Updated: Jul 29, 2020
Onions are native to Asia and the Middle East and have been cultivated for over 5,000 years. The Egyptians highly regarded onions and used them as currency to pay the workers who built the pyramids. They also placed onions in the tombs of kings so that they could carry these gifts bestowed with spiritual significance with them to the afterlife.
Onions have been revered throughout time, not only for their culinary use but also for their therapeutic properties. As early as the 6th century, onions were used as a medicine in India.
Onions, like garlic, are members of the allium family, and both are rich in sulfur-containing compounds that are responsible for their pungent odors and for many of their health-promoting effects. To truly receive the health benefits of onions, it is recommended to consume them on a daily basis.
Nutrient Profile: Onions contain a rich concentration of polyphenols (flavonoids, quercetin). In general, red onions are higher in total flavonoids than white and yellow onions. Onions are a very good source of biotin. They are also a good source of manganese, vitamin B6, copper, vitamin C, dietary fiber, phosphorus, potassium, folate and vitamin B1.
Vascular benefits: Research specifically focused on onions has mostly been conducted on animals rather than humans. In animal studies, there is evidence that onion's sulfur compounds may work in an anti-clotting capacity, thereby helping to prevent unwanted clumping of platelet cells. There is also evidence showing that the sulfur compounds in onions can lower blood levels of cholesterol and triglycerides and also improve cell membrane function in red blood cells.
Support for bone and connective tissue: Human studies have shown that onions can help increase our bone density and may be of special benefit to women of menopausal age who are experiencing loss of bone density.
Anti-inflammatory benefits: Onions' antioxidants (mainly quercetin) provide anti-inflammatory benefits by preventing the oxidation of fatty acids in our body. When we have lower levels of oxidized fatty acids, our body produces fewer pro-inflammatory messaging molecules, and our level of inflammation is kept in check.
Cancer protection: Onions have repeatedly been shown to lower the risk of several cancers (colorectal, laryngeal and ovarian), even when consumed in moderate amounts (once or twice a week).
Selection and Storage: Choose onions that are clean, well shaped, and which feature crisp, dry outer skins. Avoid those that are sprouting or have signs of mold. In addition, onions of inferior quality often have soft spots and dark patches, which may all be indications of decay. Onions should be stored in a well-ventilated space at room temperature, away from heat and bright light. With the exception of green onions, do not refrigerate onions.
The length of storage varies with the type of onion. Those that are more pungent in flavor (yellow onions), should keep for about a month if stored properly. They will keep longer than those with a sweeter taste, since the compounds that confer their sharp taste help to preserve them. Scallions should be stored in a plastic bag in the refrigerator where they will keep for about one week. Store cut onions in a sealed container and use them within a day or two since they tend to oxidize and lose their nutrient content rather quickly.
Maximizing the Nutrients in Onions: The flavonoids in onions tend to be more concentrated in the outer layers of the flesh. To maximize their health benefits, peel off as little of the fleshy, edible portion as possible when removing the onion's outermost paper layer. Even a small amount of "overpeeling" can result in unwanted loss of flavonoids.
When onions are simmered to make soup, their quercetin (a flavonoid) does not degrade, but, rather, it gets transferred into the water part of the soup. By using a low-heat method for preparing onion soup, you can preserve the health benefits of onions that are associated with this key flavonoid.
Eye Irritation: Use a very sharp knife and always cut onions while standing, which assures that your eyes will be as far away as possible from the onion. Consider cutting onions by an open window or by a blowing fan. Eye irritation can be avoided by cutting onions under running water. Refrigerating the onions before use reduces the enzyme reaction rate and thus lessens the potential for irritation. If cutting onions really makes you cry, consider wearing glasses or goggles.
Recipe Suggestion: I love this kale and quinoa salad from Smitten Kitchen. It is flavorful, crunchy and super healthy! There are scallions in the recipe that add a nice flavor. Enjoy!