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January 15, 2021
Nutritional properties of onion

Onion is a surprisingly diverse and universal food. It is enjoyed in almost all parts of the world and is included in all kinds of preparations, from homemade recipes to very select dishes. However, although it is a basic vegetable to flavor in our kitchens, the truth is that we do not know many things about it.

If you want to know a little more about onions , their types, flavors, nutritional properties, health benefits, ways of consumption, contraindications, buying and storage advice, among other topics of interest, keep reading below.

What are onions?

Onions are bulb vegetables belonging to the same family of the garlic , the onion , the onion and leek (Allium plants). Its scientific name is allium cepa and some of its other common names are big-headed onion, egg onion, or bulb onion.

Onion bulbs can vary in size, shape, color, and flavor ; The latter can range from sweet and juicy to sharp and spicy, depending on the type of onion and the season in which they are grown. But by far the most common grading system used in grocery stores is color, as it is very easy to tell the difference between red, yellow, or white bulbs.

9 Characteristics and other interesting facts about onion

  1. The onion plant has long, tubular bluish-green leaves.
  2. The bulb, which develops at the base of the plant, is the commonly used edible part of the onion.
  3. Onions are usually served cooked, but can also be eaten raw or pickled. It is very easy to incorporate them into the diet because they are extremely versatile vegetables
  4. They have been used as food for thousands of years; in ancient Egypt, they were even worshiped and used in funeral rituals.
  5. They are vegetables rich in vitamins, minerals, antioxidants and other healthy compounds. Its main health benefits include reducing the risk of obesity, heart disease, and cancer.
  6. It is estimated that more than 105 million pounds of onions are harvested each year worldwide and, according to the Food and Agriculture Organization of the United Nations (FAO), China is the largest producer on the planet . India, the United States, Turkey and Pakistan are also large producers.
  7. Chopping onion makes us cry because a sulfur-based gas is released . This gas reacts with the water in our eyes and turns into sulfuric acid. As a result, the tear ducts must work rapidly to eliminate irritation from the eyes in the shortest possible time.
  8. The diameter of these bulbs can range from less than 1 inch to more than 4.5 inches. According to the Guinness Book of World Records, the largest onion ever grown weighed 10 pounds (about 5 kilograms).
  9. There are several tricks to avoid undesirable “onion breath” , for example eating a sprig of parsley, rinsing your mouth with equal parts lemon juice and water, or chewing a citrus peel.

Types of onions

Onions show a wide diversity, hence they are classified into different types or varieties . The two most important classification systems are based on color and taste.


  • Yellow Onion : Yellow onion, also called vidalia onion, is the “standard” variety of onion in the kitchen. Its ivory-white flesh is surrounded by a thick brown skin, and it often gives off a strong sulfur aroma. If a recipe doesn’t specify what kind of onion to use, the safest bet is a yellow onion. Some yellow varieties are Slug, Big-headed Yellow , Vidalia .
  • White onion : This variety of onions has very white skin and flesh; Its slightly sweet flavor makes it an excellent choice for preparing salads, homemade guacamole, side dishes, etc. Some white varieties are Blanca Grande Tardía , Cirrus , La Joya , Sierra Blanca , Stratus , Sterling .
  • Pearl onions . The pearl onion is a type of white onion, very similar in appearance, but smaller in size and milder in taste. These characteristics make it an ideal onion for making pickles.
  • Red, red or red onion : Red onions are widely used in salads, sandwiches and other raw preparations, especially for their attractive purple color. They can have a really spicy flavor, which goes well with other strong-flavored vegetables, like kale or arugula. Some purple varieties are Carmen , Red Onion from Tropea , Red Onion from Turda , Red Granex .

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


Basically the dividing line here is between strong flavor and mild / sweet flavor. As a general rule, the softer onion varieties are milder and sweeter in taste, while the harder varieties are hot and add intensity. Sometimes this distinction between “hot / spicy” and “mild / sweet” can overshadow distinctions related to color. For example, we may hear the term “sweet onion” being used to differentiate between varieties of yellow, red or white onions.

Differences in flavor in onions can sometimes be related to geography, local weather conditions, and harvest time. For example, it is known that the pungency of onion can be influenced by factors such as the mildness of the climate and the mineral content of the soil. In some areas with heavy annual rainfall, sulfur can leach out of the soil and lead to the cultivation of sweet onions. In addition, we can hear about ” early bulb ” (sweet) or ” late bulb ” onions.”(Spicy), a terminology that refers to the speed of bulbs formation and also has an effect on the flavor of these vegetables. Another very common classification is known as “short day onions”, “intermediate day onions” and “long day onions”.

Other classifications

Onion varieties can also differ in terms of:

  • Perishable character , which is not always predictable based on color, flavor or other easily detectable differences. For example, there is a variety of red onions, called “Breme” onions, which are only grown in northwestern Italy and distributed locally due to their delicate nature. Of course, most of the onions that we find in the supermarket are not highly perishable and do not need to be used immediately, unless they are cut.
  • Bulb shape , which divides onions into globose, conical, depressed, piriform, and oblate onions, among others.
  • Place of origin , hence we have American, Spanish, French, Japanese, Italian, English and Dutch varieties.

Contrary to what many believe, bulbs such as shallots, chives or leeks are not types of onion, but other species within the same family. They are very close relatives, with a similar taste and appearance, but they do not belong to a single species.

Nutritional properties of onion

The nutrient supply of the onion is surprisingly good. It is not for pleasure that nutrition experts recommend its consumption so much. Onions are rich in vitamins such as vitamin C and various B complex vitamins (B6, B1, biotin, folate), in minerals such as manganese, copper, phosphorus and potassium, as well as in fiber and numerous phytonutrients (flavonoids, compounds of sulfur, acids).

One cup of chopped raw onion contains approximately: 1

  • Calories: 64
  • Grease: 0 g
  • Protein: 2 g
  • Fibra: 2 g
  • Azúcar: 7 g
  • Vitamina C: 8 mg (20%)
  • Vitamina B6: 0.2 mg (10%)
  • Dosage: 0.2 mg (10%)
  • Folic acid: 22 mg (8%)
  • Potasio: 234 mg (7%)
  • Phosphorus: 46 mg (5%)
  • Vitamin B1 (thiamine): 0.07 mg (5%)

Note : Percent (%) values ​​are for adults or children over 4 years of age and are based on a 2,000 calorie daily reference diet. These daily values ​​can be higher or lower depending on the individual needs of each person .

It is a very low calorie food, rich in water and with an excellent content of healthy compounds . For example:

  • Flavonoides (fisetina, quercetina, kaempferol, isoramnetina)
  • Organic acids (ferulic acid, protocatechuic acid, myristic acid)
  • Sulfur-containing compounds (dimethyl trisulfide, cysteine ​​sulfoxide, diallyl monosulfide, diallyl disulfide, onionin A)

It is recommended to include it in our diet on a daily basis to obtain all its properties , especially raw, since during cooking a part of the vitamins and minerals can be lost. The raw onion also has a higher concentration of sulfur compounds.

16 Healthy benefits: what is onion good for?

The onion, like other members of its family, has a high medicinal potential . Since ancient times it has been considered as a natural remedy against multiple health conditions, a use that has persisted to this day. It is currently said that the compounds present in onion can favor the prevention and treatment of conditions such as cancer, hypertension and diabetes2 , but, as you will see below, these are not the onlybenefits of onionto consider. It has also been observed that:

  1. Helps fight cancer
  2. Protects heart health
  3. Helps maintain healthy bones
  4. Can help prevent or control diabetes
  5. Reduces the risk of arthritis and asthma
  6. Helps prevent and fight respiratory infections
  7. May help improve fertility
  8. Promotes healthy digestion
  9. It is a remedy for ear infection
  10. Helps improve sleep quality
  11. Improves eye health
  12. Promotes good oral health
  13. Helps in the treatment and recovery of cholera
  14. Improves sexual health
  15. Protects brain health
  16. It is good for healthy hair and skin

Learn what science thinks about these and other effects of onion on the body. Keep reading on 15+ Proven Properties and Benefits of Onion .

See later:

How to select, store and use onions?


To buy good quality onions you should take into account the following tips:

  • Choose onions with clean, well-formed bulbs, firm to the touch, and with a crisp, dry, and shiny outer skin.
  • Avoid those that have soft spots, damp, moldy patches, or are germinating (an indicator of aging or poor storage).
  • Whenever possible, obtain onions that come from an organic source or a local grower to reduce the likelihood of exposure to pesticides and heavy metals.


Once you have the onions at home, you can follow these recommendations to extend their shelf life:

  • Whole onions should be stored at room temperature in a cool, dry and well-ventilated place , away from heat and bright light; in these conditions they can last up to 4 weeks.
  • Place in a hanging wire basket or perforated container with a raised base so that air can circulate underneath.
  • Avoid refrigerating them, as this will make them soft.
  • They also shouldn’t be stored under the sink because they absorb moisture.
  • All onions should be stored away from tubers like potatoes , as the moisture and ethylene gas in the potato make the onion go bad more easily.
  • In addition to proper storage, it’s important to inspect your onions regularly for any moldy or discolored bulbs.

The duration of storage usually varies depending on the type of onion. Those with a spicier flavor, such as yellow onions, can keep for about 1 month if stored correctly. In general, they stay good longer than sweeter-tasting onions, such as white onions, as the compounds that give them their strong flavor also help preserve them.

To store a cut raw onion it is advisable to place them in a sealed container. Use within a day or two at most to avoid loss of quality.

The onions cooked can better retain their flavor if stored in an airtight container. They should not be placed in a metal container because this method can cause discoloration.

Although peeled and chopped onions can be frozen, this practice can cause them to lose much of their flavor.


Onion is one of those ingredients that we can include in almost any recipe. Its flavor is highly appreciated in soups, stir-fries, salads, sauces, stews, fried foods, roasts, among many other preparations.

Some of its best culinary uses are:

  • Onion salad cut into slices and combined with other seasonal vegetables, such as tomato.
  • Sautéed onion to use as a base in the preparation of sauces, pasta, stews and soups.
  • Finely chopped onion to combine with tomato, avocado and jalapeño (guacamole sauce).
  • Caramelized onions to enhance the flavor of any recipe, especially vegetarian / vegan dishes.

Tips for getting the most out of onions

  • Several studies have observed that, cutting the onion and leaving it exposed to the air for approximately 10 minutes, increases its content of phytonutrients and makes it more absorbable for our body. Whenever you have time, chop the onions a few minutes beforehand and let them rest on the cutting board .
  • Cooking the onions briefly helps bring out their sweet flavor. The thinner the cuts, the faster they will cook; and the longer they cook, the sweeter they taste.

Recommended Video: How to Chop Onions

Is it better to eat onions raw or cooked?

It is always good to include onions in our diet, no matter if they are raw or cooked. This bulb has very special characteristics, and one of them is its low loss of nutrients during cooking or pickling. However, the healthiest variant is undoubtedly raw onion, as it contains higher levels of organic sulfur compounds; These compounds are responsible for most of its health benefits, for example its anticancer, anti-inflammatory and antibacterial effects.

One point to keep in mind is that the outer layers of the onion contain higher concentrations of flavonoids, therefore it is recommended to remove as few layers as possible while you are peeling this vegetable.3.

Contraindications and side effects of onion

Almost everyone can safely eat onion as part of a healthy and balanced diet, but it is known to cause undesirable effects in some cases due to its high content of sulfur compounds. An example of this is its irritating action on the digestive system of people with heartburn, acid reflux or poor digestion of FODMAP foods.

If symptoms of poor digestion or some kind of reaction are observed after consuming onion, it is best to eliminate it for a while to see if the symptoms disappear. It should be noted that some people are better able to digest cooked onion rather than raw onion, or they can also better tolerate other bulbs in the same family, such as leeks , chives, or scallions .

In addition to digestive discomfort, there may be other contraindications and adverse effects4 5 . For example:

  • Drastic decrease in blood sugar levels. Diabetes patients should not consume large amounts of onion, as this can cause a significant drop in their blood sugar levels.
  • Gastric burning Although onion is traditionally used to alleviate various gastrointestinal disorders, its excessive consumption can cause gastric irritation, vomiting, nausea and burning.
  • Irritation of the skin. Some people may experience irritation and rashes of the face or skin when they come in contact with onion juice. It is advisable to test it first on a small area of ​​the skin before applying it as a remedy.
  • Excess onion intake can lead to heartburn. Pregnant and lactating women should limit their consumption as they are more likely to experience this effect.
  • Drastic decrease in blood pressure. Onion can lower systolic and diastolic blood pressure. People taking blood pressure medication should consume it in moderation.
  • Anticoagulant property. The constant use of onion can inhibit the blood clotting process, hence a person taking anticoagulant medications must keep their consumption under control.
  • People who are sensitive to onions should not take aspirin and eat onions at the same time, as aspirin increases this sensitivity and can cause an allergic reaction.
  • Increase in lithium levels. Onion can decrease the body’s ability to remove lithium. Before taking any lithium medicine, it is advisable to consult a doctor to find out if you can eat onion or not.
  • Bad breath. Although it is not considered a health problem, raw onion always causes bad breath due to its high sulfur content. This effect can be very strong in people who consume raw onion on a daily basis.

Quick answers to Frequently Asked Questions

How to grow onions?

To grow your own onions, you must take into account the following general guidelines:

  • Position : Full sun.
  • Frost tolerant: Yes.
  • Soil : Sow in fertile soil, humid but well drained, free of weeds and rocks; avoid dense and clayey soils. It is always recommended to add some type of organic compost before planting to get bigger onions.
  • Spacing :
    • Individual plants : at least 15 cm apart in each direction.
    • Rows : 10 cm between plants and 20 cm between rows, at least.
  • Sowing : It is recommended to plant the onion bulbs or seedlings in spring, while the soil is still cold; Depending on the location, this can be in late fall or early spring.
  • Watering : Onions don’t need too much watering during their development.
  • Cultivation : Germination of onions usually occurs after a few days. The green stems will continue to grow over the weeks, as will the tuberous bulb underground.
  • Harvest : Your onions are ready to be harvested when the stems turn brown, begin to drop, and the onion is visibly large.

Find everything you need to know on the subject in: How to Grow Onion? Easy and Complete Grow Guide

What is the onion plant like?

The onion is a bulbous herbaceous plant that is included in the genus of the Allium . It can reach a height of approximately 15 to 45 cm and its appearance is very similar to that of other plants in its family, such as chives, shallots, leeks or chives.

  • Leaves . It has long, hollow, sheathed, pointed leaves; They are bluish-green in color and grow alternately around each other at the base of the plant.
  • Stem . Its stem is elongated, hollow and straight; it can grow between 80 and 150 cm.
  • Flowers . Onion flowers are white and grow from the flower stem or scape in an umbel structure.
  • Bulb . Storage of the plant’s food reserves initiates the formation of a multilayered bulb. The color can vary between purple, white and yellow depending on the species.
  • Roots . A bundle of small, fibrous, shallow roots extends from the underside of the bulb.
  • Seeds . The seeds of this plant are very small and shiny black in color. They have a convex side and the other flat.

What is the origin and history of onions?

Although there is no conclusive evidence, most researchers point to Central Asia as the place of origin for onions, some 5,000 years ago, specifically the area where the present-day countries of Iran and West Pakistan are located. Along with other nations, these Central Asian countries remain one of the largest onion growing regions in the world.

It is said that, because onions were less perishable than other foods of the time and that they could be easily grown throughout the year in different types of climates and soils, they became one of the first crops domesticated by man .

Some records show that onions were already cultivated in parts of China, India and Egypt around 3500 BC. In Egypt, they were even considered an object of worship and symbolized eternity due to their “circle within a circle” structure. In fact, paintings and hieroglyphs of onions have been found within the inner walls of ancient Egyptian pyramids and tombs.

Onions were also a common food for the Israelites, being described as one of the biblical foods , along with cucumbers, melons, leeks, and garlic.

Today, they are consumed all over the world. It is very difficult to find a kitchen without onions. The largest producers include China, India and the US, but it is widely grown in other regions as well.

What vitamins do onions have?

Among the most abundant vitamins and minerals in onions are:

  • Vitamina C: 8 mg (20%)
  • Vitamina B6: 0.2 mg (10%)
  • Dosage: 0.2 mg (10%)
  • Folic acid: 22 mg (8%)
  • Potasio: 234 mg (7%)
  • Phosphorus: 46 mg (5%)
  • Vitamin B1: 0.07 (5%)

Note : The percentage values ​​(%) are indicated for adults or children over 4 years of age and are based on a reference diet of 2,000 calories per day; they can be higher or lower depending on the individual needs of each person .

Onion also contains vitamin K, riboflavin (vitamin B2), niacin (vitamin B3), pantothenic acid (vitamin B5), choline, betaine, calcium, iron, sodium, zinc, copper, selenium, and fluoride.

How to avoid crying when chopping onions?

Chopping onions makes you cry because when you cut them, a sulfur-based gas is produced and released. This gas reacts with the water in our eyes and forms an acid, sulfuric acid . As a result, the tear ducts need to create profuse tearing to get rid of the irritation.

Here are some tips to avoid crying while chopping or peeling onion :

  • Try to move your face as far away from the onion as possible so that the gas disperses before reaching your eyes.
  • Put the onion in the freezer for about 5 minutes before chopping it.
  • Light a candle and place it next to the cutting board.
  • Chew gum while cutting the onion.
  • Soak the onions in cold water for about 10 minutes before cutting them.
  • Whenever possible, pick them up with an open window.

Is it good to eat raw onion?

Yes. In fact, raw onions have higher levels of vitamins, minerals, and organic sulfur compounds, which are responsible for most of their health benefits.

It should be noted that the onion does not experience a great loss of nutrients during cooking.

Is it safe to eat raw garlic and raw onion together?

Yes. Some people may have a hard time tolerating the intense flavor of these bulbs, but in general raw garlic and onion can be eaten together without any problems.

It may interest you: Garlic and Onions – The 6 Benefits You Don’t Want to Miss

How to make onion water?

Onion water is a traditional home remedy that helps treat various health conditions and brings many benefits. Its preparation is very simple .

You will need to:

  • 1 onion
  • Water (about a liter)
  • Honey to taste (optional)


  1. Peel the onion and cut it into two halves.
  2. Place the liter of water in a saucepan and add both pieces of onion.
  3. Bring to a boil; wait 3 minutes once it reaches the boiling point.
  4. Turn off the heat, cover the saucepan and let it rest for 10 minutes.
  5. Finally strain, discard the onion remains and reserve the “onion water” in a glass container. If you want, you can sweeten it by adding a little honey to improve the flavor.

Other uses of the onion-honey combination in: Onion with Honey – Say Goodbye to Cough and Hello to Nice Hair

How many onions a day is too much?

There is no specific dose that indicates the amount we should eat per day; however, overdoing it is not good. Maintaining a moderate consumption of 1 to 2 onions per day (depending on the size) is a reasonable amount.

What does onion taste like?

The taste of raw onion is difficult to describe as it feels strong, aromatic, spicy, pungent, or even bitter. In the case of cooked onion , it has an aromatic, less spicy and sweeter flavor, which is pleasant for most people.

What to do so that the onion does not chop?

Not all people like the strong and spicy taste of raw onion. If that’s the case for you, you can try some of these tricks to soften its flavor without losing its nutrients:

  • Lightly sauté the onion slices in a very hot skillet or griddle.
  • Macerate for 30 minutes, or even the night before, with olive oil or vinegar.
  • Let the chopped onion rest in a bowl with ice and lemon juice for 15 minutes.
  • Dip the chopped onion in a solution of water, sugar and salt (1 teaspoon respectively), for half an hour.

What is black onion?

The black onion is not a variety of onion as such, but a gourmet product (similar to black garlic), obtained by maturing the bulbs for several weeks. It is almost always prepared with shallots, a variety with smaller bulbs and a milder flavor.

The process consists of keeping the shallot under very controlled temperature and humidity conditions, usually 66 degrees of temperature and 80% humidity, until it reaches its unique dark appearance. This usually takes about 60-70 days.

No preservatives or additives are added in its preparation , nor do bacteria or yeast intervene. The result is an onion with a creamy texture, dark in color, with a flavor between sweet and balsamic . When the black onion has been packaged, it undergoes a pasteurization process to guarantee its food safety.

Black onion is believed to be native to Japan but is currently gaining popularity around the world, not only for its culinary value, but also for its health benefits. Some research claims that this practice doubles the antioxidant content of shallot.

In general, they are an excellent addition to salads and other preparations, they tend to be more digestive than fresh onion and they do not produce an unpleasant smell on the breath.

It may interest you: Healthy Properties of Black Garlic – What Makes It So Special?

What other names does the onion have?

Depending on the place, onions are also known as :

  • Big-headed onion
  • Egg onion
  • Bulb onion
  • Ajera onion
  • Common onion
  • Onion from Alcalá la Real
  • Chinchón onion
  • Paean onion
  • Pomegranate onion
  • Madrid onion
  • Matanzas onion
  • Murcian onion
  • Wild onion
  • Chives (young onion)
  • Chives
  • Evergreen
  • Tipula

In other languages:

  • Onion (English)
  • Ceba (Catalan)
  • Onion (Francés)
  • Onion (Galician)
  • Onion (Italian)
  • Onion (Portugés)
  • Onion (Aleman)
  • Strain (Latin)

The scientific name for onion is Allium cepa.


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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.