Outpatiented · Case Knowledge
You are bloated after almost every meal. Sometimes you are bloated without eating at all. The doctor ran a colonoscopy, maybe a food allergy panel. Everything was normal. You got a diagnosis of IBS and a low-FODMAP handout. You are still bloated. This is because IBS is not a cause. It is a label for a pattern that has not been traced to its source.
What IBS Actually Is
Irritable bowel syndrome is defined by a set of symptoms: abdominal pain, bloating, altered bowel habits (diarrhea, constipation, or both). To be diagnosed, other identifiable causes have to be ruled out. This is where the problem begins.
The conditions that need to be ruled out for an IBS diagnosis are a short list. Inflammatory bowel disease (Crohn's, ulcerative colitis), celiac disease, colorectal cancer. Those are the exclusions. If you do not have those, you have IBS. SIBO is not on the standard exclusion list. Gut dysbiosis is not. Low stomach acid is not. Candida overgrowth is not. Food sensitivities beyond celiac are not.
IBS is a diagnosis that says the tests we ran do not show the conditions we looked for. It does not say there is no cause. It says we did not find one. Those are different things, and most people with IBS have a cause that was never looked for.
A diagnosis that describes your symptoms
is not the same as a diagnosis that explains them.
What Is Actually Causing It
Bloating is produced when gas accumulates in the digestive tract faster than it can be absorbed or expelled. Gas is produced primarily by bacteria fermenting undigested food. The question is why the food is not being digested properly, and where the fermentation is happening. Those answers point to specific, addressable causes.
The small intestine is supposed to have relatively few bacteria. The colon is where the majority of the gut microbiome lives. In SIBO, bacteria migrate up into the small intestine, where they ferment carbohydrates that are supposed to be absorbed before reaching the colon. The result is gas, bloating, and distension that begins within 30 to 90 minutes of eating, particularly after starchy or sweet foods. SIBO is diagnosed with a hydrogen and methane breath test. It is not part of a standard GI workup. It is not detectable on colonoscopy. It is one of the most common causes of chronic bloating that carries an IBS label.
Stomach acid serves two critical functions: it breaks down protein and it kills bacteria and yeast before they reach the small intestine. When stomach acid is insufficient (hypochlorhydria), protein digestion is impaired and the microbial gatekeeping function fails. Undigested protein reaches the small intestine, where bacteria ferment it. Bacteria and yeast that would have been killed by adequate stomach acid survive and populate further downstream. The result is gas, bloating, reflux (paradoxically, low acid often produces the same symptoms as high acid), and downstream dysbiosis. Long-term PPI (proton pump inhibitor) use is one of the most common causes of induced hypochlorhydria and is a frequently overlooked contributor to chronic bloating in people who were put on PPIs for reflux.
The gut microbiome is a complex ecosystem of bacteria, fungi, and archaea. When the balance shifts, certain species that produce more gas from fermentation can dominate. Dysbiosis can follow antibiotic use, a period of poor nutrition, illness, or chronic stress (which affects gut motility and microbial composition through the gut-brain axis). Standard GI workups do not assess microbiome composition. Comprehensive stool testing can identify dysbiosis patterns, but it is not a standard offering in conventional gastroenterology.
Food allergies involve IgE-mediated immune responses and are detectable on standard allergy panels. Food sensitivities involve different immune pathways (IgG, IgA, or non-immune mechanisms) and do not show up on standard allergy tests. Gluten sensitivity without celiac disease is the most discussed example, but sensitivities to dairy proteins, eggs, corn, soy, and other foods are common triggers for bloating that a negative allergy panel does not rule out. An elimination and reintroduction protocol is more informative than any blood test for identifying food sensitivities, and it is almost never recommended in standard GI care.
Candida albicans is a normal resident of the gut at low levels. Following antibiotic use, high-sugar dietary patterns, or immunosuppression, it can proliferate beyond normal levels. Candida ferments sugars and produces gas, acetaldehyde (which contributes to brain fog), and inflammatory compounds. It is not tested for in standard GI workups. Comprehensive stool testing can identify candida overgrowth. The clinical picture often includes bloating that is particularly triggered by sugar and refined carbohydrates, along with fatigue, brain fog, and a history of recurrent yeast infections or antibiotic use.
The thyroid hormone governs metabolic rate throughout the body, including gut motility. Suboptimal thyroid function slows the movement of food through the GI tract. When transit time is prolonged, food sits longer in areas where fermentation can occur, producing more gas and bloating. This is why constipation is a feature of hypothyroidism and why addressing suboptimal thyroid function can significantly improve GI symptoms even when no GI diagnosis has been made. Thyroid function is rarely considered in a GI workup focused on bloating.
Proton pump inhibitors (omeprazole, pantoprazole, esomeprazole) are prescribed for GERD, ulcers, and sometimes for unexplained GI symptoms. They work by blocking stomach acid production.
Long-term PPI use creates hypochlorhydria. With insufficient stomach acid, protein digestion is impaired, bacterial and yeast gatekeeping fails, magnesium absorption is impaired, B12 absorption decreases, and the conditions for SIBO are created or worsened. Studies consistently show higher rates of SIBO in PPI users.
A person who was put on a PPI for reflux symptoms, continued it long-term, and now has chronic bloating may be experiencing the consequence of the treatment, not a separate condition. This is rarely discussed at the prescribing visit or the follow-up.
What to Do
The low-FODMAP diet reduces fermentable carbohydrate load and often reduces symptoms. It is a management strategy, not a treatment. It does not identify or address what is causing the fermentation problem. Used alone, it requires permanent dietary restriction to maintain symptom relief because the underlying cause is still present.
The more useful path is identifying which of the root causes is driving the pattern.
Questions People Actually Ask
Why am I so bloated all the time?
Chronic bloating is produced by excessive gas in the digestive tract. Gas is produced when bacteria ferment food that was not fully digested or absorbed before it reached them. The question is where that fermentation is happening and why digestion is incomplete.
The most common causes of chronic bloating are SIBO (bacteria in the small intestine fermenting carbohydrates early), low stomach acid (allowing improper protein digestion and microbial overgrowth), gut dysbiosis (imbalanced microbiome with high-gas-producing species), food sensitivities that standard tests miss, candida overgrowth, and slow gut motility from suboptimal thyroid function.
If you have been told you have IBS, that label describes your symptoms without identifying which of these causes is driving them.
What is SIBO and how do I know if I have it?
SIBO is small intestinal bacterial overgrowth. Bacteria that belong in the colon migrate into or proliferate in the small intestine, where they ferment carbohydrates that should be absorbed first. The result is gas and bloating that begins relatively quickly after eating, particularly after starchy or sweet foods.
SIBO is diagnosed with a lactulose or glucose hydrogen and methane breath test. You drink a sugar solution and breathe into collection tubes at regular intervals. Elevated hydrogen or methane at specific time points indicates bacterial fermentation in the small intestine. This test is not included in standard GI workups and requires a specific request. It is available through gastroenterologists and some primary care or functional medicine providers.
Can low stomach acid cause bloating?
Yes, and this is one of the most counterintuitive causes of digestive symptoms because low stomach acid and high stomach acid can produce nearly identical symptoms including bloating, reflux, and discomfort.
Adequate stomach acid is required to fully break down protein and to kill bacteria and yeast before they reach the small intestine. When acid is insufficient, protein passes partially undigested into the small intestine, bacteria that should have been killed survive and populate further into the gut, and the conditions for SIBO are created or maintained.
Long-term PPI use suppresses stomach acid and is a documented contributor to SIBO in the research literature. If bloating began or worsened after starting a PPI, this connection is worth investigating.
Is it possible I have a food sensitivity that is not showing on tests?
Yes. Standard allergy panels test for IgE-mediated reactions, which are true allergies. Food sensitivities typically involve different immune mechanisms (IgG, IgA) or non-immune mechanisms (enzyme deficiencies, microbiome interactions). These do not show up on standard allergy panels.
Gluten sensitivity without celiac disease is the most documented example, but sensitivities to dairy proteins, eggs, corn, soy, and other common foods are real and can drive bloating, fatigue, and inflammation. A negative allergy panel does not rule them out.
The most accurate way to identify food sensitivities is an elimination protocol: removing the most common triggers for three to four weeks, then reintroducing them one at a time while tracking symptoms. This requires commitment but produces information no blood test can provide.
Does the low-FODMAP diet cure bloating?
The low-FODMAP diet reduces fermentable carbohydrate load, which reduces the fuel available for fermentation. For many people it significantly reduces symptoms. It is not a cure because it does not address the reason the fermentation is happening.
If you have SIBO, dysbiosis, or low stomach acid, removing FODMAPs reduces symptoms while the underlying issue remains. Returning to a normal diet typically returns the symptoms. The low-FODMAP diet is most useful as a short-term symptom-reduction strategy while identifying and treating the root cause, not as a permanent way of eating.
The MAP Tool maps your symptom pattern, your triggers, and your history to root cause. Not a low-FODMAP handout. A thread that goes somewhere.
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