotin is associated with skin health.  Deficiencies of the vitamin are associated with skin rashes.


The onion is a very popular vegetable that dates back to the early days of civilization.  Due to its wide range of health promoting properties, it is no wonder that this vegetable has grown to reach the popularity it now has today.  From its capabilities in cancer prevention to its promotion of heart health, onions are a necessary component to any healthy diet.




  1. LiveScience.com. Onions: Health Benefits, Health Risks & Nutrition Facts. 2016. Available at: http://www.livescience.com/45293-onion-nutrition.html. Accessed February 10, 2016.
  1. LD M, LD M. Onions: Health Benefits, Nutritional Information. Medical News Today. 2015. Available at: http://www.medicalnewstoday.com/articles/276714.php. Accessed February 10, 2016.
  1. Mercola.com. Onions: What’s New and Beneficial About This Vegetable. 2016. Available at: http://articles.mercola.com/sites/articles/archive/2014/04/12/onion-health-benefits.aspx. Accessed February 10, 2016.


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