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Onion properties

January 15, 2021
Benefits of onion

Anyone who has ever cut an onion knows that there is something very special about this vegetable. With a unique flavor and that surprising ability to make us cry, onion is the star ingredient in any kitchen. But it will not be its culinary value that conquers us in this article, but its excellent properties and its great potential as a natural remedy.

Regardless of whether it’s raw, cooked, or whether it’s white, purple, green, or yellow, onions are credited with numerous health benefits1 2 , from cold and flu protection to cancer and heart disease prevention.

Scientific evidence indicates that onion has properties :

  • Anticancerígenas
  • Antioxidants
  • Anti-inflammatory
  • Antidiabetics
  • Expectorantes
  • Immunoprotective
  • Digestive
  • Detoxifying

What are the medicinal properties of onion due to?

The answer is simple and is directly linked to its nutritional properties. Like garlic , leeks , chives and other bulbs of the Allium family, onions are rich in vitamins, minerals, sulfuric compounds, flavonoids and other phytochemicals, the intake of which has been shown to be beneficial for our body3.

  • The phytochemicals , or phytonutrients, are naturally compounds present in fruits and vegetables that can react in the human body and trigger healthy reactions.
  • The flavonoids are antioxidant pigments and anti – inflammatory action, which have been linked to a lower risk of developing serious diseases such as Parkinson ‘s and cardiovascular disease. A particularly valuable flavonoid in onions is quercetin; According to different research, this antioxidant may be related to cancer prevention, prostate health, and blood pressure control.

According to a report in the journal Phytotherapy Research , onions are among the most important sources of antioxidants in the human diet . The high antioxidant content is responsible for its distinctive sweet taste and strong aroma. It should be noted that the antioxidant activity of red or purple onion is higher than that of yellow and white onions4.

See further on: Red Onion – Properties and Nutrients That Make It So Special

  • Other healthy compounds in onion are disulfides , trisulfides , cepaenes, and vinylditines . Numerous sources, including the American National Onion Association , claim that its regular consumption helps maintain good health, in addition to offering anticancer and antimicrobial protection5 . In addition, the sulfuric compounds in onion contain several of the essential amino acids for the body. In fact, sulfur is one of the minerals that assists in the synthesis of proteins and the construction of cellular structures.6.

Allium disulfide and allyl disulfide present in onion are transformed into allicin after ingestion. Scientific findings indicate that allicin has strong properties to fight cancer and diabetes, as well as to reduce the stiffness of blood vessels and lower blood pressure levels7.

16 Benefits of onion (scientific findings)

1. Helps fight cancer

According to several clinical studies, onions can help reduce the risk of developing colon, ovarian and oral cancer thanks to their abundant supply of antioxidants ( quercetin, vitamin C ), which prevent cell damage8 . Added to this is the power of itssulfuric compounds to prevent tumor growth.

Reportedly, eating several servings of onion each week may be enough to statistically lower this risk. For example, to prevent colorectal, laryngeal and ovarian cancer, between 1 and 7 servings of onion are recommended per week.9.

A study of southern European populations, published in the  American Journal of Clinical Nutrition , observed an inverse association between the frequency of consumption of onions, or other allium vegetables, and the risk of developing several types of common cancers10.

2. Protects heart health

Many do not know that onions have fibrinolytic properties ; This means that they provide cardiovascular protection by reducing the risk of blood clots in the arteries. In addition, it has been observed that, by having antioxidant and anti-inflammatory action, its regular consumption can reduce “bad” LDL cholesterol, limit the activity of free radicals within the blood vessels, reduce oxidative stress, improve blood circulation and regulate blood pressure levels11.

Eating raw onion on a regular basis helps reduce LDL (bad cholesterol) and oxidative stress levels so that we have a healthier heart.

3. Helps maintain healthy bones

The nutritional properties of onions can promote higher bone mineral density , which translates into reduced risk of fractures. A study conducted by the  Department of Family Medicine at the University of South Carolina , in the United States, found that bone density increased in women as the frequency of their consumption of onion increased12.

4. Assists in the prevention and control of diabetes

A meta-analysis conducted by the  Plant Resources Research Institute in the United States found that onion extract can be effective in  lowering blood glucose concentrations  and facilitating body weight loss. Researchers stated that its regular consumption can help control sugar levels and prevent insulin resistance, effectively and naturally13.

Other research also indicates that onion is an important source of chromium , a mineral that is very beneficial for controlling blood glucose and preventing diabetes in many cases.14.

5. Reduces the risk of arthritis and asthma

Due to its anti-inflammatory potential , onion is one of the best bulb vegetables you can eat to prevent or alleviate conditions like arthritis and asthma.

According to the National Arthritis Foundation , quercetin contained in onions may be especially beneficial for arthritis sufferers, as it helps inhibit the action of leukotrienes, prostaglandins, and histamines15 . These substances not only cause inflammation, but worsen symptoms of pain and swelling.

This mechanism of action has also been shown to be beneficial in inhibiting the conditions that trigger asthma16.

Warning. Due to its ability to increase stomach gas production, daily or excessive consumption of onions may exacerbate asthmatic symptoms in some people17

6. Helps prevent and fight respiratory infections

Onion is highly valued in traditional medicine for its expectorant and immunostimulating properties18 . This makes it an excellent remedy for fighting mucus buildup in the nostrils and lungs, and relieving symptoms of cold, flu, or other respiratory ailments.

The vitamin C , which remains intact in the raw onion is an essential nutrient that helps strengthen our immune function.

7. May promote fertility

Antioxidants have a strong impact on sperm health parameters, so consuming onion can be a natural way to improve fertility . During a study carried out at  Azad University in Iran, where the effect of onions on fertility in rodents was investigated19 , it was found that testosterone levels, as well as sperm concentration, viability and mobility, had significantly increased in rodents that consumed large amounts of onion.

8. Promotes healthy digestion

The digestive benefits of onions are attributed to the compound inulin , a type of prebiotic fiber that serves as food for the beneficial bacteria in our intestines20 . It has also been observed that another type of fiber present in onions, oligofructose (subgroup of inulin), can prevent and relieve episodes of diarrhea. In addition, other of its compounds appear to reduce the risk of gastric ulcers, constipation, and stomach pain.

9. It is a traditional remedy for ear infection

Although more studies are needed to confirm this benefit, onion juice is known to have been used for centuries as an earache remedy, especially for its anti-inflammatory and antibacterial properties . It is a very simple remedy; It consists of heating an onion in the oven, letting it cool, extracting part of its juice and pouring just a few drops into the infected ear.

Warning. If you suspect an ear infection, always consult your doctor before using this or any other remedy.

10. Improves eye health

The sulfur present in onions has been observed to improve the health of the eye lens by stimulating the production of glutathione , a powerful antioxidant . The higher the glutathione levels in our body, the lower the risk of developing  glaucoma, cataracts and macular degeneration. According to some research, onion also helps cure common eye infections, such as conjunctivitis and blepharitis. Another study reported that onion extract can help prevent the development of corneal cloudiness21 22.

11. Promotes good dental health

Onions contain thiosulfonate and thiosulfonate, two sulfur compounds that help reduce the bacteria responsible for tooth decay . This vegetable is also rich in vitamin C, whose antioxidant action helps maintain healthy teeth23.

Although many avoid it for fear of the typical unpleasant breath, chewing raw onion helps prevent cavities and gum problems.

12. Improves the health of skin and hair

This is another good reason to include onion in our daily diet. Thanks to its content of vitamins A, C and E, regular consumption of onions protects the skin against premature aging  and the action of free radicals. It is also often used as a natural remedy ( specifically onion juice ) against dark spots and skin pigmentation.

Regarding hair care , numerous testimonials assure that onion compounds promote its growth, help eliminate dandruff and delay graying24.

Vitamin C assists in the formation of collagen, the protein responsible for the health of the skin and hair.

It may interest you: Benefits of Onion for Hair (Juice, Shampoo, Mask, Oil)

13. Protects brain health

Various researches have suggested that the antioxidant and detoxifying properties of onion help flush out harmful toxins invading the brain. Likewise, it is believed that its sulfur compounds can slow down age-related memory loss25.

14. Promotes sexual health

Onion is widely used in certain regions of the world as a natural treatment to combat sexual impotence  and erectile dysfunction in men.26.

15. May be helpful in treating and recovering from cholera

Surprisingly, it has been seen that thanks to their  antibacterial action , onions have an inhibitory effect against  V. cholerae , the bacteria responsible for cholera27.

16. Helps improve the quality of sleep

Although it is a benefit that many do not imagine, scholars point out that when beneficial bacteria in the gut digest the prebiotic fiber in onion, they multiply, improve our intestinal health and release metabolic by-products that can induce better quality sleep , help to control stress and positively influence brain function28.

Did you know…?

  1. Onion flavonoids, which are responsible for many of its health benefits, are often more concentrated in the outer layers of the bulb. That is why it is recommended to remove the least amount of skin possible, since this way its properties are better used. It is estimated that a red onion can lose approximately 20% of its quercetin content and almost 75% of its anthocyanins if it is peeled excessively.
  2. The onion can increase the benefits of the tomato. Food synergy indicates that, in some cases, eating two foods together outweighs the benefits of eating each food separately. This appears to be the case for onions and tomatoes. The sulfuric compounds in onions appear to increase the absorption of lycopene , an antioxidant in tomato, the consumption of which has been linked to a lower risk of developing cancer, heart disease, as well as conditions that affect the brain, eyes and bones. Make sure to combine both vegetables in salads, tortillas, soups, and stir fries.
  3. The reason why raw onion is so much more powerful than cooked onion is the presence of a volatile oil rich in organic sulfur compounds. These have been observed to be partially destroyed by heat during cooking.

4 Easy remedies to take advantage of the properties of onion

Onion, honey and garlic cough syrup

  1. Cut an onion into slices and place it in a clean glass container.
  2. Add 1 finely chopped garlic clove and honey to cover the slices, cover the container tightly and let it rest for at least 8 hours.
  3. After that time, the honey will have been impregnated with the compounds of onion and garlic , so it will have a more watery consistency. That means the syrup is ready and you can take 1 tablespoon to calm your cough.

Note : Over-brewing is not recommended as this syrup only has a shelf life of 2-3 days.

See later:

Red onion to shorten the duration of the cold

Although there is some debate about the effectiveness of this remedy, many claim that it does relieve cold symptoms. Just before going to bed, place several slices, or half, of a purple onion on the soles of your feet . Then cover them with the help of socks, so that the onion does not move out of place. Remove it the next morning and repeat for 2 or 3 more days.

It may interest you: Does sleeping with onion on your feet have any real benefits?

Onion juice to relieve bites

Cut a piece of onion and rub it lightly over the area of ​​the bite so that its juice helps to reduce the swelling and soothe the itch.

Note : Onion is not only used to treat insect bites, it can also be used preventively as an insecticide.

Onion juice for hair growth

The first option is to cut half an onion and rub its juice over the entire scalp , leaving it to act for at least 15-20 minutes before washing.

The second, even simpler option is to cut an onion into slices and place it in your shampoo. As the days go by, the onion will fade and release all its juice into the container.

Note : Onion shampoo usually leaves a slight odor on the hair, but this disappears once the hair is dry.

More details in: Benefits of Onion for Hair (Juice, Shampoo, Mask, Oil)

Does the onion have contraindications?

Although the consumption of onion is considered safe and the associated risks are usually minimal, some people may experience adverse effects , especially in cases of allergy or excessive consumption .

Read more about the subject in: Onion – Types, Characteristics, Properties, Contraindications and More

Learn more about onion and other bulbs!



My name is Louise Hammond, and I am the creator of this website, a place to find information about tubers, bulbs and medicinal roots. In I show the properties, benefits, characteristics, photos and images, ways of growing and how to make delicious meals from starchy vegetables.