The Winner is Red Onions
A 2017 study published in Food Research International found that red onions were most effective at killing human cancer cells compared with other onions thanks to their higher levels of the antioxidants quercetin and anthocyanin. . . . All onions are potent cancer fighters thanks to their high concentrations of the antioxidants anthocyanin and quercetin. . . . . Red onions just happen to be even better at fighting cancer thanks to their high amounts of anthocyanin, which increase the effectiveness of quercetin in attacking cancer-causing free radicals.