Onion: 14 properties, benefits and nutritional values

Have you ever wondered why your eyes cry when you cut an onion? The reason is that the membrane that contains the ACSO is perforated by releasing these sulfur components into the air. The onion is so widely used in culinary dish from almost all parts of the earth. No doubt there are different types of onions – but here, we are talking about the most common ones.

  • Yellow onions – they have ivory white flesh that is surrounded by a heavy brown skin. They have a strong aroma and sulfur.
  • White onions – they have a dull white skin and are milder and sweeter than their yellow counterparts.
  • Red onions – they are light and sweet enough to be eaten raw. The outer skin and flesh are a deep magenta.
  • Shallots – They are smaller and darker and have purple flesh.
  1. An ally for strong and healthy bones

Onions have positive effects on bone health because they promote a greater density of minerals in the bones , which reduces the risk of fractures. A study carried out on a sample of female subjects shows how the increase in onion consumption is proportional to the increase in bone density, with a possible 20% reduction in the risk of fractures to the pelvis, compared to those who do not take it at all .One of the mechanisms responsible for the bone strengthening benefits deriving from onions could be the GPCS peptide, which helps to inhibit bone breakage, reverse its damage due to corticosteroids and prevent osteoporosis ( 1 ).

  1. Reduces the risk of arthritis and asthma

The fabulous anti-inflammatory properties of the onion make it one of the best vegetable choices if you suffer from painful inflammatory diseases such as arthritis or asthma. In fact some of the most important antioxidants present in the onion include flavonoids such as quercetin and anthocyanins. While anthocyanins (the same antioxidants found in red fruits) are responsible for the intense color of red onions, Quercetin is an antihistamine phytonutrient that is often found in products for treating allergies.

It reduces the effects of histamine on the immune system and inhibits leukotrienes, prostaglandins and histamines which are the cause of inflammation and their causing pain and swelling.

  1. The defense against respiratory infections

Some experts assure that certain phytonutrients present in onions increase the immune defenses , fighting inflammation of the respiratory system by reducing mucus in the nasal cavities, in the lungs and thus speeding up the healing process.

  1. A natural anti-tumor support

According to several clinical studies, the onion helps to reduce the risk of developing certain types of cancer such as colon, ovary and mouth cancer, thanks to the rich amount of antioxidants that act to prevent cellular damage ( 2 ).

Studies show that the sulfur components of onions prevent the development and growth of tumors by protecting cells from mutations and inducing apoptosis (the process of programmed cell death).

  1. Cardiovascular protection

Onions have fibronolytic benefits, meaning they provide cardiovascular protection, reducing the risk of blood clots forming. In addition, they protect against bad cholesterol, limiting the activity of harmful free radicals inside the blood vessels, thereby lowering the levels of oxidative stress and improving circulation and pressure.

  1. Prevention and treatment of diabetes

A Korean study explains how onion extract can help fight diabetes because the intake of this vegetable is effective in reducing the concentration of glucose in the blood and body weight and in preventing insulin resistance.

In addition, onions contain a rare mineral in food, chromium, an essential trace element that is also useful in managing blood sugar levels and in controlling and preventing diabetes ( 3 ).

  1. A natural aid to fertility

Antioxidants have a big impact on the vital parameters of seminal fluid, so onions, rich in them, are considered a natural method for increasing fertility. A study carried out on rats shows that the administration of high doses of onion increases the total testosterone level significantly and improves sperm concentration, viability and mobility ( 4 ).

  1. Protects the eyes

The sulfur contained in the onions stimulates the production of a protein called glutathione, a powerful antioxidant agent that has been shown to be useful in preventing macular degeneration. In addition, the onions possess a certain amount of selenium, and in one study the ability of onion juice to inhibit conjunctivitis and blepharitis was discovered.

  1. Useful for teeth and oral cavity

Onions contain thiosolfinates and thiosulfonates (also known as sulfur compounds) capable of helping to counteract bacteria capable of causing damage to the teeth.

The best way to consume onions is raw, as cooking destroys most of these components.

  1. Improves brain health

Some research suggests that onion extracts, including di-n-propyl trisulfide, can better memory, and that it can positively influence the hippocampus, that part of the brain responsible for spatial navigation and long-term memory.

  1. Natural remedy for acne

The anti-microbial, antibacterial and anti-inflammatory potential of onions are particularly useful for protecting the skin from the bacteria responsible for many skin infections, including acne itself. In the past they were also used to reduce the visibility of pimples.

Our advice is to dilute a tablespoon of fresh onion juice to one of olive oil, but you can also use almond oil, agave, flax in your preference. Apply it gently to the face, being particularly careful not to come into contact with the eyes.

And for the treatment of acne scars, you can use onion extract. Or you can look for creams that have onion extract as one of the ingredients.

  1. Rich in useful vitamins for the skin

Onions contain vitamins A , C and E, all capable of contributing positively to skin health, protecting it from premature aging caused by free radicals.

  1. Combat the effects of aging

The real antiage effectiveness attributed to onions is given by the presence of phytochemicals rich in sulfur. Not surprisingly, it is a bulb vegetable increasingly used in cosmetics, but there are natural remedies that we can simply use with onion juice. We massage the affected skin with fresh onion juice to promote blood circulation and give it brightness and vitality.

  1. Stimulates hair regrowth

Onion juice is a good way to promote hair growth thanks to the presence of sulfur, also present in amino acids.

But above all, keratin is necessary to have strong and healthy hair. Sulfur can also stimulate the production of collagen – which, in turn, helps in the production of healthy skin cells and hair growth (by default, also the treatment of hair).

The use of onion juice on hair and scalp can increase blood supply to hair follicles, increasing hair growth. It can also give you voluminous hair. In one study, participants who washed their hair with onion juice experienced more hair growth than those who did not, however, more research is needed.

Nutritional values ​​and calories:

Although some onion varieties are sweeter and therefore lighter in taste (such as shallots or golden onions), their red and white sisters contain a greater percentage of beneficial components. According to some research, golden onions contain higher levels of quercetin and sulphurous components, while red onions are richer than other protective antioxidants as indicated by their color.

The sweetest onions are left in the subsoil longer before being harvested, so that many of their carbohydrates have time to turn into sugars. Some research suggests that the nutritional benefits of onions improve as long as they are left in the soil. However, in general, although their taste softens over time, the phytonutrients are reduced. The rule of “the more the taste and smell are intense, the more nutrients are present”.

A chopped and raw medium sized onion contains about:

  • 64 calories
  • 2 grams of protein
  • 2 grams of fiber
  • 7 grams of sugar
  • 8 mg. Vitamin C (20% RDA)
  • 0.2 mg. Vitamin B6 (10% RDA)
  • 0.2 mg. Manganese (10% RDA)
  • 22 mg. Folate (8% RDA)
  • 234 mg. Potassium (7% RDA)
  • 46 mg. Phosphorus (5% RDA)
  • 0.07 mg. Vitamin B1 – Thiamine (5% RDA)
  • Contains no fat.


The onion, along with other plants such as leeks and garlic, belongs to the genus ALLIUM, a genus of the liliaceae family. All members of this genus contain therapeutic oils that have sulphurous components partially responsible for its unmistakable smell and taste.

Onions could have been one of the first subjects subject to cultivation, thanks to their easy adaptation to different types of climate and soil, their duration, ease of transport and the fact that they are much less perishable than other foods of the time. They can also be grown throughout the year, dried and stored for a long time, which in the past made them a valuable source of nutrients during times of famine.

Ancient peoples believed that onions had a beneficial effect in the treatment of various diseases and that they should therefore be an integral part of the diet. Although there is no evidence to indicate the exact appearance of the onions, their history dates back to 5000 years ago in the areas of Iran and western Pakistan. However, the use for food and medicine purposes has been around the world for thousands of years.

There is evidence of the existence of onions in parts of China, India and Egypt around 3500 BC.

In Egypt, onions were considered objects of veneration and prayer. Even depicted on the inner walls of tombs and pyramids, they symbolized eternity for their curious “circle in the circle” structure.

Finally, nourishment for the Israelites, the onion is mentioned as one of the biblical foods along with cucumbers, leeks, melons and garlic.

To date, the third largest supplier of onions is the United States, preceded only by China and India.

Cook and preserve the onions

Research shows that onions, unlike for example apples, spinach and berries, are actually one of the vegetables less contaminated by pesticides and therefore those that store less residues.

We can keep the onions for about a month away from light and heat before they start to rot so there is no disadvantage to buying a nice supply when we are at the supermarket.

With regard to conservation we give you advice. When stored close to potatoes, onions tend to absorb a gas called ethylene produced by their neighbors. It will cause them to break down at a higher speed. So the advice is to always store these two foods separately.

Onions should not be kept in the refrigerator, but once cut, they should be refrigerated and consumed as soon as possible to keep their precious nutrients intact. Close the cut parts in an airtight container, separating them from other foods. Their strong smell and taste could affect that of the rest of the foods.

Depending on the recipe, different varieties of onion are used. Red onions and shallots can be eaten raw, while white and golden onions are better suited to cooking. However, the type of onion chosen does not matter; keep in mind that a high percentage of phytonutrients is found right under the thin outer skin. To maximize the effects, just get rid of the outer paper-like layer and use up the rest.

Studies show that by cutting onions and leaving them 10 minutes in the air, their phytonutrients actually increase and become more easily absorbed. So when you cook, take some time and let them rest on the cutting board before adding them to your recipes.

Contraindications and warnings:

Onions tend to cause unpleasant reactions to those suffering from digestive problems (gastroesophageal reflux, acidity). If you notice this type of reaction when you consume onions, you may need to limit consumption or eliminate them from your diet for a certain period of time to see if the symptoms disappear or are reduced. Some individuals are able to effectively digest only small amounts of cooked onions so some tests are needed to test your personal food tolerance. Valid alternatives to red, white and golden onions are leeks, spring onions and chives that tend to cause less digestive disturbance with a similar beneficial effect and similar flavors to your recipes.

by Abdullah Sam
I’m a teacher, researcher and writer. I write about study subjects to improve the learning of college and university students. I write top Quality study notes Mostly, Tech, Games, Education, And Solutions/Tips and Tricks. I am a person who helps students to acquire knowledge, competence or virtue.

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