Onions are nutrient-rich vegetables related to garlic and leeks. They're packed with vitamins, minerals, fiber, and antioxidants like quercetin. These nutrients can lower the risk of heart disease, cancer, and diabetes. Onions also support bone health, digestive health, and may help control blood sugar levels. Eating raw onions provides the most health benefits. They're versatile in cooking and can be used in a variety of dishes, adding flavor and color.