Onion is rich in allicin and dietary fiber, which can stimulate gastric juice secretion, improve appetite, promote intestinal peristalsis, and improve anorexia and dyspepsia. Onion also contains allicin, quercetin and selenium, which can kill bacteria and fight cancer. It can resist influenza virus, enhance immunity, prevent colds, inhibit the activity of cancer-causing cells and reduce the probability of malignant tumors. In addition, onion contains prostaglandin A and sulfide, which can dilate blood vessels, lower blood pressure and blood lipid, and protect cardiovascular system.