1. Onions contain nutritional protein, crude fiber, sugar, but also rich in a variety of vitamins and calcium, phosphorus, iron, selenium, as well as a variety of amino acids and caffeic acid, citric acid, quercetin, sulfide and so on; in addition, onions also contain prostaglandins and activation of the active ingredient of hemolyzed fibrin. 1 medium onion about 0.25mg of prostaglandin A, which can increase renal It can increase renal blood flow and urine volume, promote the excretion of sodium, potassium, is conducive to lowering blood pressure, increase coronary artery blood flow, prevent the formation of blood clots. Therefore, it is recommended that "three high" patients eat onions every day.

2. Each 100 grams of fresh onions containing about 88 grams of water, protein 1 to 1.8 grams, fat 0.3 to 0.5 grams, carbohydrates 5-8 grams, 0.5 grams of crude fiber, 130 kilojoules of calories, 12 milligrams of calcium, 46 milligrams of phosphorus, 0.6 milligrams of iron, vitamin C14 milligrams, 0.5 milligrams of nicotinic acid, 0.05 milligrams of riboflavin, 0.08 milligrams of thiamine. Carotene 1.2 mg. It also contains caffeic acid, erucic acid, cinnamic acid, citrate, polysaccharides and a variety of amino acids. Volatile oil is rich in allicin, mercaptan, trisulfide and so on. Flower buds, pollen and anthers contain carotenoids. Tear-causing component of onion is cyclic allicin, onion contained within the S-propenyl-L-semi-dirty acid sulfide is the precursor of cyclic allicin, in alkaline conditions, can be ring synthesized cyclic allicin.

3. The trace element selenium contained in onions is a strong antioxidant, which can remove free radicals in the body, enhance cell vitality and metabolism, with anti-cancer and anti-aging effects.

Onions contain some calcium. Scientists have found that eating onions can improve bone density and help prevent osteoporosis.

Onions contain phytobactericides such as allicin, and thus have a strong ability to kill bacteria.