Red onions are a potent cancer-fighting food. In a new study, researchers tested five different types of onions on cancer cells and found that the pigment of red onions combined with another chemical called quercetin work to kill colon and breast cancer cells. In fact, the pigment seems to super-charge the quercetin and magnify its ‘scavenging’ properties. Next time you want to make your dinner pungent and healthy, make sure to add some red onions.