Side Effects of Eating Onions

Onions have both positive and negative health effects.
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Onions were first cultivated in central Asia, but have quickly permeated most cuisines, due to their desirable, pungent flavor. Onions are an ingredient in dips, stews, soups, salads, and sandwiches, so it's almost unavoidable you'll experience onion side effects such as indigestion and bad breath.


Having watery eyes as a result of chopping them is only one of the disadvantages of onions. Onions do have their issues, but they can also offer positive side effects that boost your health and food enjoyment.

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Aggravates Bad Breath

Onions are members of the allium family, which also includes garlic and shallots. This family of vegetables produces sulfuric chemicals which, when metabolized, show up in your bloodstream. Blood flows everywhere, so you may notice your whole body, and your sweat, may smell a bit like onions after eating them in quantity.


Your breath is another common place where the effects of onion metabolism show up, explains a paper published in the Iranian Journal of Otorhinolaryngology in March 2015. This is because the breakdown of the sulfur compounds largely occurs in the gut, and the sulfurous odor is subsequently breathed out. The bad-breath effects may be immediate, and can continue until the vegetable is fully digested.

Read more​: 5 Health Benefits of Garlic That Make It Worth the Bad Breath


Garlic, being in the same family as onions, can cause the same effect. If you want to avoid the bad breath effects of onions, avoid eating them. You can make your onion breath worse by smoking. Eating pineapples and carrots at the end of your meals can help encourage faster digestion of onions, and reduce the effects of the sulfuric compounds on your breath.

Heightens Symptoms of IBS

Irritable bowel syndrome, or IBS, is a digestive disorder that is common and confounding. It involves the large intestine, and can cause bouts of bloating, cramping, diarrhea or constipation. The condition isn't harmful to your intestines, but it sure can be uncomfortable and life-affecting. IBS affects women more often than men, and usually presents in people younger than 45.


People with IBS often have triggers, such as stress and certain foods, that make their symptoms worse. Onions can be one of these aggravating foods, explains research published in the ​Journal of Family Medicine and Primary Care​ in October 2018.


Researchers recommend that people with IBS avoid onions and garlic to help prevent uncomfortable symptoms such as flatulence and bloating. Other foods to avoid when you have IBS include alcohol, apricots, bananas, beans, Brussels sprouts, caffeine, carrots, celery, onions, pretzels, bagels, prunes, raisins and wheat germ.


Onions Trigger Acid Reflux

People with acid reflux, whether episodic, or chronic, as in gastroesophageal reflux disease (GERD), find certain foods particularly triggering of their symptoms. If you have regular heartburn or GERD, onions should probably stay off the menu.

Onion side effects can often include increased incidences of heartburn, in which stomach acid rises up into the esophagus. This causes a burning in the chest, throat pain, and the taste of stomach fluid in the back of the mouth, explains the Cleveland Clinic. This is extremely uncomfortable, and can interfere with sleep. In some cases, GERD can lead to more serious health problems, too.


Other common foods that trigger heartburn and GERD symptoms in vulnerable people include citrus fruits, garlic, fried and spicy foods, alcohol and tomato sauces. If you do experience heartburn as a result of eating onions, over-the-counter antacids can help. Frequent bouts of heartburn call for a trip to your medical care provider.

Positive Side Effects of Onions

Onion side effects aren't all bad. It turns out onions benefit men and their hormone levels. A review of studies published in Biomolecules in February 2019, showed that regular consumption of onions can increase men's testosterone levels. This is because onion consumption increases the production of luteinizing hormone, promotes nitric oxide production and enhances antioxidant effects.


The journal Molecules published research in January 2019, detailing the health-promoting effects of onions. These include phytochemical properties, such as flavonoids and organosulfur compounds. Onions also contains biological antioxidant, antimicrobial and antidiabetic properties that show promising effects on obesity, and related co-morbidities, including high cholesterol and hypertension.


Some of the bioactive compounds in onions may even play a role in modulating, or preventing, weight gain and related disease.


Read more​: OK, But What Are Antioxidants Really?

Onions also have cancer prevention properties, explains research published in the March 2015, issue of Cancer Prevention Research. The anti-cancer effects of onions seem particularly effective against cancers of the gastrointestinal tract. Sulfur-containing compounds present in onions and their relatives, such as garlic, shallots, leeks and chives, reduce the activity of specific carcinogens, and thus may modify cancer risk.

Some of these positive health effects are observed when onions are taken in supplement form, but adding them to your diet, if you can, is also a smart step.

Best Time to Eat Onion

If you have IBS, there's probably no best time to eat onion. For those with GERD, you're best off avoiding onions, but definitely avoid eating onions at night, right before you lay down or go to sleep. Laying down after meals exacerbates heartburn effects.

If you find that onion gives you bad breath that lingers, you might consider staying away from it before a big meeting, date, or event. Onion side effects on your breath can linger for, and even escalate, several hours after consumption. If you eat them for dinner, you may find you'll have bad breath effects the next morning.

Some myths persist that storing cut onion is dangerous — that somehow the onions become toxic. The National Onion Association explains that cut onions are not poisonous. You can store cut onions in the refrigerator in a sealed container for up to 7 days.

Read more:Is It Dangerous to Cut Onions a Day Before Using Them?

Onions are a vegetable and count towards your daily intake of this nutritious food group. The Academy of Nutrition and Dietetics recommends you make five half-cup servings of vegetable part of your meals every day.




Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.

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