How To Reduce Hydrogen Sulfide In The Gut

How to Reduce Hydrogen Sulfide in the Gut: A Comprehensive Guide

Hydrogen sulfide is a gas produced naturally in the body, particularly in the gut, where it plays a role in cellular signalling and maintaining both gut and systemic health. However, when hydrogen sulfide levels become too high, it can lead to digestive issues such as bloating, gas, and diarrhoea. High levels of hydrogen sulfide can disrupt gut function, by contributing to imbalances within the gut microbiome, leaky gut, and inflammation, thus, negatively affecting overall health.

In this article, we’ll explore what causes excess hydrogen sulfide in the gut, the symptoms to watch for, and evidence-based strategies to reduce it effectively.

What Causes Excess Hydrogen Sulfide in the Gut?

Hydrogen sulfide is produced by certain bacteria during the fermentation of sulfur containing foods and proteins. While small amounts are beneficial, overproduction can occur due to:

1. Gut Dysbiosis: Imbalance in gut bacteria, especially an overgrowth of hydrogen sulfide producing bacteria like Desulfovibrio and Bilophila wadsworthia. Hydrogensulfide is toxic to lactobacillus bacteria so you often see low levels of lactobacillus is stool testing (source)
2. SIBO (Small Intestinal Bacterial Overgrowth): When bacteria grow excessively in the small intestine, some strains produce large amounts of hydrogen sulfide.
3. High Protein/Sulfur Diet: Diets rich in protein/sulfur containing foods (like red meat, garlic, onions, eggs, and cruciferous vegetables) can fuel hydrogen sulfide production. This is likely only relevant within the context of a low fibre diet (source), and/or poor digestive function. In regards to the latter we are specifically thinking about low stomach acid which is essential for optimal digestion of protein.
4. Poor Bile Acid Metabolism: Bile acids are key regulators of the gut microbiome, playing a role in hydrogen sulfide production by specific bacteria. This process involves a complex interaction in which certain bile acids—especially those conjugated with taurine—act as a fuel source for microbes that generate hydrogen sulfide. As a result, bile acid metabolism can shape the microbial environment and may have significant effects on gut health.
5. Chronic Inflammation: Inflammatory gut conditions like ulcerative colitis can alter the gut environment, increasing hydrogen sulfide levels.
6. Fast Transit: If food is travelling through the large intestine too quickly, theoretically this may lead to symptoms of excessive hydrogen sulfide. The reason being is hydrogen sulfide is metabolised by the colonocytes – cells that make up the lining of the large intestine. If they do not have enough time to metabolise the hydrogen sulfide, then there’s only one place for the gas to go!! The result? Sulfur smelling flatulence.

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What Bacteria Product Hydrogen Sulfide?

Known bacteria that have the potential to produce hydrogen sulfide include:

Fusobacterium, Clostridium, Escherichia, Salmonella, Klebsiella, Streptococcus, Desulfovibri, and Enterobacter, are able to metabolize cysteine and create H2S. (source)

Symptoms of High Hydrogen Sulfide Levels

Excess hydrogen sulfide in the gut may lead to a variety of symptoms, including:

• Digestive issues: bloating, gas, diarrhoea, constipation, abdominal discomfort, leaky gut.
• Brain fog and fatigue.
• Sulfur smelling gas or stools.
• Bad breath (with a rotten egg odour).
• Nausea or food intolerances.
• Rashes/hives/skin conditions.

How to Test for Hydrogen Sulfide Overgrowth

1. Breath Testing: A hydrogen sulfide breath test measures the levels of gases like hydrogen, methane, and hydrogen sulfide after consuming a sugar solution. Unfortunately this is only available in the U.S.A at this point in time.
2. Stool Testing: Advanced stool tests like our Ultimate Gut Health Test can identify the presence of hydrogen sulfide producing bacteria in the gut.

Other helpful lab tests, according to Dr. Greg Nigh include:

• A complete blood count.
• MCV.
• MCH.
• Serum B12.
• Homocysteine.
• GGT.
• Iron and Ferritin.

How to Reduce Hydrogen Sulfide in the Gut

Reducing hydrogen sulfide involves a combination of dietary changes, targeted supplements, and lifestyle modifications. Here are the most effective strategies:

1. Modify Your Diet

• Reduce High Sulfur Foods: For a few years now the recommendation to follow a low sulfur diet has been common practice. Foods high in sulfur, include red meat, garlic, onions, cruciferous vegetables (broccoli, cabbage, cauliflower), eggs, and dairy. I don’t always feel this is necessary, but can provide symptom relief in the short term while you address the underlying imbalances. Ideally though, we want to keep the diet as diverse and nutrient dense as possible so I don’t see this diet as an essential step. It will depend on the individual, theirs needs and desires. (source)
• Low (at least not high) fat: The primary hydrogen sulfide (H2S)-producing bacteria in the human gut include Desulfovibrio, Bilophila wadsworthia, and Fusobacterium nucleatum. These microbes flourish in diets rich in animal protein and fats. If you’re dealing with an overgrowth of H2S-producing bacteria, it may be wise to steer clear of a ketogenic diet until your gut health is restored. Instead, a diet higher in fiber and predominantly plant-based—such as the Mediterranean diet—could be more beneficial for rebalancing your microbiome. (source)
• Low-FODMAP Diet: This diet reduces fermentable carbohydrates, which can feed hydrogen sulfide-producing bacteria. You can see above how some foods high in sulfur, are also high FODMAP foods.
• Increase Fiber: Soluble fiber from fruits, oats, and legumes helps promote healthy gut bacteria that don’t produce hydrogen sulfide. I have found prebiotics to be very helpful here (more on this below).
• Polyphenols: Include foods rich in polyphenols, like berries, green tea, coffee, and olive oil (think colour!).

“Increased fiber intake may reduce hydrogen sulfide production irrespective of protein intake, enabling the ability to meet the metabolic demands of the illness while supporting gut health.” (source)

This quote comes from a paper published in 2024 and is music to my ears. I have always believed that a lot of the research cited within the context of the microbiome is highly reductionistic and often not translatable to humans (the animal research that is).

2. Use Targeted Supplements

• Molybdenum: A trace mineral that supports sulfur metabolism, helping break down excess hydrogen sulfide.
• Probiotics: Strains like Lactobacillus plantarum and Bifidobacterium infantis may help rebalance gut bacteria and reduce H₂S production. I have had success with EveryDay Max, Saccharomyces Boulardii.
• Prebiotics: PHGG is a well tolerated prebiotic that may support microbiome diversity. It can easily be added to your morning coffee for a gut-friendly start to your day.
• Butyrate Supplements: My preferred product is Tributyrin but a more cost effective option is Sodium Butyrate. Butyrate support gut lining health and may help regulate bacterial overgrowth.
• Vitamin B12: This is the product Dr. Greg Nigh recommends as part of his protocol (watch our interview with him below). Vitamin B12 has an essential role to play within sulfur metabolism.
• Ground Flaxseed: In his book The Devil In The Garlic Dr. Nigh explains: “One approach is to inhibit the enzymes that are responsible for producing it. That’s precisely what flaxseed powder does. It inhibits those two major enzymes involved in hydrogen sulfide production, CBS and CTH, both discussed in detail in Chapter 2. The perk here is that flaxseed powder is a great source of dietary soluble fiber, providing some of the prebiotic fuel needed for healthy bacteria to produce much-needed short-chained fatty acids. I typically dose this at 1 tablespoon twice daily sprinkled on food, blended into a smoothie, mixed into (gluten-free) oatmeal, or for the brave, simply stirred into water.“
• Psyllium Husks: In one paper the researchers discussed that even fibers that ferment slowly or inefficiently showed a slight ability to suppress hydrogen sulfide, despite their limited role in bacterial fermentation. Psyllium, a highly soluble and viscous carbohydrate, exhibits gel-forming properties that may contribute to this effect. It is likely that these fibers help ‘trap’ hydrogen sulfide generated by gut bacteria by drawing in water and forming a thick gel within fecal matter. This mechanism could explain their passive role in reducing H2S levels. (source)
• Epsom salts: Epsom salts are a helpful way of getting sulfur as it bypasses the gut and the gut microbiome.

3. Address Gut Infections and Overgrowth

I have have had horrendous issues with hydrogen sulfide….horrendous! I had a gut infection and my gut was inflamed (I had elevated calprotectin). In this instance, one step is going to be addressing the infection. We have two options here, the conventional route, or a more ‘natural’ route.

• Antimicrobial Herbs: Natural antimicrobials like oregano oil, or berberine, can reduce harmful bacteria.
• Antibiotics (when necessary): In cases of severe SIBO, doctors may prescribe antibiotics like rifaximin.

4. Improve Digestion

• Betaine HCI: Optimal digestion of protein is essential when considering hydrogen sulfide production (and gut health generally).
• Digestive Enzymes: Aid in breaking down food properly, reducing fermentation that fuels H₂S production.

5. Manage Stress

Chronic stress can disrupt gut function and worsen dysbiosis. Incorporate stress-reducing practices like:

• Meditation and deep breathing exercises.
• Regular physical activity.
• Mindfulness and yoga.

Key Takeaways

• Identify the Cause: Test for SIBO, dysbiosis, or other gut imbalances to determine the root cause.
• Adjust Your Diet: Be mindful of sulfur-rich foods, support gut-friendly bacteria, and lower fermentable carbs if needed.
• Support Gut Health: Use targeted supplements like probiotics, molybdenum, and bile support to optimise digestion.
• Seek Professional Guidance: Work with a healthcare provider or functional medicine practitioner to create a personalised plan.