1. Onion can prevent cancer. Because the selenium element and quercetin rich in onion are very good antioxidants, it can stimulate the immune function of human body, thus inhibiting the wind crack and growth of cancer cells, thus preventing the invasion and harm of those toxic objects to our human body. Therefore, eating more onion can prevent cancer. 2. Onions can also play an anti-aging role, because onions can control blood sugar and make the protein content in the body sufficient. Of course, they can also indirectly supplement the deficiency of human protein, thus delaying aging and thus playing an anti-aging role. 3. Eating more onions can also play a role in preventing and treating colds. Because onions are spicy in taste and have the effect of dispelling wind chill, they play a role in preventing and treating colds from the Tao, so we eat more onions especially in cold winter.