Unlocking ISO
The Hidden Culprit Behind Bloating & Chronic Diarrhea
Imagine this ... you've been battling digestive issues for months, maybe even years. Bloating, abdominal pain, unpredictable bouts of diarrhea – the works. You've changed your diet, popped probiotics like candy, and undergone numerous tests that all came back “normal”.
Yet here you are, still battling the bloat, the pain, the frustrating trips to the bathroom.
What if I told you that the real culprit behind your gut issues could be a stealthy saboteur in your intestines, overlooked by outdated testing methods?
Let’s shine a light on Intestinal Sulfide Overproduction (ISO), the lesser-known but equally troublesome cousin of SIBO that's potentially wreaking havoc on your gut health causing severe diarrhea, among other symptoms.
This isn't just another trendy diagnosis. ISO is a game-changer in understanding why so many are still suffering despite doing "everything right".
ISO is characterized by excess hydrogen sulfide gas produced in the intestines, primarily by sulfate-reducing bacteria. Symptoms can include severe diarrhea, bloating, abdominal pain, and even fatigue and brain fog.
To understand ISO, we first need to take a closer look at the bustling community living inside your intestines. Your gut microbiome is home to trillions of microorganisms – bacteria, fungi, viruses, and more – all working together in a delicate harmony to keep you healthy.
When the gut microbiome is in balance, your digestive system runs smoothly. But when one group of microbes starts to dominate, problems arise.
What is ISO?
In a healthy gut, microbes produce small amounts of various gases as byproducts of their metabolic processes. The three primary fermented gases are hydrogen, methane, and hydrogen sulfide.
In optimal conditions, these fermented gases remain at very low levels. However, when imbalances occur, any of these gases can increase dramatically, leading to various digestive issues such as SIBO, IMO, and ISO.
Untangling the Acronyms: SIBO, IMO, and ISO
Let's clear up some potentially confusing terminology. You may have heard of SIBO, but what about IMO and ISO and how are they different?
Here's a quick breakdown:
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SIBO (Small Intestinal Bacterial Overgrowth): This broad term refers to an excessive growth of bacteria in the small intestine. Traditionally, SIBO has been associated with the overproduction of hydrogen gas (H2).
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IMO (Intestinal Methanogen Overgrowth): Previously known as methane-dominant SIBO, IMO involves an overgrowth of methane-producing archaea (CH4) in the gut. It's often associated with constipation-predominant symptoms.
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ISO (Intestinal Sulfide Overproduction): ISO, formerly known as hydrogen sulfide-dominant SIBO, describes an overproduction of hydrogen sulfide gas (H2S) in the intestines, which causes symptoms like chronic diarrhea and bloating.
Dr. Mark Pimentel, renowned gastroenterologist and SIBO and IBS researcher, introduced the ISO terminology to distinguish it from traditional SIBO and IMO conditions. While they share some similarities, the underlying mechanisms and treatment approaches can be quite different.
By separating ISO as its own entity, the need for targeted testing, diagnosis, and treatment is better emphasized.
ISO Testing & Diagnosis - The Missing Piece of the Puzzle
One reason ISO remained under-recognized for so long was the challenge in diagnosing it. This was often due to:
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Overlapping Symptoms: ISO shares many symptoms (bloating, diarrhea, etc.) with other gut disorders, making it difficult to distinguish based on clinical presentation alone.
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Limitations of 2-Gas Breath Tests: For decades, gut health breath testing focused on measuring two primary gases: hydrogen and methane. There was no breath test available to measure excess hydrogen sulfide, so ISO could not be detected - until now.
Traditional 2-gas breath tests missed a third of the picture. Without measuring for hydrogen sulfide, it was like trying to solve a puzzle with a crucial piece missing – close, but never fully seeing the complete picture.
The Breakthrough: 3-Gas Breath Testing
Recent advancements have led to the development of an innovative 3-gas breath test that measures all three fermented gases in the gut: hydrogen, methane, and hydrogen sulfide. This breath test is non-invasive, can be ordered online, and easily conducted at home.
Beyond diagnosis, another benefit of the 3-gas breath test is its prognostic value. By measuring hydrogen sulfide levels, this test can predict the severity of diarrhea a patient might experience.
The amount of hydrogen sulfide produced correlates strongly with the intensity of diarrheal symptoms. This allows healthcare providers to better tailor treatment plans and give patients a clearer picture of what to expect.
Treatment Approaches for ISO
In general, managing and treating ISO can involve a combination of targeted medications and dietary adjustments, often tailored to the individual patient. The primary goal of treatment is to reduce the overgrowth of hydrogen sulfide-producing bacteria and manage the associated symptoms.
Targeted Medications
Because the ability to test and measure hydrogen sulfide is a recent discovery, the best course of action is still being investigated. However, rifaximin and bismuth are often the first line of treatment and show promising results:
Rifaximin, a broad-spectrum antibiotic, is commonly used due to its effectiveness and minimal absorption in the bloodstream, which helps reduce bacterial overgrowth.
Bismuth subsalicylate, the main ingredient in Pepto-Bismol, has been found to reduce hydrogen sulfide producers in the gut and improve symptoms.
Dietary Recommendations
Diet plays a crucial role in managing ISO, but knowing when and how to implement one that supplies vital nutrients can sometimes be confusing.
Low-sulfur diet
Sulfur fuels hydrogen sulfide-producing bacteria, so a low-sulfur diet, which limits foods high in sulfur, can help decrease the hydrogen sulfide levels in your gut. Foods to consider limiting include:
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garlic
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onions
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cruciferous vegetables (broccoli, cauliflower, cabbage, kale, sprouts)
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red meat
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eggs
Low-FODMAP diet
A low-FODMAP diet reduces foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, all types of carbohydrates that can ferment in the gut easily. This diet can help by limiting the food supply for bacteria that produce hydrogen sulfide. Foods to avoid may include:
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wheat
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garlic
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onions
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beans and lentils
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apples
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pears
Low-fermentation diet
Designed with SIBO patients in mind, a low-fermentation diet goes a step further by focusing on foods less likely to ferment in the gut, thereby reducing the production of gases, including hydrogen sulfide.
This diet typically emphasizes easily digestible proteins, certain low-carb vegetables, and healthy fats, while avoiding foods that tend to ferment, such as high-fiber grains, legumes, and high-sulfur vegetables.
The goal is to minimize fermentation and reduce the bacterial load that contributes to hydrogen sulfide production. Foods you may want to avoid include:
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non-absorbable sugars, including sucralose, sorbitol, lactitol, xylitol, and mannitol
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food additives, such as inulin
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cruciferous vegetables, cabbage, sauerkraut, brussels sprouts, and broccoli
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beans, chickpeas, and lentils
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milk and other dairy products
In addition to food choices, the low-fermentation diet involves timing when you eat your meals. This includes avoiding eating and snacking for four to five hours between meals allowing the digestive system time to clear bacteria and reduce overall fermentation.
If you have questions about which diet may be most beneficial to you, consider consulting with a licensed dietician or nutritionist or talking to your doctor.
The Takeaway
Living with unexplained digestive issues can be a lonely and frustrating journey. The constant discomfort and social anxiety can take a toll on your daily life. ISO represents a significant breakthrough that may provide the missing piece of the puzzle for those who have struggled despite negative tests for traditional SIBO.
Imagine finally having an explanation for your symptoms. With proper diagnosis through comprehensive 3-gas breath testing, you can move from confusion to understanding and action.
As research evolves, it's crucial for both healthcare providers and patients to stay informed about ISO. If you've been battling with unexplained gut issues, consider discussing ISO and 3-gas breath testing with your healthcare provider. This new understanding of ISO could be the path to relief and feeling like yourself again.
ISO FAQs
What causes ISO?
Can excess hydrogen sulfide be detected by odor in breath or stool?
What is the relationship between ISO and IBS?
How is ISO different from other types of SIBO?
Can I have SIBO, IMO, and/or ISO at the same time?
Can I have ISO and not have SIBO or IMO?
What is the difference between a 2-gas and 3-gas breath test?
Can ISO cause other health problems?
Can I still eat sulfur-rich foods if I have ISO?
Are there any natural treatments for ISO?
References:
Hafen BB, Burns B. Physiology, Smooth Muscle. [Updated 2023 Aug 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526125/
Pimentel M, Rezaie A. The Microbiome Connection: Your Guide to IBS, SIBO, and Low-Fermentation Eating. Agate Surrey; 2022.
Rana SV, Malik A. Hydrogen breath tests in gastrointestinal diseases. Indian J Clin Biochem. 2014 Oct;29(4):398-405. doi: 10.1007/s12291-014-0426-4
Skrzydło-Radomańska B, Cukrowska B. How to Recognize and Treat Small Intestinal Bacterial Overgrowth? J Clin Med. 2022 Oct 12;11(20):6017. doi: 10.3390/jcm11206017
Villanueva-Millan MJ, Leite G, Morales W, Sanchez M, et al. Hydrogen Sulfide Producers Drive a Diarrhea-Like Phenotype and a Methane Producer Drives a Constipation-Like Phenotype in Animal Models. Dig Dis Sci. 2024 Feb;69(2):426-436. doi: 10.1007/s10620-023-08197-5
Villanueva-Millan MJ, Leite G, Wang J, et al. Methanogens and Hydrogen Sulfide Producing Bacteria Guide Distinct Gut Microbe Profiles and Irritable Bowel Syndrome Subtypes. Am J Gastroenterol. 2022 Dec 1;117(12):2055-2066. doi: 10.14309/ajg.0000000000001997