Have you ever sat in a restaurant and smelled the tantalizing sizzle of sautéed onions moving past to another table? You may wonder why you didn’t order the same thing, and resolve to get out some onions and other veggies for your next evening’s meal.

But did you know there’s a difference between all the onion varieties in the way they impact your health? Besides the fact that both red and white onions are a low glycemic food,1 a new study has determined that red onions are superior in many ways, one of the most important being the dramatic influence they had on study participants’ cancer risk. It also turns out that, among five onion varieties, red onions kill between three and four times more cancer cells than the yellow and white ones.

The Canadian study, no doubt prompted at least in part because cancer is that country’s leading cause of death, noted that the high levels of flavonoids, specifically quercetin, myricetin and kaempferol, in the five onion types were shown to “exert potential anticancer activities.” Further:

“All onion varieties exhibited antiproliferative activity similar to purified flavonoids. The cytotoxic effects of the Stanley and Fortress onion varieties were strongest among the selected cultivars.”2

What other nutritional benefits do red onions have compared to white onions? Besides being milder, one advantage is antioxidant activity, which is one reason they have a greater ability to protect against cancer. Health Extremist3 lists stomach, colorectal, oral, laryngeal, esophageal and ovarian cancers as being types the properties in red onions help reduce. In fact, stomach cancer risk was cut in half. While both red and white onions help to thin your blood, red onions are better at it due to their rich flavonoid presence.

One more bit of wisdom: The outside skins of onions contain the highest nutrients. If you should remove the two outermost layers, you’d also be removing 75 percent of the anthocyanin content, which you do not want to do. Scientists suggest eating at least one red onion per week to get the most nutritional benefit. There are numerous delicious ways to do this: Cut them up in cold salads, slice them for a colorful, zippy layer on a cheeseburger, and toss them into your sautéed veggies.