Could SIBO Be the Reason Your Reflux Won't Go Away?

Most people who have it don't know it has a name. They just know that eating feels like a gamble.

SIBO, short for Small Intestinal Bacterial Overgrowth, is one of the most overlooked drivers of chronic acid reflux and GERD. The number of people quietly managing the wrong diagnosis is genuinely staggering.

SIBO and Acid Reflux: Could Bacterial Overgrowth Be Behind Your GERD?

Your gut is home to trillions of bacteria, but location matters enormously. Most of those bacteria belong in your large intestine, at the far end of your digestive tract. Your small intestine, the long, winding section in the middle where most nutrient absorption happens, is supposed to stay relatively clear. When bacteria migrate there and take up residence in large numbers, they start doing what bacteria do: feeding. They get to your food before your body does, and as they ferment it, they produce gas. That gas is where the trouble starts.

The frustrating part is that SIBO doesn't announce itself with a unique set of symptoms. It shows up looking exactly like IBS, or acid reflux, or just a sensitive stomach, which is precisely why so many people cycle through treatments for years without ever getting to the root of it.

The SIBO-GERD Connection: When Acid Reflux Isn't About Acid

Here's the part that doesn't get enough attention. SIBO and acid reflux don't just happen to coexist in a lot of people. They're often causally linked, and in a direction that changes how you think about treatment.

When bacteria in the small intestine ferment food, they produce gas. That gas creates pressure, and enough pressure pushes stomach contents upward through the valve at the top of the stomach, producing the burning sensation we call heartburn.¹ For a meaningful subset of people with chronic reflux, the underlying problem isn't excess stomach acid at all. It's excess gas from bacterial fermentation, which is a fundamentally different problem with a fundamentally different solution, and one that acid-suppressing medication won't touch.

How common is SIBO, really?

More common than the diagnostic rates suggest. Research points to SIBO affecting roughly 15% of the general population, but that number likely undercounts the reality.⁴ Some studies have found that up to 78% of people with an IBS diagnosis actually have bacterial overgrowth as the underlying driver.¹ They've been treating symptoms. The cause has been sitting there, untouched.

What does SIBO actually feel like?

The experience of SIBO tends to follow a pattern. Bloating that builds as the day goes on, not a single incident but a slow accumulation. Cramping and discomfort after meals. Heartburn that doesn't respond the way it should to antacids. Gas that feels excessive and hard to explain. Constipation, diarrhea, or the particular misery of both. Nausea after eating. A foggy, fatigued quality to the day that has nothing to do with how much you slept. And sometimes, deficiencies in iron or B12, nutrients your small intestine should be absorbing, but isn't getting the chance to.⁴

If several of those feel familiar, a breath test is worth raising with your doctor. It's non-invasive, straightforward, and can give you a real answer.⁷

Why does SIBO happen?

SIBO is almost never random. There's usually something that sets it in motion.

The digestive system has a built-in cleaning mechanism called the migrating motor complex, a muscular wave that sweeps bacteria through the digestive tract between meals. When that wave slows down due to chronic stress, thyroid dysfunction, certain medications, or other conditions, bacteria have more time to settle in the small intestine and proliferate.⁶ 

Stomach acid is another line of defense that often gets overlooked: it kills a significant portion of the bacteria we swallow throughout the day, and when acid levels are chronically low, whether naturally or due to long-term PPI use, more bacteria survive.⁴ A past bout of food poisoning is another surprisingly common trigger. A single bad stomach bug can cause an immune response that damages the nerves governing gut movement, and researchers now believe this is one of the most common origins of SIBO that people never connect back to that one terrible week years earlier.⁸

What About Diet? The Role of Low FODMAP in SIBO and Acid Reflux

For people navigating both SIBO and acid reflux, diet is usually part of the conversation early. A low FODMAP approach limits the fermentable carbohydrates that bacteria in the small intestine feed on — less fuel means less fermentation, less gas, and less upward pressure on the valve that keeps stomach contents where they belong. It's not a cure on its own, but paired with the right treatment plan, it can take a meaningful edge off symptoms

If you're already eating low FODMAP, RefluxRaft fits right in — it's low FODMAP too, so it works with the dietary approach rather than against it.

Want to learn more?

Head over to our friends at siboawareness.org, a wonderful resource packed with everything you need to deepen your understanding of SIBO. From the latest research to practical guides, it's the perfect place to keep learning.

Siboawareness.org is dedicated to raising awareness among patients and practitioners of Small Intestinal Bacterial Overgrowth (SIBO), a commonly misdiagnosed digestive disorder.

Through education and research, we're making SIBO easier to recognize, test for, and treat, giving patients and providers the knowledge to reach the right diagnosis and the right treatment.

This post is for informational purposes only and does not constitute medical advice. Please consult a qualified healthcare provider for diagnosis and treatment.

Sources

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2. Pimentel M, Chow EJ, Lin HC. Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome. The American Journal of Gastroenterology. 2000;95(12):3503-3506. https://doi.org/10.1111/j.1572-0241.2000.03481.x

3. Quigley EMM. Small intestinal bacterial overgrowth: what it is and what it is not. Current Opinion in Gastroenterology. 2014;30(2):141-146. https://doi.org/10.1097/MOG.0000000000000040

4. Bures J, Cyrany J, Kohoutova D, et al. Small intestinal bacterial overgrowth syndrome. World Journal of Gastroenterology. 2010;16(24):2978-2990. https://doi.org/10.3748/wjg.v16.i24.2978

5. Saffouri GB, Shields-Cutler RR, Chen J, et al. Small intestinal microbial dysbiosis underlies symptoms associated with functional gastrointestinal disorders. Nature Communications. 2019;10:2012. https://doi.org/10.1038/s41467-019-09964-7

6. Siebecker A, Sandberg-Lewis S. Small Intestine Bacterial Overgrowth: Often-Ignored Cause of Irritable Bowel Syndrome. Townsend Letter. 2013. Available at: www.siboinfo.com

7. Rezaie A, Buresi M, Lembo A, et al. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders. The American Journal of Gastroenterology. 2017;112(5):775-784. https://doi.org/10.1038/ajg.2017.46

8. Pimentel M, Lembo A. Microbiome and Its Role in Irritable Bowel Syndrome. Digestive Diseases and Sciences. 2020;65:829-839. https://doi.org/10.1007/s10620-020-06109-5