Onion, Allium cepa

The kitchen onion is a type of leek that is at home in every kitchen in the world and has been cultivated as a medicinal, spice and vegetable plant for more than 5,000 years. The health benefits of onions have been known for a long time: “Let your food be your medicine”, once recommended the Greek physician Hippocrates (approx. 460-370 BC). The Romans also used onions as a source of strength on their campaigns. In Russian folk medicine, it was considered ‘curative for seven ailments’ and the German healer Hildegard von Bingen (1098-1179) recommended the onion ‘for those who suffer from shaking colds or have fever or gout’. A versatile crop with a variety of uses – one of the reasons why the onion is the most widely cultivated vegetable in the world.

The onion under the magnifying glass

The kitchen onion used to be part of the lily family (Liliaceae), but according to the more recent classification, it belongs to the independent onion or leek family(Alliaceae) within the asparagus family(Asparagales). The 260 or so species also include chives, garlic, leeks and spring onions.

Onions reproduce sexually via cross-fertilisation or asexually via daughter plants. Leaves sprout from the base of an onion forming a bulb (more than one in the case of shallots) as a storage organ. The outer husks dry out and serve as a protective cover. In the vegetation period that follows after, a leafless stem up to 120 cm long grows from this, at the tip of which is a spherical false umbel of over a hundred greenish-white individual flowers. The bulbous plant can be cultivated in a wide range of climatic conditions, from colder climes to the tropics. It likes sunny and airy conditions and grows best when it receives sufficient daylight. A mild climate without temperature extremes or excessive rain is also ideal for it. There are both summer and winter bulbs. Depending on whether they are planted as seeds, onion sets or sprouted plants, the bulbs are harvested after three to six months, as soon as the foliage dies back.

Shallots are also onions. While the latter are large and round with yellow-brown, white or red skins, shallots tend to be somewhat smaller and elongated and vary in color from red to pink to brown. In addition, shallots grow in bunches, whereas the common onion grows individually on the plants.

An extraordinary resumé

The history of the onion dates back to ancient times. From its region of origin in Central Asia (its domestication is currently believed to have started in present-day Pakistan, Afghanistan and Iran), the onion quickly spread to many regions and cultures. There are sources that mention the onion as a popular cultivated plant as early as 5000 years ago. In China, for example, and then in Egypt, they were a firmly established part of the people’s diet.

An inscription on the pyramid of Giza shows that the workers building the pyramids around 2500 BC were given rations of garlic and onions to strengthen their bodies and protect them from infectious diseases. The Romans also recognized the value of onions and so the easy-to-cultivate bulbous plants spread across the entire European continent in the centuries around the birth of Christ. The onion was primarily used as a medicinal plant, for example in the monastic medicine of the European Middle Ages. It was used to treat various ailments such as plague, cholera and scurvy. The well-known physician Paracelsus also used it as a remedy in the 16th century. As a food crop, however, the onion was a typical ‘poor man’s food’, for a population that could not afford expensive food, medicines or visits to the doctor.

There is hardly a country or region in the world today where onions and garlic are not systematically cultivated. According to the FAO, over 110 million tonnes of onions and shallots were harvested in 2022, of which over 26 million tonnes were harvested in India, followed by China with over 24 million tonnes.

Delicious and healthy – the onion is an all-rounder

With over a hundred different edible varieties, the kitchen onion is very versatile. They are eaten as a vegetable and can be used as a seasoning for almost all dishes. Most onions taste very sharp, hearty and intense when eaten raw. Fried, roasted or otherwise processed with heat, they change their taste and can even become sweet.

Onions are a good source of nutrients with few calories and, like almost all vegetables, are rich in fibre, which is important for the health of our digestive system. The fact that onions are so healthy is not only due to the vitamins C, B6 and B7, but also to the minerals potassium, calcium, phosphorus, iron, iodine and selenium they contain. The essential oils in onions help to reduce bacteria and inhibit the spread of fungi, while their sulphur compounds have an antibacterial effect. Onion extracts, decoctions and ointments are used to treat illnesses such as coughs, earaches and skin problems. The abundant flavonoid antioxidants, which play a role in lowering blood pressure and cholesterol as well as in the fight against cancer, also have an anti-inflammatory effect.

In essence, the stronger the onion flavour, the healthier it is, and when it is eaten raw it is the health effects are the strongest. But beware: many people get flatulence from onions. The reason for this is so-called fructans, which are used by onions as a source of energy but are indigestible for humans. They are broken down in the intestine by bacteria, which produce air in the process, leading to flatulence.

The onion – a reason to laugh!

Onions are real superfoods – even though they have nothing to do with the expensive and highly traded foods that are often labeled as such. What’s more, organic onions are usually very cheap and available almost everywhere all year round from regional production, so they should not be missing from the menu.

Onions are also a major player in vegan cuisine. They are particularly tasty as a seasoning vegetable in all hearty dishes such as vegetable stir-fries, stews, with ‘soy meat’, in soups, salads and spreads or in marinades and simply roasted.

Sources

Federal Statistical Office

FAOSTAT

Vegpool: Superfood onions

Planet Wissen: Bulbous plants