Onion: properties: benefits

Rich in beneficial and therapeutic properties, onion is a key ingredient at the base of many recipes of our tradition. Discover the characteristics and properties of these fantastic vegetables.

Onion, whose scientific name is Allium Cepa, is a biennial vegetable relative to chives, garlic, shallots and leeks, which has always been cultivated not only for its characteristic pungent flavor, but also for the medicinal properties that distinguishes.

Onions vary in shape and color, but the most common types are white, golden and red. The flavor can range from delicate and sweet to sharp and enveloping, depending on the variety and the season. They are commonly used to flavor many recipes and can be eaten cooked, boiled, grilled, fried, roasted or raw. Let’s see what are the characteristics of the most known and used types of onions.

Onion: most common types and varieties

Onions are very popular vegetables in Italy: they are eaten raw, cooked, sweet and sour and can not be missing in the sauté. For the different preparations we usually use different varieties : let’s deepen them together.

✓ White onions

These are onions with a white skin, large and very popular for the preparation of sautées. Some white onions are used, marinated, for the preparation of typical dishes. This is the case of the white onion of Chioggia, used for example for the preparation of sardines in saor, and the white onion of Barletta, usually consumed in vinegar.

✓ Golden onions

They are the most common onions, characterized by a coppery skin. These onions are the most used because they are perfectly suited to very different recipes: in fact, suitable for sautéing, slow cooking, frying. Among the best known golden onions we certainly find the golden onion of Parma, the onion of Sermide, with a straw-yellow color typical of Lombardy and the blonde onion of Cureggio and Fontaneto, a typical product of Piedmont, with a very sweet flavor, used for the preparation of rustida, a typical dish.

✓ Red onions

Another variety of onions are the red ones, frequently used raw or to be cooked on the grill. Their flavor is in fact generally less strong and is also appreciated raw . The peel of these onions has a typical color ranging from red to purple. The best known red onion is the red onion of Tropea, a Calabrian product very widespread throughout Italy and used raw in salads or for the preparation of compotes. Other varieties to try are the red onion of Acquaviva delle sources, a slowfood presidium grown in Puglia, with red skin and white pulp, the onion of Cavasso and Val Cossa., typical of Friuli Venezia Giulia, the onion of Certaldo, grown in the village of Certaldo in Tuscany, the onion of Suasa, with the pink skin, typical of the Marche, the onion of Cannara, very common in Umbria, where the feast of Cannara, the coppery onion of Montoro in Campania and the coppery onion of Milan.

✓ Spring onions

They are onion bulbs not yet fully developed, which are generally eaten raw as their flavor is not yet pungent like that of onions. They keep for a shorter time than onions and two variants are appreciated: the white one and the red one, the latter with a sweeter flavor.

✓ Shallot

It is not a real onion but it belongs to the onion family anyway; the shallot is smaller and has a more delicate flavor. It can be used in sauteing instead of white and golden onions and is generally more digestible.

Onion, in all its varieties, has antioxidant and anti-inflammatory properties and its consumption is associated with reducing the risk of developing cancer, lowering blood sugar and better bone health. Now let’s explore all the properties of the onion and take a look at the characteristics of the main nutrients present.

Onion: calories and nutritional values

Raw onions are low- calorie, in fact they contain only 40 calories per 100 grams of edible part, they are composed of 89% water, 9% carbohydrates and only 1.7% fiber. Practically nil, however, the contribution of fats and proteins. As for micronutrients, onion contains potassium, phosphorus, B vitamins and antioxidant compounds, as we will learn more in the next paragraph. Below is the table with the nutritional values ​​of the onion.

Nutritional values ​​per 100g of onion:

  • Waterfall: 89.11 g
  • kcal: 40
  • Proteins: 1.1 g
  • Fat: 0.1 g
  • of which saturated: 0.042 g
  • Carbohydrates: 9.34 g
  • of which sugars: 4.24 g
  • Fibers: 1.7 g
  • Potassium: 146 mg
  • Soccer: 23 mg
  • Phosphorus: 29 mg
  • C vitamin: 7.4 mg
  • Choline: 6.1 mg
  • Glycemic index: 15
  • Cholesterol: 0 g

Onion: nutritional properties

As we anticipated above, the onion is rich in numerous components that give various beneficial properties. Let’s now explore the properties of the nutrients most contained in onions.

  • Fiber: onions are a good source of fiber, with a variable percentage of 0.9-2.6%, with respect to the fresh weight and depending on the type of onion. Onions are one of the main sources of fructans, prebiotic soluble fibers that are very beneficial for the health of our gastro-intestinal system, but which can give some particularly sensitive people a bit of bloating and digestive problems;
  • Vitamin C: also known as ascorbic acid, vitamin C is a very powerful antioxidant which is also well represented in onions, especially when raw. This vitamin represents an essential co-factor in the synthesis of proteins and hormones, contributes to the protection of cells from oxidative stress, to the normal function of the immune system, to the formation of collagen and to the increase in the bioavailability of dietary iron;
  • Folic acid: onions contain a fair amount of this vitamin, an essential element for correct cellular function and helps reduce both physical and mental fatigue. It also promotes tissue growth and is very important for women’s health;
  • Phosphorus: onion contains a good amount of this mineral, a structural element of teeth, bones and cells;
  • Calcium: it is the most abundant mineral in our body, essential for bones, muscles and nerves;
  • Vitamin B6: reduces the risk of homocystinuria and sideroblastic anemia, it is also involved in the synthesis of various neurotransmitters;
  • Potassium: essential mineral involved in the control of blood pressure, heart health, nerve transmission and hydro-saline exchange at the cellular level;
  • Anthocyanins: highlighted only in red onions, anthocyanins are powerful antioxidants but also pigments that give the characteristic reddish color to these onions;
  • Quercetin: flavonoid with antioxidant and anti-inflammatory action contained in good quantities in onion;
  • Sulfur compounds: these are the molecules that give onions most of their properties. These are mainly sulphides and polysulfides, which can have preventive effects against cancer, inhibit the growth of harmful microorganisms and prevent the formation of blood clots.

Onion: the health benefits

Onion has beneficial properties for the whole body. In particular, they have been shown to have antioxidant properties, an anti-inflammatory action and the ability to suppress the growth of harmful microorganisms. Let’s now explore the benefits that onion brings to health.

✓ Antimicrobial action of onions

Onions have antimicrobial properties since their consumption can suppress the growth of harmful microorganisms, such as bacteria and yeasts thanks to the action of sulfur compounds and quercetin. In particular, some studies have shown a positive effect of onion against bacteria such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Helicobacter pylori.

✓ Regulation of blood sugar

Studies carried out on animals, but also on humans, have shown that onions can lower blood sugar levels. In particular, a study would have the hypoglycemic effect of red onions in patients with type I diabetes and type II diabetes, showing that the consumption of 100 grams of raw onions per day would lead to a significant reduction in blood glucose.

✓ Bone health

Onion is also good for your bones. Animal studies have shown that the consumption of onions has protective effects against osteoporosis and would also improve bone mass. Confirming these results, a large observational study, which involved over 35 million women aged at least 50, highlighted how the regular consumption of onions is correlated with the increase in bone density and reduction. more than 20% of the risk of hip fracture compared to those who have never consumed onions.

✓ Diuretic and detox action of onion

The consumption of onions, thanks to the water content, promotes diuresis and the elimination of waste, resulting in an aid to combat water retention and a diet-friendly food. In addition, thanks to its antibacterial and anti-inflammatory properties, onion is considered a good natural remedy for cystitis.

✓ Cancer prevention

Numerous observational studies have associated increased onion consumption with reduced risk of various types of cancers such as stomach, breast, colon and prostate cancers.

✓ Cardiac health

The properties of the onion also extend to heart health. In fact, animal studies have shown that the sulfur compounds present in these vegetables have an anticoagulant action, reduce blood levels of cholesterol and triglycerides and also improve the function of the cell membrane of red blood cells.

✓ Expectorant and decongestant function

Thanks to its antibiotic, mucolytic and anti-inflammatory action, the combination of onion syrup with a little honey is the ideal grandmother’s remedy in case of respiratory diseases such as phlegm, sinusitis, pharyngitis, laryngitis, bronchitis, cough and bronchial asthma.

✓ Better sleep and mood

The folates present in onions prevent an excessive formation of homocysteine ​​in the body which, if in excess, can interfere with the production of good mood hormones (serotonin, dopamine and noradrenaline) which regulate not only the mood, but also the sleep and appetite.

How much onion to eat per day?

Onions are often used only in the preparation of sautes, but we have seen that they are rich in properties and benefits for our health. They can in effect be considered a vegetable and are among those most appreciated by children for their sweet taste. We can therefore also eat 200 grams of onion per day (about 1 or 2 medium-sized onions), if this quantity does not bother us, possibly combined with other seasonal vegetables (salad, cucumbers, tomatoes, etc.).

Raw or cooked onion: differences and which one to prefer

From a nutritional point of view, the raw onion maintains its properties at its best: with cooking some beneficial antioxidant substances are dispersed. In this regard, we suggest not boiling it to preserve the greatest amount of beneficial substances. On the other hand, the cooked onion is more digestible : if, therefore, this vegetable is not very tolerable, you can try to cook it, perhaps only for a few minutes, with steam or directly in a pan with a little water.

Onions: how to use and consume them

Onions are a very versatile food, the basis of many recipes of our tradition. Here are some simple ideas for incorporating them, raw or cooked, into your diet:

  • Make a light saute: add the water to the oil which will lower the smoke point of the fat, preventing the oil from burning, then add your onions and all the other ingredients;
  • Guacamole sauce: in a food processor, blend the onions, a few tomatoes, the avocado, a drizzle of oil, the juice of half a lime and a pinch of iodized salt;
  • Add raw onions to your salads, summer or winter. If the taste of white onion seems too strong to eat raw, try red onions or spring onions, more delicate and digestible;
  • Onions can be among the ingredients of a wholemeal sandwich;
  • With the Breme red onion you can even prepare a winter ice cream.

Onions should always be chosen firm, with dry skins, free of bruises and not sprouting. Once purchased, they can be stored for several weeks in a cool, well-ventilated and dry place (not in the refrigerator as they would mold), away from sources of heat and light. All onions must be stored away from potatoes; held together, in fact, they deteriorate faster.

Once cut, store them in the refrigerator in a sealed container and consume them in a couple of days. The diced onions can also be stored in the freezer to be used when needed in your recipes.

The onion can not only be used in cooking, but also as an aesthetic treatment: it helps to combat acne, purify the skin and improve the appearance of scars. Furthermore, its components are useful in case of insect bites: an old grandmother’s remedy recommends rubbing the freshly cut onion on the affected part for immediate relief.

Onions: contraindications and potential negative effects

Even if we are used to using it every day in the kitchen, the consumption of onion can have contraindications. In particular we remember:

  • Digestive Problems: Onions contain FODMAPs, short-chain carbohydrates that many people find difficult to digest and that can cause unpleasant digestive symptoms such as bloating, aerophagia, cramps and dysentery. In particular, those with greater sensitivity towards FODMAPs are those suffering from irritable bowel syndrome (IBS), who should strongly limit or completely avoid the consumption of onions;
  • Eye and mouth irritation: this is the most common problem that occurs when you decide to handle an onion in the kitchen and is caused by tear factors (LF), volatile gases which, through a chain reaction, are released from the onion cells when it is damaged. The tear factors, when they reach our eyes, activate specific sensors that cause a stinging sensation followed by tearing which represents the defense reaction to counteract the irritating gases. Tear factors are also responsible for the burning sensation in the mouth when onions are eaten raw, which is reduced or eliminated completely with cooking. An advice: to avoid watering, cut the onions under running water or wet the knife with cold water, you will prevent the gases from dissolving in the air!
  • Toxicity in animals: while onions are a very healthy food for us humans, they can instead be deadly for some animals, including dogs, cats and horses. The main culprits are sulfoxide and sulfide compounds, which can induce a disease called Heinz body anemia or hemolytic anemia. It is therefore essential that our 4-legged friends never consume onions in their diet!

Curiosity: raw or cooked onion? It is decidedly better to consume raw onion because the phenolic and sulfur compounds of which they are rich are not heat resistant and are slowly lost with cooking.


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