- “Onions are super-healthy,” said Victoria Jarzabkowski, a nutritionist with the Fitness Institute of Texas at the University of Texas at Austin. “They are excellent sources of vitamin C, sulphuric compounds, flavonoids and[phytochemicals.”
- Phytochemicals, or phytonutrients, are naturally occurring compounds in fruits and vegetables that are able to react with the human body to trigger healthy reactions. Flavonoids are responsible for pigments in many fruits and vegetables. Studies have shown that they may help reduce the risk of Parkinson’s disease, cardiovascular disease and stroke.
- Jarzabkowski explained that a particularly valuable flavonoid in onions is quercetin, which acts as an antioxidant that may be linked to preventing cancer. It has a host of other benefits, as well, according to the University of Maryland Medical Center, reducing the symptoms of bladder infections, promoting prostate health and lowering blood pressure. Other important phytochemicals in onions are disulfides, trisulfides, cepaene and vinyldithiins. They all are helpful in maintaining good health and have anticancer and antimicrobial properties, according to the National Onion Association.
- Partly because of their use in cooking around the world, onions are among the most significant sources of antioxidants in the human diet, according to a 2002 report in the journal Phytotherapy Research. Their high levels of antioxidants give onions their distinctive sweetness and aroma. These antioxidants and flavonoids may help promote heart health, reduce inflammation and decrease the risk of cancer, in addition to a load of other good things.
- “I like to recommend eating onions because they add flavor without salt and sugar,” Jarzabkowski said. Onions are low in calories (45 per serving), very low in sodium, and contain no fat or cholesterol. Furthermore, onions contain fiber and folic acid, a B vitamin that helps the body make healthy new cells.
- Onions are healthy whether they’re raw or cooked, though raw onions have higher levels of organic sulfur compounds that provide many benefits, according to the BBC. A 2005 study in the Journal of Agricultural and Food Chemistry found that there is a high concentration of flavonoids in the outer layers of onion flesh, so you’ll want to be careful to remove as little of the edible part of the onion as possible when peeling it.
- According to Jarzabkowski, onions encourage a healthy heart in many ways, including “lowering blood pressure and lowering heart attack risk.” A 2002 study in the journal Thrombosis Research suggested that sulfur acts as a natural blood thinner and prevents blood platelets from aggregating. When platelets cluster, the risk for heart attack or stroke increases. This research further supports a similar 1992 study in Thrombosis Research that focused on sulfurs in garlic. Furthermore, a 1987 animal study in the Journal of Hypertension demonstrated delayed or reduced onset of hypertension with sulfur intake. However, the authors said more research was needed to determine if this benefit might be found in humans.
- The quercetin in onions may also help prevent plaque buildup in the arteries, which reduces the risk of heart attack and stroke, according to the University of Maryland Medical Center. But since most of the studies in this regard have focused on animals, more research is needed to understand the effects in humans.
- Anti-inflammatory: Onions’ sulfurs may be effective anti-inflammatory agents, according to a 1990 study in the journal International Archives of Allergy and Applied Immunology. Quercetin has been found to relax the airway muscles and may provide relief of asthma symptoms, according to a 2013 study in the American Journal of Physiology.
- Immune system : ‘“The polyphenols in onions act as antioxidants, protecting the body against free radicals,” said Anne Mauney, a dietitian based in Washington, D.C. Eliminating free radicals can help encourage a strong immune system. According to the University of Maryland Medical Center, the quercetin in onions also reduces allergic reactions by stopping your body from producing histamines, which are what make you sneeze, cry and itch if you’re having an allergic reaction.
- Cancer: Quercetin may be a powerful anti-cancer agent, according to Jarzabkowski. The University of Maryland Medical Center said that quercetin may especially inhibit cancer cells in “breast, colon, prostate, ovarian, endometrial, and lung tumors.”
- The National Onion Association discussed a recent study from the Netherlands that showed that people who ate onions absorbed twice as much quercetin as those who drank tea, and more than three times as much quercetin as those who ate apples, which are other high-quercetin sources. Red onions are especially high in quercetin, according to the association. Shallots and yellow onions are also good options. White onions contain the least amount of quercetin and other antioxidants.
- Digestion: The fiber in onions promotes good digestion and helps keep you regular. Additionally, onions contain a special type of soluble fiber called oligofructose, which promotes good bacteria growth in your intestines. One 2005 study in Clinical Gastroenterology and Hepatology found that oligofructose may help prevent and treat types of diarrhea. The phytochemicals in onions that scavenge free radicals may also reduce your risk of developing gastric ulcers, according to the National Onion Association.
- Regulating blood sugar: The chromium in onions assists in regulating blood sugar. The sulfur in onions helps lower blood sugar by triggering increased insulin production. One 2010 study in the journal Environmental Health Insights revealed that this might be especially helpful to people with people with diabetes. People with Type 1 and Type 2 diabetes who ate red onions showed lower glucose levels for up to four hours.
- Bone density in older women:A 2009 study in the journal Menopause found that daily consumption of onions improves bone density in women who are going through or have finished menopause. Women who ate onions frequently had a 20 percent lower risk of hip fracture than those who never ate onions.
- While not especially serious, eating onions can cause problems for some people. The carbohydrates in onions may cause gas and bloating, according to National Digestive Diseases Information Clearinghouse. Onions, especially if consumed raw, can worsen heartburn in people who suffer from chronic heartburn or gastric reflux disease, according to one 1990 study in the American Journal of Gastroenterology.
- Eating a large amount of green onions or rapidly increasing your consumption of green onions may interfere with blood thinning drugs, according to the University of Georgia. Green onions contain a high amount of vitamin K, which can decrease blood thinner functioning.
- It is also possible to have a food intolerance or an allergy to onions, but cases are rare, according to an article in the Journal of Allergy and Clinical Immunology. People with onion allergies may experience red, itchy eyes and rashes if an onion comes into contact with the skin. People with an intolerance to onions may experience nausea, vomiting and other gastric discomfort.
- Lastly, Jarzabkowski encouraged people to make sure their onions are fresh. “Onions keep for a long time,” she said, “but they still spoil.”
Source: Onions: Szalay, Jessie; “Health Benefits, Health Risks & Nutrition Facts”, 16 October 2014, http://www.livescience.com/45293-onion-nutrition.html