One medium onion has just 44 calories but delivers a considerable dose of vitamins, minerals, and fiber. Their potent anti-inflammatory properties may also help reduce high blood pressure and protect against blood clots. Onions are an excellent source of antioxidants. In fact, they contain over 25 different varieties of flavonoid antioxidants. A review of 26 studies showed that people who consumed the highest amount of allium vegetables were 22% less likely to be diagnosed with stomach cancer than those who consumed the least amount.
Eating onions may help control blood sugar, which is especially significant for people with diabetes or prediabetes. Though dairy gets much of the credit for boosting bone health, many other foods, including onions, may help support strong bones. Onions are a rich source of fiber and prebiotics, which are necessary for optimal gut health. Prebiotics are nondigestible types of fiber that are broken down by beneficial gut bacteria.