What is Irritable Bowel Syndrome (IBS)?

What Is Irritable Bowel Syndrome (IBS)?

IBS is one of those diagnoses that patients mention almost apologetically. Most people don't walk into my office saying "I have IBS." They tell me about gas, bloating, unpredictable bowel movements, stomach pain that comes and goes.

They've learned to plan their lives around bathroom access. They know which foods will wreck them for days. They've been told it's stress, or anxiety, or just something they'll have to live with.

Here's the reality: about 20% of the population suffers from some form of IBS. That's one in five people walking around with a gut that's actively rebelling against them.

But IBS isn't a disease. It's a symptom cluster pointing to underlying dysfunction that conventional medicine rarely addresses. When your doctor diagnoses you with IBS, what they're really saying is "your digestive system isn't working right, and we don't know why."

The good news? We do know why. And more importantly, we know how to fix it.

The Official Diagnosis (And Why It's Inadequate)

IBS is diagnosed when you've had abdominal pain or discomfort at least three times a month for the last three months, without other disease or injury that could explain it. The pain typically changes with stool frequency or consistency, or gets better after a bowel movement.

There are four official subtypes based on stool patterns:

IBS-C (Constipation-Predominant): Hard or lumpy stools at least 25% of the time, loose or watery stools less than 25% of the time. Your gut moves too slowly, water gets reabsorbed, everything backs up.

IBS-D (Diarrhea-Predominant): Loose or watery stools at least 25% of the time, hard or lumpy stools less than 25% of the time. Your gut moves too quickly, water doesn't get reabsorbed, you're running to the bathroom constantly.

IBS-M (Mixed): Hard or lumpy stools at least 25% of the time AND loose or watery stools at least 25% of the time. This is the most common type I see in practice. Your gut can't decide what it's doing from one day to the next. Constipation for three days, then explosive diarrhea. Rinse and repeat.

IBS-U (Unsubtyped): Neither constipation nor diarrhea meet the 25% threshold. Your symptoms are there, they're real, they're disrupting your life, but they don't fit neatly into the other categories.

These classifications are useful for tracking symptoms. They're terrible at identifying causes.

What Actually Causes IBS

Conventional medicine treats IBS as a mystery. It's not. The causes are well-documented in research, just not well-implemented in standard gastroenterology practice.

IBS is driven by some combination of: bacterial overgrowth in the small intestine (SIBO), increased intestinal permeability (leaky gut), gut-brain axis dysfunction, microbiome imbalance, food sensitivities, low stomach acid, and chronic stress.

Let's break down each one.

SIBO: The Most Common Culprit

Small Intestinal Bacterial Overgrowth. Your small intestine is supposed to have relatively few bacteria compared to your large intestine. When bacteria migrate upward or overgrow in the small intestine, they ferment food that hasn't been fully digested yet.

This fermentation produces gas. Lots of gas. Hydrogen gas, methane gas, sometimes hydrogen sulfide gas. These gases create the bloating, distension, pain, and altered motility that define IBS.

Hydrogen-dominant SIBO tends to cause diarrhea (IBS-D). The gas speeds up intestinal transit, pushing everything through too quickly.

Methane-dominant SIBO tends to cause constipation (IBS-C). Methane slows intestinal motility, everything moves like sludge.

Mixed SIBO creates mixed symptoms (IBS-M). You get both gases, your gut oscillates between too fast and too slow, and your life becomes unpredictable.

Studies show that 60-80% of IBS patients test positive for SIBO. This isn't a coincidence. For most people with IBS, SIBO is the underlying mechanism.

Leaky Gut and IBS

Your intestinal lining is one cell thick, held together by tight junction proteins. When these junctions loosen (from stress, inflammation, bacterial overgrowth, or certain foods), larger molecules slip through into your bloodstream.

This intestinal hyperpermeability triggers immune responses, creates systemic inflammation, and contributes to food sensitivities. The mechanism of how leaky gut develops involves zonulin, stress, inflammatory foods, and bacterial imbalance.

When your gut is leaky, you're more likely to react to foods. These reactions create inflammation in the gut lining, which worsens motility issues and contributes to IBS symptoms.

The relationship is bidirectional: SIBO can cause leaky gut (bacterial endotoxins damage tight junctions), and leaky gut can worsen SIBO (immune dysfunction allows bacterial overgrowth). They feed each other in a vicious cycle.

The Gut-Brain Connection

Your gut has more neurons than your spinal cord. The enteric nervous system (your "second brain") communicates constantly with your actual brain via the vagus nerve.

When you're stressed, anxious, or overwhelmed, your brain sends signals that alter gut motility, increase gut permeability, change digestive enzyme secretion, and shift the bacterial balance in your microbiome.

This is why stress makes IBS worse. It's not psychosomatic. It's neurophysiological.

Your gut also produces about 90% of your body's serotonin. When gut function is disrupted, serotonin production changes. This affects both gut motility (serotonin regulates intestinal contractions) and mood (serotonin regulates emotional state).

This is why people with IBS often also struggle with anxiety or depression. Same root dysfunction, different manifestations.

The Microbiome Factor

Your large intestine contains trillions of bacteria. When the balance shifts toward pathogenic species or away from beneficial ones (dysbiosis), you lose the protective functions these bacteria provide.

Beneficial bacteria produce short-chain fatty acids (like butyrate) that fuel your intestinal cells, regulate inflammation, and maintain gut barrier integrity. They also keep pathogenic species in check through competitive inhibition.

When dysbiosis develops (from antibiotics, poor diet, chronic stress, or infections), the protective species decline. Pathogenic species proliferate. Inflammation increases. The gut barrier weakens. Motility becomes erratic.

All classic IBS symptoms.

Food Sensitivities and IBS

Many people with IBS react to specific foods. Not because those foods are inherently bad, but because their gut barrier is compromised and their immune system is hypervigilant.

Common trigger foods include: gluten (triggers zonulin, increases permeability), dairy (lactose fermentation, casein sensitivity), FODMAPs (fermentable carbohydrates that feed bacterial overgrowth), processed seed oils (inflammatory), excess sugar (feeds pathogenic bacteria).

The low-FODMAP diet can help manage symptoms by reducing bacterial fermentation. But it's a management strategy, not a cure. Understanding which foods trigger IBS is important, but understanding why you're reacting is more important.

If you don't address the underlying SIBO, leaky gut, and dysbiosis, you'll keep reacting to more and more foods as time goes on.

Low Stomach Acid: The Upstream Problem

Your stomach is supposed to be extremely acidic (pH 1.5-3.5). This acid kills pathogenic bacteria and parasites before they reach your intestines, activates digestive enzymes, and breaks down protein.

When stomach acid production is inadequate (from chronic stress, aging, PPI use, or H. pylori infection), bacteria survive passage through the stomach and colonize your small intestine.

This is how SIBO develops.

Low stomach acid also means incomplete protein digestion, which creates larger peptides that trigger immune responses when they cross a leaky gut barrier.

Fixing stomach acid production is often the first step in resolving IBS.

The Ileocecal Valve Connection

The ileocecal valve sits between your small intestine and large intestine. It's supposed to be a one-way gate, allowing digested material (chyme) to pass from small intestine to large intestine while preventing bacteria from migrating backward.

When this valve becomes dysfunctional (from inflammation, food sensitivities, or stress), it can stick open or closed.

Stuck open: bacteria from the large intestine migrate into the small intestine (hello SIBO), and you get diarrhea because material moves through too quickly.

Stuck closed: chyme backs up in the small intestine, you get constipation, bloating, and pain.

Ileocecal valve dysfunction is both a cause and effect of IBS. Fixing it requires addressing the inflammation and dysfunction upstream.

Dehydration and Fiber

Basic but critical: if you don't drink enough water, your large intestine pulls every drop of moisture from your stool. Hard, lumpy, constipated bowel movements result.

The guideline is at least two-thirds of your body weight in ounces of water daily. Water quality matters as much as quantity. Fluoride, chlorine, and chloramines in tap water can disrupt gut bacteria.

Fiber is equally important, but not from grains. Vegetable fiber (from leafy greens, cruciferous vegetables, root vegetables) provides bulk without the inflammatory lectins and gluten found in grain-based fiber.

Grain-based fiber (especially from wheat, corn, and processed cereals) often makes IBS worse by triggering inflammation and feeding bacterial overgrowth.

The Stress-IBS Cycle

Chronic stress depletes cortisol production. Without adequate cortisol, you lose the ability to control inflammation throughout your body, including in your gut.

This gut inflammation damages the intestinal lining, loosens tight junctions, and alters bacterial balance. It also affects motility through direct nervous system signaling.

Adrenal fatigue and IBS often occur together because they're mechanistically linked. The same cortisol depletion that creates fatigue, brain fog, and blood sugar instability also creates gut dysfunction.

You might be more stressed than you realize, and that stress is wreaking havoc on your digestive system even if you don't feel anxious.

Why Your IBS Keeps Getting Worse

IBS creates a self-reinforcing cycle:

Stress or infection or antibiotic use disrupts your gut bacteria → SIBO develops → Bacterial fermentation creates gas and inflammation → Inflammation damages your gut lining → Leaky gut develops → Food sensitivities emerge → You react to more foods → More inflammation → Worse bacterial imbalance → More severe SIBO → Worsening symptoms.

At the same time: stress affects gut motility and permeability → symptoms worsen → you stress about symptoms → more stress → worse gut function.

This is why IBS rarely gets better on its own. The underlying mechanisms keep reinforcing each other unless you intervene systematically.

Beyond Symptom Management

Most conventional IBS treatment focuses on symptom management: antispasmodics for cramping, fiber supplements for constipation, anti-diarrheal medications for loose stools, antidepressants for the gut-brain connection.

These can help you function day-to-day. They don't fix anything.

Addressing IBS at the root requires: testing for and treating SIBO (breath testing, antimicrobial protocols), healing leaky gut (remove inflammatory triggers, support tight junction repair), rebalancing the microbiome (targeted probiotics, fermented foods, dietary diversity), restoring stomach acid production (HCl supplementation, addressing stress), managing stress and supporting adrenal function (sleep, boundaries, adaptogenic support), identifying and temporarily removing trigger foods.

This takes time. There's no quick fix. But unlike symptom management, it actually resolves the problem.

The Food Connection

I mentioned this earlier but it's worth emphasizing: the foods that trigger your IBS are triggering it because of underlying dysfunction, not because you're broken or those foods are inherently toxic.

Someone without SIBO can eat garlic without bloating for three days. Someone without leaky gut can eat dairy without inflammation. Someone with adequate cortisol can eat a wider variety of foods without immune reactions.

The goal isn't to restrict your diet forever. It's to fix the underlying issues so your gut can handle normal foods again.

Common Symptoms Beyond The Gut

IBS symptoms extend beyond digestive issues because gut dysfunction affects your entire body:

Digestive: Gas, bloating, abdominal pain, cramping, irregular bowel movements (constipation, diarrhea, or alternating), nausea, heartburn

Neurological: Brain fog, difficulty concentrating, anxiety, depression, mood swings, headaches

Energy: Chronic fatigue, post-meal energy crashes, feeling wired but tired

Immune: Frequent infections, food sensitivities, seasonal allergies, autoimmune conditions

Skin: Acne, eczema, rosacea, unexplained rashes

Systemic: Joint pain, muscle aches, hormonal imbalances

When patients tell me they have IBS plus anxiety plus fatigue plus food sensitivities plus skin issues, I'm not surprised. It's all connected through gut dysfunction.

Testing and Assessment

Proper IBS assessment goes beyond symptom questionnaires:

SIBO Breath Testing: Measures hydrogen and methane production after consuming a sugar solution. Identifies bacterial overgrowth and which gas type dominates (which determines whether you get constipation or diarrhea).

Comprehensive Stool Analysis: Assesses bacterial balance, digestive enzyme function, inflammation markers, and presence of parasites or pathogenic bacteria.

Food Sensitivity Testing: IgG and IgA panels identify which foods your immune system is reacting to. Helps create targeted elimination protocols.

Applied Kinesiology Examination: Can identify digestive enzyme deficiencies, HCl production issues, ileocecal valve dysfunction, and food sensitivities through muscle testing.

Standard colonoscopy and endoscopy are useful for ruling out serious pathology (IBD, celiac disease, cancer), but they don't identify the functional issues driving IBS.

Moving Forward

If you've been diagnosed with IBS and told to just manage symptoms, you deserve better.

IBS isn't a life sentence. It's a signal that something in your gut ecosystem needs attention. Usually multiple somethings: bacterial balance, gut barrier integrity, stomach acid production, stress management, food sensitivities.

The conventional approach of throwing medications at symptoms while ignoring mechanisms is lazy medicine.

Your gut can heal. Your bacterial balance can be restored. Your food sensitivities can resolve. Your symptoms can disappear.

It requires understanding what's actually broken and fixing it systematically. Not just learning to live with it.

For comprehensive nutrition strategies that support gut healing and reduce IBS symptoms, visit the Fuel Your Body pillar page.

For stress management and adrenal support protocols that improve gut function, visit the Regulate Your System pillar page.

Ready to optimize your health and performance? Dr. JJ Gregor uses Applied Kinesiology and functional health approaches to identify and treat the root causes of IBS at his Frisco, Texas practice. Schedule a consultation to discover how SIBO testing, gut healing protocols, and personalized nutrition strategies can eliminate your digestive symptoms for good.