Q. Are raw onions more nutritious than cooked onions?
A. Haley Hooks, a dietetic intern at Tufts’ Frances Stern Nutrition Center, answers: “Onions are nothing to cry over. These flavorful bulbs are an excellent source of healthful chemicals: vitamin C, flavonoids, antioxidants, and sulfur compounds. Onions are nutrient powerhouses, whether eaten cooked or raw; however, raw onions have higher levels of sulfur compounds.
“Why do we care about sulfur in onions? Onions form sulfur compounds through an enzymatic reaction when cut or crushed. Studies show these sulfur compounds may protect against cancer, help lower blood sugar, and reduce the production of unhealthy cholesterol in the body. These sulfur compounds may also block platelet-clot formation and promote the breakdown of blood clots, which helps to lower the risk for heart disease and stroke. Eat your onions raw for maximum sulfur content, as cooking onions significantly decreases the quantity of the compound. However, these sulfur compounds have a downside. They give the onion its pungent odor and cause you to become teary-eyed when you slice it.
“In addition to sulfur, onions have another healthy trait going for them: The outer layers contain quercetin, an antioxidant that fights harmful free radicals in the body. Scientists believe that lightly cooking onions may actually increase the concentration of this nutrient.
“So what is the bottom line? If you like the taste of raw onions, try adding sliced onion to salads, burgers or sandwiches. If you can’t stomach the pungent taste of raw onions, lightly cooked onions still provide a myriad of health benefits.”