Red Onions are a very good source of vitamin C, B6, biotin, chromium, calcium and dietary fiber. In addition, Red Onions contain good amounts of folic acid and vitamin B1 and K. Red Onions contain a large amount of sulfur and are especially good for the liver. There are various benefits that Red Onions can offer to the heart. Benefits Of Red Onions Boost beneficial HDL cholesterolThin the bloodRetard blood clottingLower total blood cholesterolLower triglyceridesLower blood pressure