The onions are believed to be originated in Central Asia, possibly in the Iran-Pakistan region. Today, they are probably the most widely cultivated species in the Allium genus.
There are many different varieties of onions, but the most common types are red, yellow and white onions. The taste ranges from mild and sweet to very strong and spicy, depending on the variety.
The onions have been used for thousands of years as an ingredient in various dishes by many cultures around the world. They can be eaten raw, cooked, fried, dried or roasted. Onions are commonly used as a flavoring and seasoning agent in many dishes.
Apart from adding flavor and taste to dish, onions are known to offer a wide range of health benefits. Onions have been used for centuries to reduce inflammation and heal infections. Even the World Health Organization (WHO) has recognized and confirmed the onion’s ability to relieve cough, congestion, bronchitis and respiratory problems.
Onion Nutrition Facts
Onions are very low in calories and fats, but rich in soluble dietary fiber and are an excellent source of vitamin C, vitamin B6, folate, calcium, iron, and potassium, magnesium and phosphorus.
They also contain flavonoid quercetin and sulfur-containing compounds like sulfides, polysulfides, and thiosulfinates. These sulfur-containing compounds are responsible for its characteristic flavor and eye irritating compounds when the onion is cut.
The flavonoids and sulfur-containing compounds of onion have been shown to have antioxidant, antibacterial, anti-cancer, and anti-inflammatory properties.
Health Benefits of Onions
1. Fight cancer
Onion extract is rich in a variety of sulfides, which was found to suppress tumor growth. Some studies have showed that regular consumption of onions helps to reduce the risk of several cancers, such as breast cancer, colorectal cancer, prostate cancer, esophageal cancer, laryngeal cancer, stomach cancer, and ovarian cancer [1, 2].
Vitamin C present in onions is also a strong antioxidant that can reduce the presence and impact of free radicals in the body.
2. Reduce blood sugar levels
Raw onions may be beneficial in the treatment of type 2 diabetes. A study found that the sulfur compounds in onions can help to reduce the glucose levels by increasing the amount of insulin, but more research is needed .
3. Prevent cardiovascular disease
Onions are a rich source of flavonoids which provide protection against cardiovascular disease. Onions also contain thiosulfinates that act as natural blood thinners and reduce the risk of heart attack and stroke.
4. Reduce inflammation
Since onions are anti-inflammatory in nature, they can help to reduce inflammation related to arthritis and other conditions.
According to the Arthritis Foundation, quercetin in onions can inhibit inflammation-causing substances, such as histamines, leukotrienes, and prostaglandins, in rheumatoid arthritis and osteoarthritis .
5. Enhance immune system
Onions contain selenium that can boost the immune system and fight against all kinds of infections. Moreover, the quercetin content of onion also helps maintain a strong immunity by increasing blood circulation and eliminating various foreign bodies that can lead to diseases and illness.
6. Improve digestive system
Onions are rich in dietary fiber, which is good for maintaining a healthy and regular digestive system. When consumed, this fiber can support the growth of good bacteria in the intestines. It also good in treating diarrhea and constipation, thereby promoting a healthy digestion.
7. Stimulate hair growth
Onion is rich in sulfur, which is one of the essential nutrients for healthy hair growth. When applied to the scalp, the sulfur content in onion juice can strengthen the scalp and boost blood circulation, which in turn promotes hair growth.
In a 2002 study, participants who washed their hair with onion juice experienced more hair growth than those who washed it with tap water.
8. Treat acne
The antibacterial, antimicrobial, and anti-inflammatory properties of onion are effective in combating acne-causing bacteria, which improves skin clarity and prevents future breakouts.
Mix 1 tablespoon of onion juice or extract with 1 tablespoon of olive oil and apply it to your face. Leave it on for about 20 minutes and then wash it off. You can also improve the condition by consuming onions as well.
9. Treat common cold
Onion is also a great remedy for cold and flu. It has quercetin and sulfur compounds, which are beneficial for killing various cold-causing viruses.
If you are suffering from cold and cough, you can simply consume onion juice combined with one tablespoon of honey. This simple mixture can help alleviate the cold symptoms.
10. Maintain bone health
Preliminary research suggests that onions can prevent osteoporosis. According to a study from the University of Bern in Switzerland, a peptide compound in onions called GPCS can inhibit loss of bone minerals and calcium, which is effective against osteoporosis.
Another study revealed that women who ate onions regularly had 5 percent more bone mass than those who ate less. Onion consumption was also found to have a beneficial effect on the bone density of women older than 50 years .
11. Promote oral health
The sulfur compounds in onions can help eliminate the bacteria and germs responsible for tooth decay and other teeth related problems.
If you have an oral infection, chewing on raw onion for several minutes will reduce the growth of bacteria that cause the infection and help prevent tooth decay.
However, the downside of this is that it can cause bad breath. To avoid this, rinse your mouth thoroughly after consuming raw onions.
12. Maintain eye health
The sulfur in onions can also help protect the lens of your eye from cataract formation. It works by stimulating the production of a protein named glutathione, which acts as an antioxidant for the lenses of the eye.
High levels of glutathione in the body appear to protect against eye health issues like glaucoma, cataracts and macular degeneration. Moreover, the selenium in onions helps the body absorb vitamin E, which is critical to your vision.
13. Treat urinary disorders
Onion has diuretic properties, which have been shown to be useful in treating urinary disorders. For those suffering from a burning sensation during urination, drink water boiled with 6 to 7 grams of onions can relieve the symptoms.
14. Fight allergies
Onions contain quercetin, a strong natural antihistamine which has shown to be very helpful for allergies and histamine-related inflammation.
In laboratory tests, quercetin prevents immune cells from releasing histamine, the chemical that triggers an allergic reaction.
15. Relieve asthma symptoms
Asthma sufferers may also benefit from onion consumption. The presence of flavonoids in onions have a relaxing effect on the muscles of the isolated trachea which helps the patients of asthma breathe easily.
According to a 2013 study in the American Journal of Physiology, quercetin has been found to relax the airway muscles and may provide relief of asthma symptoms .
How to Select and Store Onions
When buying onions, choose the ones that are firm, well shaped, and have no opening at the neck. Fresh onions are usually covered with papery, smooth outer scales. Avoid those with soft, wet necks or bulbs as they are starting to decay.
Onions are best stored at room temperature in a well-ventilated, dry area. Ideally, place them in a wire basket or perforated bowl to allow maximum airflow. This will keep them for months. For partially used onions, wrap them tightly in plastic wrap or in a sealed container, and refrigerate. This will keep them for several days.
Additionally, you should avoid storing onions with potatoes. This is because potatoes release moisture, and a damp environment can cause onions to rot quickly.