Onion, which is called as the "queen of vegetables", has become a common vegetable in our daily life. Onion contains a large number of natural nutrients. It is not only rich in potassium, vitamin C, folic acid, zinc, , fiber and other nutrients, but also contains two special nutrients--quercetin and prostaglandin A. Because of these two special nutrients, onion has many health benefits which can not be replaced by other food.

Firstly, prevent cancer
Researchers have found out that, onions can help prevent and control various types of cancer. A French study has showed that, women who eat more onions and garlic are less likely to suffer from breast cancer than other women. The anti-cancer effect of onions comes from its rich content of selenium and quercetin. Selenium is , which can stimulate the immune response of the body, thereby inhibiting the division and growth of cancer cells. At the same time, it can also reduce the toxicity of carcinogens. And quercetin can also inhibit the activity of cancer cells, and prevent the growth of cancer cells.

Secondly, maintain cardiovascular health.
By now, onion is the only vegetable that contains prostaglandin A. Prostaglandin A can expand blood vessels and reduce blood viscosity, so it can lower blood pressure, increase the blood flow of coronary artery and prevent thrombosis. At the same time, the high content of quercetin in onion has a high biological availability. Scientists have reported that quercetin may help prevent the oxidation of low-density lipoprotein (LDL), so it has a protective effect on atherosclerosis.

Thirdly, stimulate the appetite and help digestion.
Onion contains allicin and some other spicy elements. It is this special smell that can stimulate the secretion of gastric acid and increase the appetite. Animal experiments have proved that onion can improve the tension of gastrointestinal tract and promote gastrointestinal motility, so it plays an important role in promoting the appetite. What's more, it also has significant effects on atrophic gastritis, indigestion, loss of appetite, and so on.

Fourthly, kill the bacteria and prevent cold.
Onion contains some phytoncide such as allicin, which has a strong bactericidal ability and can effectively resist the virus and prevent influenza. When this phytoncide is expelled out through the respiratory tract, urinary tract and sweat glands, it can stimulate the secretion of cell wall pipe, so it also has many other effects such as expectorant, diuretic, diaphoretic and antimicrobial, and so on.