Pity the poor Vidalia. She’s southern and mellow, which you might find charming in a mate, but when it comes to onions and their anti-cancer and other health benefits, the harsh northern types are far superior.

The pungent, stinky, tear-inducing qualities come from more than 50 sulfur compounds in the onions, and it’s the sulfur compounds that are so healthy–harboring the potential to lower your blood sugar, blood pressure and cholesterol, to thin your blood, to bolster your immune system and to fight cancer directly by helping your liver detox carcinogens.

Vidalias are sweet because they’re grown in the low sulfur soils of Georgia, USA.

Onions grown in high sulfur soils are the most potent, says Dr. Irwin Goldman, a researcher and prof at the University of Wisconsin who’s wild about onions and agriculture and the effects on human health. Long-storage onions–red and yellow ones grown all over the world above the 40 degree latitude line– are highest in sulfur, he says.

Onions also contain flavonoids, pigments that produce color and act as antioxidants, protecting your  DNA from damage.

And again, the red and dark yellow varieties, including the small yellow-skinned  shallots, come out on top–containing more flavonoids and exhibiting more antioxidant activity than sweet southern Vidalias and pure white onions.     

Quercetin, one of those flavonoids, has been identified as inhibiting the body’s production of VEGF (vascular endothelial growth factor), a protein produced by cells that stimulates the growth of blood vessels and thus promotes the growth and spread of tumors.  

Quercetin is highest in yellow and red onions, not white ones, and concentrates in the outer layers, including the skin. That means 1/ select the smaller onions (You’ll get less of the inner stuff), 2/ peel onions gently and 3/ throw those valuable skins into soup stocks–or at least, into your compost. 

Onions require advance prep: Cut them and then let them sit for about a half an hour, Goldman advises. That will allow the enzymes in the onions to get to work and develop the full complement of sulfur compounds, he says.

And while you’re waiting, might it be useful to stick around and inhale some of those sulfur fumes?  Funny you should ask, says Goldman. He’s been hoping to study people working at onion ring processing plants, who cry every day. Maybe they’re getting some anti-cancer and other health benefits from sulfur in the air?