Onions, along with leeks, garlic, chives, shallots, and scallions, make up the Allium family of vegetables, which have beneficial effects on the cardiovascular and immune systems, as well as anti-diabetic and anti-cancer effects.
Allium vegetables are known for their characteristic organosulfur compounds, similar to the ITCs in cruciferous vegetables, organosulfur compounds are released when onions are chopped, crushed or chewed.
Epidemiological studies have found that increased consumption of Allium vegetables is associated with lower risk of gastric and prostate cancers. These compounds prevent the development of cancers by detoxifying carcinogens, halting cancer cell growth, and blocking angiogenesis.
Onions also contain high concentrations of health-promoting flavonoid antioxidants, predominantly quercetin, and red onions also contain at least 25 different anthocyanins. Quercetin slows tumor development, suppresses growth and proliferation and induces cell death in colon cancer cells. Flavonoids also have anti-inflammatory effects that may contribute to cancer prevention.
We make a point to always add either raw red or green onions to whatever we are eating for lunch.