11 Side Effects of Eating Onions

11 Side Effects of Eating Onions: Onions are one of the most problematic foods for digestive health and not only. Despite their many properties and health benefits, they remain a source of major side effects such as stomach pain and general upset, severe heartburn and allergic reactions. Because they irritate the stomach lining, result in an increase in stomach acid production and acid reflux, they constitute a trigger for asthma in individuals with the condition. Onions further irritate the eyes, throat, even bladder and existing ulcers. If you have gastritis, then eating onions is bad for you and can easily result in more severe symptoms and side effects as well as delayed healing of the gastric mucosa.

The more you eat, the more severe the effects. At the same time, having pre-existing digestive or respiratory conditions makes you more susceptible to experiencing side effects. And while raw onions are the worst, fried or otherwise cooked onions can be just as bad for you. It is important to remember that not everyone responds the same way to a food and, while there are people who tolerate onions well, there are also those who cannot eat them because of the adverse effects they experience. With this in mind, let’s find out what are the top 11 side effects of eating onions:

Are onions bad for you

1) Irritant food. For the most part, the side effects of onions are due to the fact they are an irritant food. Essentially all the more or less pungent compounds in the vegetable, notably the organic sulfur compounds, have an irritating effect. What we know as the flavor and odor of onions is actually an innate defense system meant to repel wildlife and microorganisms (bacteria, fungi, parasites) by producing serious discomfort and even injury so that the vegetable loses its appeal. Humans are not exempt from this and will experience unpleasant digestive or other effects meant to discourage consumption of the vegetable, some more than others. Onions irritate the eyes, nose, throat, stomach, skin, even bladder and existing ulcers.

How do onions make you cry? Essentially when you slice an onion or take a bite of a bulb, the onion cells release sulfur compounds in response to this damage to the bulb. Onions first release the enzyme alliinase which goes through several transformations. One of the resulting sulfur compounds is syn-Propanethial S-oxide which is also a tear-causing agent and one of the main reasons onions make you cry. Other sulfur compounds also cause irritation to the skin, nose, throat, stomach etc.

2) Onions bad breath and bad smelling sweat. Because of their content of pungent sulfur compounds, eating onions can cause bad body odor, starting from bad breath (halitosis) to bad smelling sweat. The bad breath is caused by sulfur compounds which are absorbed into the bloodstream and released when the blood reaches the lungs via exhalation. When gastroesophageal reflux is also present, the bad breath may occur when gastric juices containing odorous onion elements rise up into the esophagus, releasing the pungent smell directly. The other type of bad odor from onions, the bad smelling sweat, occurs when sulfur compounds are broken down and released through sweat through the pores of the skin.

Because of how these odorous compounds are processed, it may actually take a few days to get rid of all the bad body odor from onions. The more you eat, the more the smell will linger, even if you shower. It could help to try to sweat out the onions smell through exercise. Garlic causes a similar bad body odor, known as garlic body smell. Read more about foods to eat and to avoid for body odor.

Onions side effects

3) GERD (gastroesophageal reflux disease). Onions are bad for acid reflux disease. Whether you eat them raw or cooked, they can work up the stomach, increase stomach acid production which, in turn, increases the pressure on the ring of muscles that keep the stomach juices in. This results in stomach juices escaping in the esophagus and causing acid reflux. At the same time, it has been proposed that onions also weaken the ring of muscles that keep stomach juices in, causing the muscles to relax and let stomach juices escape into the esophagus, resulting in acid reflux.

Another reason why onions cause stomach acidity is because of their content of fructose which stimulates fermentation, leading to stomach gas and burping which increases the chances of stomach juices also escaping into the esophagus. Raw onions tend to cause more severe GERD symptoms. Also, while eating onions causes acid reflux in those with existing GERD, it can also cause acid reflux in healthy people without a history of GERD. Read more about what foods to eat and to avoid for acid reflux.

4) Onions and gastritis. The same compounds that make onions healthy to eat cause them to be bad for gastritis. First of all, the pungent compounds in the vegetable are natural irritants and can cause stomach upset, especially when you eat too much onion. Secondly, the bulbous vegetable is thought to increase stomach acid production which can easily lead to imbalances and an irritated stomach mucosa and ultimately gastritis. While healthy people are generally not affected by an infrequent and moderate intake of onions, eating onions frequently and in relatively large amounts can both cause gastritis in healthy individuals and worsen symptoms of an existing gastritis.

5) Onions and indigestion. The foods that are easiest to digest are, for the most part, light foods with less aromatic compounds. The richer the food and the higher its aromatic profile, the more likely you are to experience gastrointestinal side effects. And believe it or not, this is also true for onions. Their potential to increase gastric juices secretion and upset the stomach, their aromatic profile, rich in pungent, organic sulfur compounds, their content of fructose which triggers gas and eructation, their irritating nature and all the ways they lead to acid reflux results indigestion with symptoms such as heartburn, nausea, gas and eructation, fullness and general stomach upset.

6) Onions and IBS. One reason why onions are bad for IBS is because of their fructans content. Fructans denominates a type of dietary fiber and includes inulin which is a soluble fiber that is fermented by bacteria in the gastrointestinal tract. On the one hand, such compounds have prebiotic benefits, helping maintain healthy gut bacteria populations and digestive health. On the other hand, the fermentation process releases air which causes abdominal fullness, bloating, burping and flatulence, all symptoms of IBS. Because they contain fructans and inulin, onions have the potential to worsen irritable bowel syndrome such as make diarrhea worse.

7) Onions gastrointestinal effects. Even without an existing gastrointestinal condition, sometimes onions are bad for the stomach. A lot of people in good digestive health experience bloating, gas and pain after eating the vegetable. However, if onions cause really bad gas, then it’s possible to have a sensitivity or intolerance to compounds in the vegetable such as the fiber inulin or fructans in general or even irritable bowel syndrome. Nursing mothers have reported that eating onions has caused their babies to have gas and colic. Lastly, raw onions are known to cause severe heartburn in individuals without a history of digestive conditions.

8) Onions and sleep. It is not uncommon for the vegetable to work up the stomach and cause such severe heartburn that it wakes you up from your sleep. It is especially harmful to eat onion at night because you will be digesting it when you should be sleeping and its various effects on the gastrointestinal tract can cause insomnia.

9) Onions headaches. The volatile, odorous constituents released when you cut onions can act as irritants not only for the eyes, but sometimes for the respiratory system as well, including nasal passages and sinuses. Inhaling the onion odor can cause sneezing and sometimes headaches. Occasionally, a headache or sneezing after eating onions or handling them can be a sign of an intolerance to certain compounds in the vegetable or allergic reaction.

10) Allergic reactions and anaphylaxis. Although rare compared to other food allergies, onion allergy is possible. Some people experience symptoms of an allergic reaction such as skin rash with redness and itching, eye irritation, inflammation of the nasal passages from smelling the onions, runny or stuffy nose, postnasal drip, lightheadedness, blurred vision, sweating, feeling of warmth, low blood pressure, nausea, vomiting, breathing difficulties, asthma and anaphylaxis. Allergy is more common to raw onions.

11) Laryngospasms and asthma. One of the main causes of laryngospasms is acid reflux and eating raw and cooked onions and especially eating onions at night, before sleep can easily cause a laryngospasm where the throat closes up for up to one minute, causing breathing difficulties and panic. Stomach acidity from eating onions can also cause an asthma episode in anyone with the condition. Some specialists recommend avoiding pungent, spicy foods and all problematic foods that cause acid reflux if you have asthma or other chronic respiratory diseases.

2 Replies to “11 Side Effects of Eating Onions”

  1. The dark green leaves of green onions are low FODMAP, but the white bulbs contain fructans. If you are in the elimination phase or know you are sensitive to fructans make sure to only use the dark green parts.

    • Thank you, Hendra. This is valuable information. In addition to onion greens or spring onions, you can use chives or green, leek tops for a low FOODMAP diet. It is recommended to only use the darker green tops and avoid the parts that are lighter colored, those that transition from green to white.

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