Onions & your gut health, longevity, cancer, and more!

onions & your gut health

By: Catherine Ebeling & Mike Geary
Co-author of the best-sellers:  The Fat Burning KitchenThe Top 101 Foods that Fight Aging & The Diabetes Fix

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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National Onion Association, Greely Colorado 2011. https://www.onions-usa.org/
Dorant, Van Den Brandt, Goldbohm, Sturmans, Gastroenterology, “Consumption of Onions and a Reduced Risk of Stomach Carcinoma,” 1996.
2 http://www.sciencedirect.com/science/article/pii/S0278691503003508, Antimutagenic, antioxidant and free radical scavenging activity of ethyl acetate extracts from white, yellow and red onions, Aug. 2012
Mercola, What’s new and beneficial about onions, April 2014 http://articles.mercola.com/sites/articles/archive/2014/04/12/onion-health-benefits.aspx
Onions, World’s Healthiest Foods, http://www.whfoods.com/genpage.php?tname=foodspice&dbid=45
Anya V, The Magic Onion: Things You Didn’t Know Onions Could Do, Living Traditionally, http://livingtraditionally.com/the-magic-onion-things-you-didnt-know-onions-could-do/, November 2015.
Onions, Wikipedia, https://en.wikipedia.org/wiki/Onion
Ware, Megan, RDN, LD, Onions: Health Benefits, Nutritional Information, Medical News Today, September 2015
Onion extract may improve high blood sugar and cholesterol, Science Daily News, March, 2015

About The Watchdog

Mike Geary has been a Certified Nutrition Specialist and Certified Personal Trainer for over 15 years now. He has been studying nutrition and exercise for almost 25 years, ever since being a young teenager. Mike is originally from Pennsylvania, but has fallen in love with mountain life and now resides in the picturesque mountains of Utah. Mike is an avid adventurist and when he’s not spending his time skiing, mountain biking, hiking, or paddleboarding on the lake, he has enjoyed skydiving, whitewater rafting, piloting an Italian fighter plane (seriously), scuba diving, heli-skiing, and traveling all around the world, enjoying learning about different cultures. At the age of 40, Mike now feels healthier, stronger, and more energetic than when he was 20... All because of a healthy lifestyle and great nutrition!

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  1. Excellent information, but what do you do when you have developed an intolerance to onions & garlic, as I have for over 30 years?

    • Hi Mabel, if onions and garlic don’t agree with your body then here are some other healthy food options http://www.thealternativedaily.com/foods-you-should-be-eating/

    • Like Mabel, I have a problem with onions. I’ve had a skin graph of food injected by a allergist. Onions came back as big problems for me. They make me feel groggy and disoriented, like I’m drunk for a week. They turn my gut to liquid and supercharge my bowels so that if projectile pooping were an Olympic sport, I’d be a gold medalist.
      But I love them. I try them once a year to see if things have changed. 20+ years and nothing has changed. Got any ideas how to get this super food back in my diet? I read further down that a woman uses two meds for IBS so she can eat them, but doesn’t that just negate the whole idea of cleansing your body of crap you shouldn’t be taking anyways?
      Thanks for any thoughtful replies.

  2. I cannot imagine one day without onions and garlic! For me these beautiful veggies are more precious than gold.
    In fact I have several raised gardens growing these organic beauties.
    Life without onions/garlic is like life without air.
    Maybe someday my family will thank me for putting them in all their meals?

  3. Of late, there appears to be an increase or now diagnosed fructose intolerance , of which onions and garlic seem associated. So for those increasing their intake of these and reacting in some way, they may wish to investigate a fructose issue.

  4. I have eaten Onions all my life and I knew from the start that they were the best thing for the body. I guess i eat about 5 lbs a week to 7 lbs a week. I put Onions into everything I can and that’s the way it ought to be!!

  5. I eat onions but shouldn’t because I have IBS but I just keep taking my buscopan and mebeverane and eat away at my onions.

  6. Good article.

  7. Hi Mike,

    In the past I bought your fat burning kitchen e-book and then all my possessions were burned up and lost in the Valley Fire in Lake county, Sept. 2015. Everything! This is how I became a member on your email list.

    Would you please look it up to confirm and I you agree please send me a link so I can download it again.

    Many thanks,

  8. Please give a choice to click on sending an email to friends!

  9. good to know…I love the damn things!….

  10. The overlooked and much maligned onion has been around since ancient times and was most likely a dietary staple of our prehistoric ancestors.

  11. Tremendous article on onions. I will definitely be using more and encourage others to do so. I have been using garlic in the form of a tea which has been very helpful in removing bacteria from my system. Well, onions will be added. Thanks so very much for this information on onions.

  12. Food for thought.

  13. I love onions so much that I ferment them! Do you know anything about the value of fermented onions?

    The sulphur compounds are fermented outside of your stomach, so no “onion breath” from eating fermented onions. Most fermented foods are many times more bioavailable from being fermented, really hoping you have something to say about the powerful onion!

    Thank you,

  14. How can one get rid of fungus in the blood? Thanks for your help.

  15. Interesting because I have problems with bloating and the Dr said the worst culprit is onions and garlic and I love garlic but I do bloat every time I eat them!

  16. im a vegetarian and have always eaten loads of onions. Recently I have suffered with chronic cluster headaches and was told to avoid onions. Have you heard anything where onions might be a trigger for this condition. If I avoided everything they say could be a trigger I think they would starve

  17. Good Day;
    I would like to know why most of the mornings my belly hack. Is it something I had but I change what I had but even doing that it still hack. Your help would be greatly appreciated.

    • how’s your water intake?
      a daily maintenance water intake dose in ounces is found by diving your weight in pounds by 2.
      a cup of water is @ 8.1oz

  18. Apart from all the other benefits, onions make a great poultice to relieve pain. Grate the onion and cover the inflamed area. Change once a day. Cut an onion in half, wrap it in a chux cloth and place it over your ear to relief earache. Hold it in place with a bandage or such. Best of all… When your baby has a head cold and can’t breast feed, cut up a small onion and place it in a saucer close to their cot so they breath in the fumed while asleep. This is excellent in clearing the nasal passages. I have used all these processes many times effectively.

  19. Onions can be used to make a soothing cough syrup. Finely chop one onion, and place in a bowl. Drizzle over Blackstrap Molasses (also rich in Sulphur), to completely cover the onion, and leave to stand at room temperature overnight. By morning a clear syrup will have formed on the top of the bowl, which can be sipped from a spoon as required to sooth a cough. The syrup will continue to form over a few days, so this can be continued until all the syrup is used.

  20. If onions are go great for you, why does FODMAP eliminate them???

  21. First, I love onions and garlic, but this article says, “yellow onions have the highest flavonoid content” then the article goes on to say, “consuming red onions will give you the biggest bang for your buck!”…this is confusing to a reader?

  22. I LOVE ONIONS & Garlic! Sometimes I slice up 2-3 onions, throw them into a frying pan with some olive oil and cook them till they are almost burnt! YUM! I also can’t even eat a pizza without fresh garlic included! Oh Yeah! & garlic rolls, the stinkier the better!

    Also if you readers desire to detox your bodies of TOXIC heavy metals that accumulate in your body to cause sickness and diseases, check out the website at http://www.detoxheavymetals.info

  23. Gгeat article. I’m facing many of these issues as well..

  24. All of your information is welcome.

  25. I never received my fix book cant find a telephone number to call please let me know

    • Hi Betty, the ebooks are sent out automatically to the email that is entered when you are ordering. It is not unusual for them to end up in a spam or junk folder. Search in your email for anything from [email protected]. If you do not locate them then please email our support team at [email protected] and they will be able to assist you.

  26. Put sliced onions in a bowl, Rinse with hot water (from faucet), Leave some hot water in bowel with onions, add cider vinegar & sea salt. Let stand for 5 minutes, rinse and serve in salad, or , make an “onion only salad”with EVOO, cider vinegar, and a little sea salt. Be sure to dip a piece of Italian bread in the “juice” and enjoy.

  27. Jagdish Vasantlal Jariwala

    Our Stomach is a magic box. The brain has full control over it. Eat a less but healthy balanced diet. Include green vegetables, dry fruits in your daily food habits. Exercise daily for 40 to 50 min. of your choice and walking for 30 min. 10 min of sunlight morning to get Vitamin D. Keep your words, deeds, and mind under Divine wisdom. Be Good Do Good. Be Kind and spread kindness.

  28. Okay, I have an ulcer, you got a magic food out there that will make it go away?

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