Onions are highly nutritious, with a healthy dose of vitamin C, fiber, and folic acid, as well as calcium and iron. But what really makes onions special is the antioxidant quercetin, which works to slow the progress of oxidative damage to our cells and tissue.
When it comes to heart health, the quercetin in onions helps to maintain a healthy blood pressure and keep the arteries elastic and soft. It also appears to lower the level of LDL (bad) cholesterol in people at risk for cardiovascular disorders. Those benefits together go a long way toward maintaining optimal heart health.
Lower cancer risk
Regularly consuming onions is thought to detoxify carcinogens that we get in our diets. The organosulfur compounds more specifically stop potentially cancer-causing agents from metabolizing in a dangerous way. One study found that combining onions with turmeric creates a synergistic effect that reduces the ability of cancer to take hold in the intestines, greatly reducing the risk for colon cancer.
Even moderate consumption of onions provides some benefit, but researchers suggest that the more you eat, the better. Luckily, garlic seems to provide similar protection, so you can include both in your meals rather than eat an enormous amount of onion alone.
Lesser food poisoning risk
There’s a rumor going around that onions are dangerous to cut and then store because they are extremely prone to bacterial growth. The truth is actually the opposite – onions have certain compounds that are antibacterial. In fact, the juice released when an onion is cut can kill or seriously slow the growth of several types of microorganisms known to cause food poisoning.
Therefore, eating onions with your meals means that you are less likely to get sick, not more. And don’t worry about storing leftover onions. They are completely safe for about seven days when properly refrigerated.
Enhanced immune function
Quercetin is also great for blocking certain inflammatory compounds. But when it comes to immune function, the quercetin in onions gets a boost from the selenium content. Selenium is a trace mineral found in greater concentration in onions than in other foods; it is known to reduce inflammation and stimulate immune function while also preventing excessive immune response.
Cells that are deficient in selenium age faster and reproduce inefficiently. Inflammation is an immune response that attempts to isolate injured or sick areas of the body from healthy tissue, but too much inflammation causes a host of painful and dangerous conditions. Onions appear to help keep immune function in balance.
Because quercetin blocks certain allergy-causing and inflammatory compounds, it can also be extremely helpful for seasonal allergy sufferers. Rather than run straight for an antihistamine tablet, try eating some onion to stop the production and release of histamines.
It’s the histamines that cause the itchy eyes, scratchy throat, and runny nose associated with seasonal allergies. If you really can’t stand the taste of onions, there are quercetin supplements available that are certainly worth a try.
Lower diabetes risk
Scientists have known for a long time that eating onions can increase the amount of available insulin in your system after a meal. Insulin is necessary to process the sugar in food, and the allyl propyl disulphide in an onion takes up some of the available spots in the liver where insulin becomes inactivated. Therefore, more insulin remains free to manage blood sugar levels.
Type 2 diabetes occurs when insulin becomes ineffective at processing glucose, usually because there is too much sugar, too often. Eating onions regularly ensures that there is always enough available insulin to do the job without becoming overburdened. We still recommend watching your sugar intake, though.
Reduced risk of blood clots
We need our blood to clot around the site of an injury, but clots that form within veins or arteries block blood flow and can be deadly. Onions contain a compound called rutin that has been found to ward off the development of clots in thrombotic mice. (Thrombus is the technical term for clot).
Interestingly, clots that form in arteries are rich in platelets, while those that form in veins are high in fibrin. Rutin appears to be able to attack both types of clot. More human studies are necessary, but rutin may one day soon be used to create inexpensive medicine for blood clots. In the meantime, keep eating those onions.