“Abdominal bloating is a frequent and bothersome but poorly understood clinical problem”

It’s not a subject for dinner table conversation but about 15-30 percent of the population experiences it,  it can be very painful, and it’s just beginning to get the respect it deserves in the research arena.  It”s bloating and it has nothing to do with being fat. It usually shows up as an alarmingly distended abdomen complete with gas and cramps. It can send you to bed huddled in pain. If you haven’t experienced real bloating, let’s hope you never do.

big stomachs

‘Bloating’ (in various forms :)) affects many in our society. (These bellies are simply fat – not bloated).

In somewhat fractured English, the Korean authors of this overview describe bloating as having a ‘full belly’ or “heavy and uncomfortable feeling in the abdomen.” For me, I would describe it as “looking like you’re pregnant.” I’m surprised I don’t have stretch marks after some of my bigger bloating episodes.

J Neurogastroenterol Motil. 2013 Oct;19(4):433-453. Epub 2013 Oct 7.Abdominal Bloating: Pathophysiology and Treatment. Seo AYKim NOh DH.

The causes of bloating are complicated, the underlying mechanisms are unclear, no standardized treatments exist, and few clinical trials have occurred. Sound familiar? Even the definition of bloating is a bit unclear: bloating used to refer to abdominal distension, but it’s clear that bloating and discomfort can occur without a bulging abdomen.

Bloating was not described in the medical literature until 1949 when a Mayo clinic doctor described its existence in a woman with ‘psychological problems.’  (Women experience more bloating than men).  If you experience bloating at least 3 days a month, you’re considered a ‘bloater.’

Gastrointestinal symptoms including bloating are greatly increased in people with fibromyalgia compared to controls. Over 75% of people with IBS experience bloating.  Over 50% of people who experience bloating state that they have to reduce their activities because of it, and over 40% take medications for it (or would if they could find them). Bloating can be a serious problem.


Altered Gut Flora

Several studies have found unusual populations of gut microbiota or flora or bacteria in ‘bloaters.’  Some studies suggest   that altered carbohydrate and protein metabolism due to bad gut flora causes higher levels of acids. These acids then inflame the gut lining.

Small Intestine Bacterial Overgrowth

Increased levels of gas in the small intestine has been reported to cause bloating in people with IBS, and studies indicating that antibiotics can reduce bloating and pain indirectly support the small intestine bacterial overgrowth claim. The H2 breath test has typically been used to detect increased levels of gas emanating from the small intestine, but the authors report the test has found similar H2 levels in IBS patients and controls. The lactulose breath test has not fared much better.

The authors do not believe, at this point, that small intestine bacterial overgrowth contributes to bloating. (A recent meta-analysis finding that a positive methane breath test, however, that was associated with constipation, IBS, and delayed transit (see below) in a meta-analysis suggested otherwise, however.)

Gas Accumulation in the Intestines

The vast majority of studies do not support that excessive gas induces bloating or abdominal pain. –Authors

One would think that gas accumulation would surely be a key factor in causing the belly to blow up like a balloon and cause pain, but many studies say it’s not so. There is little correlation between the amount of gas present and the degree of bloating and pain present.  Increased gas may contribute to gut distention, but not necessarily cause pain. That doesn’t mean that gas doesn’t play a role: the  distribution and movement of gas and  ‘gut motility’ (the ability of the gut to move its contents along) does appears to play more of a role than simply the amount of gas present; i.e., if you can keep it moving, lots of gas is not necessarily a problem.

Gut Motility

traffic jam

‘Delayed transit’ may be more important in bloating than gas accumulation

‘Delayed transit’ or getting the food in your intestines stuck in some sort of  gut traffic jam looks like it contributes to bloating.  Giving healthy people a drug designed to slow down the movement food through the gut produced bloating. Of course, (of course!) some studies find no connection at all between gut transit times and bloating, but studies finding that injected gas causes bloating and delayed transit in most IBS patients, but not in healthy controls, suggested delayed transit is a real issue for some. Why people with IBS have delayed transit is not clear.

Other studies suggest bloaters may not necessarily have more gas, but may eliminate it less well. (You can envision that as you will.)

Strange Abdominal Wall Activity or Abdomino-phrenic Dyssynergia”

“Abdomino-phrenic dyssynergia is one of main factors for abdominal distension and bloating”

With abdominal wall activity we get into more ME/CFS and FM-like territory; i.e., a seemingly paradoxical response.  Increased gut gas levels cause the abdominal walls of healthy people to tighten up and their diaphragms to relax, but the opposite occurs in many bloaters: gas causes their abdominal walls relax and  their diaphragm to tighten up. This strange reaction appears to contribute to bloating.

Food Intolerance and Malabsorption

Given the experience many bloaters have with gas producing foods of all types, it was strange to see ‘food intolerance and malabsorption’ end up near the end of the list.  It’s hard to imagine this section was ‘complete’. Elimination diets have certainly helped many, but they were not listed and neither was gluten avoidance. (I’ve reduced bloating by giving up gluten, dairy and eggs.)

Fiber, certain types of foods and dairy were, however, listed.  Too much fiber or too much of the wrong kind of fiber can slow down gut  motility and induce bloating. Bran, for instance, appears to increase gut transit times in healthy people, but can decrease them and cause bloating in some people with IBS. Studies indicate that lactose intolerance can cause bloating.

FODMAPS – A new hypothesis suggests that ‘highly fermentable’ (yum) but poorly digested (yuck) short-chain carbohydrate rich foods (Fermentable Oligo-Di-Monosaccharides and Polyols, aka FODMAPS) can cause GI problems and bloating.  (We will look more into FODMAPS later.)  Diets high in these types of carbohydrates have been tied to high rates of hydrogen production, distension by fermentation and GI symptoms.


Given that constipation slows (or is the result of slow) gut transit times, which is tied to bloating, it makes sense that constipation can cause bloating.

(One way to ameliorate constipation is to put your hands on the outside of your knees and then push your knees outwards against your hands when you’re going to the bathroom. This activates muscles that can help you get the poop out without the downward straining that causes hemorrhoids.)



Increased sensitivity to gut pain is often found in ‘bloaters’

It has long been recognized that people with IBS have increased pain sensitivity in the gut. If you stick a little balloon in their gut and inflate it, they will both notice it and feel pain from it long before healthy controls would notice it.  As fibromyalgia is to the muscles and joints, IBS is to the gut.  Sympathetic nervous system activation can contribute to this hypersensitization, and hypervigilance can play a role as well.

Being Female

Of course, being female contributes to bloating; every symptom associated with chronic fatigue syndrome and/or fibromyalgia as well as the disorders themselves appear to be more common in women.  It’s almost a given.




Short or long term courses of Rifaxamin may help

Various ways to alter the gut microflora are the top recommendations. Studies suggest that antibiotics can be effective at relieving bloating. The fact that antibiotics (or antibacterials) top the list of suggested treatments, of course, strongly implicates gut flora composition in bloating and gut pain.  The authors state that Rifaximin, a non-absorbable microbial agent, poses little risk of side effects and has a low risk of producing resistant flora. They first suggest it is suitable for ‘chronic administration’, but then later suggest it be considered as a ‘short-course’ therapeutic option for bloating.

When low dose Rifaximin has been ineffective, high dose (2,400 mgs) Rifaximin has been found to be effective. It also appears to be superior to other antibiotics such as neomycin, doxycycline, amoxicillin, and ciprofloxacin.


Study findings on the effectiveness of probiotics in reducing bloating are decidedly mixed with some studies showing effectiveness and at least an equal number not.  A meta-analysis of probiotic studies concluded there is moderate evidence that specific probiotics are useful in managing bloating. Several studies suggest that lactobacillus may increase bloating symptoms while bifidobacterium infantis may reduce them.


The evidence on antispasmodics is mixed as well. Most of the studies are small and some of the more effective antispasmodics are not available in the U.S.  However, a natural alternative, peppermint oil, has been effective in several studies.

Dietary Interventions

fresh veges and fruits

Some of the foods in this picture are not part of a low FODMAP diet

Noting that specific foods can trigger bloating, the authors asserted that a dietary history should be done.

Many studies have shown that highly fermentable, short-chain carbohydrates (FODMAPS) can cause bloating.  A low FODMAP diet was recently shown in one study to reduce bloating. (Eliminating gluten, eggs, and dairy has greatly helped reduce my bloating, but gluten is not mentioned in these studies.)

Reduce Your Bloating with Anti-foaming Agents and Charcoal

A recent multi-center trial found that a combination of activated charcoal and simethicone significantly reduced both bloating and feelings of ‘fullness.’ (Generic simethicone as well as the brands Phazyme, Flatulex, Mylicon, Gas-X, and Mylanta Gas are common OTC drugs in the US.)

Stimulating Fluid Secretion for Constipation and Bloating

Two new drugs, lubiprostone and linaclotide, significantly improved IBS symptoms including bloating in people with constipation.

peppermint plant

Some studies suggest peppermint oil can be effective in reducing bloating and abdominal distress


SSRIs and TCAs can be effective because they have both depression and pain reducing effects. These drugs may or may not help bloating per se, but they may make it less painful.


The authors recommendations were limited to treatments that had undergone studies,  and thus were limited to some extent. If you’ve reduced or conquered bloating please let us know how you did it.

  • Coming Up – a blog from a person with ME/CFS who conquered decades of bloating using treatments not mentioned in this overview

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