Experts agree that onions have been cultivated for at least the last 5000 years. Both Egyptian and Indian writings detail their use as far back as 3500 B.C. Ancient Egyptians ate onions for their ability to enhance physical prowess, and buried them with ancient Pharoahs to help wake the dead. They also found use as an antiseptic, in the treatment of headaches, and for relieving the symptoms of dysentery. In modern times, onions play a key role in cooking for most cultures. More recently, studies have shown the health benefits of onions may live up to at least some of the expectations of those ancient cultures.
Onions are vegetables that are members of the allium family, which also includes garlic, shallots, chives, and leeks. This loosely defined class of plants are annuals that can be grown from either bulbs or seeds that have an above-ground, leafless stalk. Allium plants can be found growing native in countries north of the equator, but are less common in southern hemispheres.
Onions are grown in approximately 170 countries, and global production tops 160 billion pounds. Growers in the United States plant 125,000 acres in onion seeds each year, and grow 6.2 billion pounds of finished crop. The majority of this goes to domestic use, but about 550 million pounds is exported yearly. Conversely, the U.S. imports an additional 600 million pounds of onions each year. Onions are usually grown in raised beds like asparagus.
The onion most popular with U.S. consumers are traditional yellow onions, which are also called sweet onions. Spanish onions and Vidalia onions, both of which are among the sweetest yellow onions, fall into this category. Yellow onions are the sweetest of onion varieties, and are considered among the best for making caramelized onions, which further enhances their sweetness. Red onions, which are more pungent, are a distant second. Red onion recipes generally call for the onions to be served raw, or only lightly cooked, and are often served cold. White onions rank third, and are most often used in Southwest or Mexican dishes, potato salads, and white sauces. Scallions, which are actually immature onion bulbs, are popular in the northern U.S. for the green, hollow stalks which are used as a topping and garnish. By contrast, many southern recipes call for the use of the scallion bulbs in recipes in place of onions. All onions are seasonal, and those harvested during spring and summer months are sweeter, while fall and winter harvested crops are more pungent.
The nutrition in an onion is about what we’ve come to expect of most vegetables. A cup of onions contains 64 calories and 2.7-grams of of fiber, no cholesterol, and a surprising 4.9-grams of protein. Onions also contain surprisingly high levels of potassium, phosphorus, and calcium (234 mg, 46.4 mg, and 36.8 mg per cup). They are also rich sources of folic acid.
Perhaps one of the most surprising benefits of onions is how they impact gastric health. Onions have been shown to reduce the risk of gastric ulcers, as well as stomach and prostate cancer. Studies have shown that eating onions and other allium vegetables has a strong ability to protect against a variety of cancers. Although the mechanism is not understood, many scientists believe it is related to the compounds that give these vegetables their characteristic flavor, many of which are organo-sulfur compounds. Quercetin, a flavonol, is another compound found in onions that is suspected of having anti-cancer properties. These compounds are suspected of being free-radical scavengers, or may even directly attack cancer cells. Additional benefits of eating onions include mild anti-platelet activity, which means they act as a blood thinner, antimicrobial properties. Eating dried onions may even increase bone density.
There are a variety of ways to incorporate onions into recipes. They are usually added either diced, or as whole slices, which requires slicing through the onion skin. Cutting through the skin of an onion allows two enzymes to combine, releasing a gas. The gas generates small amounts of sulfuric acid when it dissolves in fluids, causing tearing (or “crying”). It can also get on your hands and be spread by touch. It’s easy to avoid this by cutting into the onion running water. Cooking will also destroy the enzymes.
Onions have been prized for millenia by cultures around the world. Despite this, today their health benefits are often overlooked by consumers, and usually for no better reason that they may give “onion breath.” Reverse this trend, and take advantage of their unique flavor and texture by looking for ways to include them in recipes, either as a main ingredient, or a garnish. And make sure everyone has a little taste too.