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Onions and Diarrhea – Prepare The Toilet!

Is there a relationship between onions and diarrhea? Are onions the cause of the ridiculously frequent bathroom visits you have been or maybe someone you know has been experiencing?

Onions have a very rich history in the diets of us humans. In fact, it is believed that our human species consumed onions long before writing was even invented.

And it's no wonder why our ancient ancestors loved them so much. They have become a staple ingredient in many dishes all over the world. Dressings, sauces, dry rubs, you name it… Onions are used in a wide range of foods because they have such a unique flavor that arouses the taste buds.

But.. All that delicious flavor that they add to so many different foods isn't worth it if you are going to be suffering from severe gastrointestinal distress, which often results in the eruption of diarrhea.

You Have Diarrhea If...

  • Your stool is loose and watery
  • You spend half your day running to the toilet and the other half trying not to poop your pants
  • Watery stool is accompanied by stomach cramps, bloating, etc.

Normally having diarrhea isn't too much of a concern. Everyone gets it at one point or another and it usually goes away on its own within a relatively short period of time.

However, if it lasts too long it can be serious. Diarrhea leads to nutrient deficiency as well as dehydration and this can cause a number of problems.

So if onions are to blame, and they have been causing diarrhea for you or someone you care about, then it might be best to discontinue consumption and find an alternative. If you aren't too sure if onions are the cause, you may want to try an elimination diet to narrow in on the culprit.

*If onions are causing you diarrhea then garlic is also very likely to do the same. Both are very similar and both belong to the Allium genus.

The Reason Onions Can Cause Diarrhea

Onions have what is called fructan, which is found in all sorts of foods, such as grains, fruits, vegetables and more. This is a type of carbohydrate that isn't going to be a problem to too many people, but it can cause gastrointestinal distress for some.

Having an intolerance to fructans isn't all that uncommon. In fact, many people who believe themselves to be gluten intolerant are actually probably fructan intolerant.

Fructans are malabsorbed by the small intestine and this then leads to fermentation of the fructans by gut bacteria which can cause bloating, excessive gas and diarrhea, or at least this is what researchers believe. There isn't exactly a definitive agreed upon answer as to how it all works.

The reason for these problems is because humans don't have enzymes to digest fructan. 

What About Insoluble Fiber?

There is some talk online about the insoluble fiber being the cause of diarrhea here, but this seems to be unlikely.

You see, you have insoluble fiber and soluble fiber. Having too much insoluble fiber is a common cause of diarrhea because it attracts water to the colon, which can lead to looser and more watery stools. Soluble fiber on the other hand can actually help. It can absorb water and turns into a gel-like substance, which can help prevent diarrhea.

Onions don't have all that much fiber to begin with. According to Healthfully.com, a half cup of cooked onions contains about 1.5 g of fiber total, and 1.2 g of that is soluble. 

Don't Worry, You Probably Are NOT Allergic

Some people worry that there diarrhea after eating onions comes from an allergy. However, if you are still eating onions and think you are allergic, you probably are not.

Being allergic is much more severe than being simply intolerant to some of the contents of onions. In fact, just touching an onion or taking the smallest bit of food with onion in it could trigger a severe reaction.

An allergic reaction is when your immune system goes overboard and perceives a threat that is not really a threat. Your body is basically overreacting to nothing, but the symptoms can be very serious and can potentially lead to anaphylaxis.

Diarrhea is one of the least of your concerns if you have an allergy.

Who Is Most Likely to Be Affected

Those who suffer from irritable bowel syndrome, IBS, seem to be particularly susceptible to gastrointestinal distress after eating onions.

IBS is a disorder that affects the large intestine. People with this disorder are very sensitive to the foods they consume and experience cramping, stomach pain, bloating, gas, diarrhea and constipation, much easier than the rest of us.

Fructans are oligosaccharides, which is the "O" in FODMAP.

Why does this matter? Because FODMAP is a doctor recommended diet for IBS sufferers that tells them what to avoid.

If you have IBS you want a low FODMAP diet, meaning low in oligosaccharides, meaning low in onion.

Raw Onions Reap More Havoc

If you are eating raw onions then you may want to stop doing this. Doing so seems to have a much greater effect than eating cooked onions.

This might be due to the cooking process helping make fructans more digestible, but that is just a guess. The bottom line is that eating cooked onions goes much easier on the gastrointestinal system.

Onion Alternatives for Those Suffering from Volcanic Diarrhea

Other alternatives to onions that you could give a try include things like shallots, leeks, and chives.

These are also members of the Allium genus. They are similar but not quite as caustic as onions or garlic.

Some people may be able to handle these alternatives without problem, while others may be too sensitive for these as well. It all depends on the person.

Most people aren't going to have any problem eating onions, but you aren't most people. And the last thing you want is to suffer from diarrhea continuously which will negatively impact your health in just about every way possible.

So if onions need to be taken out of your diet, so be it. Hopefully your body can handle some of the alternatives.

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Starting his writing career in 2015, Kyle is a leading contributor here at GutAdvisor, and for good reason. Having a passion for health and the awareness that proper digestion plays a key role one's overall well-being, he regularly keeps the community informed with valuable information regarding gut health.

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  1. My Dad is 93 and in the last year has had nonstop problems with diarrhea. He also was born with one kidney and now has kidney disease so I’m searching for a diet that can be a positive for both problems. Incidentally, trying Imodium and probiotics have little if any noticeable effect. We have had the most positive results with Metamucil twice a day, morning and evening. However it is not consistent results. Hit and miss so to speak.

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