The Many (Unknown) Health Benefits of Onions


The overlooked and much maligned onion has been around since ancient times and was most likely a dietary staple of our prehistoric ancestors.  It is often avoided because of its pungent odor and taste, along with the after effect of “onion” breath. The strong smell and taste come from the sulphur-containing compounds in onions which are also responsible for the amazing health benefits in onions.

Onions don’t usually get the spotlight for being a glamorous and trendy ‘superfood’, but surprisingly enough, the humble onion is most definitely a superfood in its own right. You know the saying, “An apple a day…”, well it should be, “An onion a day keeps the doctor away!

Onions are in the same family of root vegetables as garlic (a known superstar), shallots, leeks and scallions. They are a great source of B vitamins, especially B6, B1, folate, and biotin. They also contain copious amounts of vitamin C, manganese, copper, phosphorus, potassium and a massive amount of phytonutrients and antioxidant polyphenols. Some of the standout phytonutrients include quercetin, and allyl disulphide. Onions contain even more powerful polyphenols than their cousins, garlic and leeks, as well as tomatoes, carrots and red bell peppers.

These antioxidants make onions a natural anti-histamine (similar to medicine for colds and allergies), anti-inflammatory, and antioxidant. The powerful polyphenols in onions benefit the whole body, and make them extremely effective in preventing or fighting diabetes, cancer, cardiovascular disease and neuro-muscular diseases.

One of the primary polyphenol antioxidants in onions is Quercetin. Quercetin is an anti-inflammatory ingredient that not only protects against heart disease, blood clots, hypertension, urinary disease, prostatitis, and cancer, but also is one of the most powerful and natural anti-histamines, helping to prevent or lessen allergic reactions and asthma.

According to The World’s Healthiest Foods, onions are one of the the top ten foods for quercetin content, although it varies according to the type of onion, and growing conditions. And quercetin absorption from onions in the body twice as much as other foods that contain quercetin, like green tea and apples, as reported by Dr. Mercola, according to information from Wageningen Agricultural University, Netherlands.

Anti-Cancer Medicine

The National Onion Association considers onions a major dietary anti-carcinogen. Onions, like garlic and other allium vegetables are warriors against many types of cancer including: breast, ovarian, and uterine cancers, laryngeal, esophageal, gastric, colon, renal and prostate cancers. This is due in part from the quercetin, as well as the sulphur compounds such as: diallyl disulfide (DDS), S-allylcysteine (SAC), and S-methylcysteine (SMC). Although the exact physiology is not known, it is thought that these compounds inhibit tumor growth and gene mutations, while fighting free radicals.

While ‘moderate’ (1-2 times a week), consumption of onions helps fight these cancers, the best practice is about a half cup serving or so of onions daily. It’s not really that hard to throw some green onions (scallions) into your eggs in the morning, add some sliced red onion to your salad at lunchtime and munch on fresh salsa (with onions) at dinnertime. Cooking does not take away the onion’s nutrient power, so simmering onions into your soup and cooked dishes still gives you plenty of health benefits.

Onions, like garlic, go a long way towards helping prevent heart attacks, strokes and blood clots. The sulphur compounds in onions are very efficient in preventing clumping of blood platelets which result in clots, meaning they are highly effective in preventing heart disease, strokes, and blood clots in other parts of the body (peripheral vascular disease). Allium and allyl disulphide also help to create more flexible blood vessels which result in lower blood pressure. Onions have also been shown to help lower triglycerides and LDL cholesterol, especially when eaten as part of a diet high in vegetables and fruit.

Anti-inflammatory Effects

Quercetin maintains top level status as an anti-inflammatory, along with its anti-histamine properties. This means it helps with most inflammatory conditions, including asthma, allergies, arthritis, heart disease, Alzheimer’s, cancer, and more. Onionin A, one of the sulphur compounds, inhibits macrophage formation that trigger immune reactions and inflammatory responses, helping those with autoimmune conditions as well.  If you want to read more about fighting inflammation in your body, this article shows you the #1 inflammation fighting fruit that you can eat.

Bone, Connective Tissue, Gut Health, and Diabetes Benefits

Several human studies have shown that frequent (daily) consumption of onion can actually help to increase bone density in post-menopausal women, and help prevent fractures related to osteoporosis. What’s more, the high sulphur content of onions helps to strengthen and support strong connective tissue in the body including tendons, ligaments, cartilage and collagen—and even hair.

Onions supply healthy antibacterial properties, helping to prevent everything from cavities and gum disease, to ulcers from h. pylori and food-borne illnesses. Studies have shown onions to be effective against streptococcus strains and porphyromonas gingivalis among other bacteria, especially from fresh, raw onions. So add fresh onions to your salads, salsas, and picnic food to help ensure you don’t get sick!

Onions contain a prebiotic fiber, inulin, that helps to feed and encourage the growth of healthy gut bacteria which creates a stronger immune system, assists in healthy absorption and assimilation of food, and actually helps your mood and brain function. Inulin is also thought to be responsible for helping to prevent obesity and lower your risk of diabetes.

In those with type 2 diabetes, inulin helped to improve blood sugar reactions and maintain a more stable glucose level. Another compound in onion, allium cepa, was shown to have a significant effect on lowering blood sugar in another study with rats, although more research needs to be done.

Sleep and Mood

Onions have a positive effect on sleep and mood as well, due to the folate content in them. In fact, it is thought that onions may help with depression, by decreasing the amount of homocysteine, an inflammatory agent in the body. Besides being dangerous for heart and blood vessels, excess homocysteine may also interfere with brain hormones such as serotonin, dopamine, and norepinephrine, all of which are ‘feel-good’ hormones. These hormones also have a huge effect on sleep and appetite as well.

Colds and Flu

Native Americans recognized the power of the onion to treat colds and flu and have used it for years and years. Even the World Health Organization recognizes the power of onions for coughs, congestion, bronchitis and respiratory infections. Onions have also been used for hundreds of years as a remedy for colic and vomiting.

How to Choose Onions

Different onion varieties contain different levels of nutrients and polyphenol content. Shallots have the highest level of of polyphenols, but yellow onions have the highest flavonoid content. As a general rule of thumb, like most vegetables, the brightest and deepest coloring contains the most nutrients overall, so consuming red onions will give you the biggest bang for your buck!

Be sure to choose organic onions if you can, as conventionally grown onions are often irradiated to prevent them from sprouting—which also kills some of the beneficial nutrients. And speaking of nutrients, did you know that most of those powerful antioxidants are more concentrated in the outer layers? So when you peel an onion, only peel off the outermost papery layer to avoid throwing away the best parts of the onion. I actually chop up and use even the outer layer if I am making soup.

Live to 100 with onions?

One other thing about onions… I recently read about a longevity study that surveyed a large number of centenarians (people that live to 100 and beyond), and one of the common traits they found in the survey was that centenarians seemed to eat a lot of onions!  Just further proof that onions are a powerful superfood worthy of addition to your daily meals… I like to have them in my scrambled eggs, diced up in salmon or tuna salad, and sauteed with mixed veggies at dinner!

Enjoy eating onions with other friends, so no one notices the onion breath!

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