It may not do any favors for your dating life, but piling on the onions can help protect your brain. A recent study showed that certain chemical compounds found in onions may help protect the brain from stroke damage. Onions are known to contain antioxidants that can remove free radicals (which are especially hard on your brain). Onions also have polyphenols, which are linked to improved cerebral blood flow and metabolism, and other flavonoids that help protect the brain against toxins. And onions are full of vitamin C, vitamin B6, and folate, nutrients that help protect your brain. So, apologize to your date and crunch an onion.