Onions contain antioxidants and compounds that fight inflammation, decrease triglycerides, and reduce cholesterol levels all of which may lower heart disease risk. Their potent anti-inflammatory properties may also help reduce high blood pressure and protect against blood clots.Onions are loaded with plant chemicals including flavonoids, which have both an antioxidant and anti-inflammatory effect. When consumed regularly and in sufficient quantity, these compounds may help protect against chronic conditions such as cancer and diabetes