Onions are very low in calories (just 40 calories per 100 g) and fats; however, rich in soluble dietary fiber.
Phyto-chemical compounds allium and Allyl disulphide in the onion convert to allicin by enzymatic reaction when its modified leaves are distorted (crushing, cutting, etc.). Studies have shown that these compounds have anti-mutagenic (protects from cancers) and anti-diabetic properties (helps lower blood sugar levels in diabetics).
Laboratory studies show that allicin reduces cholesterol production by inhibiting the HMG-CoA reductase enzyme in the liver cells. Further, it also found to have anti-bacterial, anti-viral, and anti-fungal activities. In addition, Allicin also decreases blood vessel stiffness by releasing nitric oxide (NO) and thereby bring a reduction in the total blood pressure. Further, it blocks platelet-clot formation and has fibrinolytic action in the blood vessels. Altogether, it helps decrease an overall risk of coronary artery disease (CAD), peripheral vascular diseases (PVD), and stroke.
Onions are rich source of chromium, the trace mineral that helps tissue cells respond appropriately to insulin levels in the blood. It thus helps facilitate insulin action and control sugar levels in diabetes.
They are an also good source of antioxidant flavonoid quercetin, which is found to have anti-carcinogenic, anti-inflammatory, and anti-diabetic functions.
They are also good in antioxidant vitamin, vitamin-C and mineral manganese. Manganese is required as a co-factor for anti-oxidant enzyme, superoxide dismutase. In addition, isothiocyanate anti-oxidants in them help provide relief from cold and flu by exerting anti-inflammatory actions.
Onions are also good in B-complex group of vitamins like pantothenic acid, pyridoxine, folates and thiamin. Pyridoxine or vitamin B-6 helps keep up GABA levels in the brain, which works against neurotic conditions
