SIBO Treatment: Why Treating the Bacteria Is Only the Beginning

The Modern Approach to SIBO Treatment by phenotype: Hydrogen, Methane (IMO) & Hydrogen Sulfide (ISO)

The way we think about SIBO has changed

For many years, SIBO (Small Intestinal Bacterial Overgrowth) was treated as one condition with one treatment. Research now recognises three distinct microbial conditions that produce different gases, different symptoms and, importantly, require different treatment approaches.

These include:

Condition	Main Gas	Typical Symptoms*	Main Species*
SIBO	Hydrogen	Bloating, pain, diarrhoea, rapid fermentation	Hydrogen producers: e.g. E.coli, Klebsiella spp. Ruminococcaceae
IMO (Intestinal Methanogen Overgrowth)	Methane	Constipation, slow gut transit	Methanogens: e.g. methanobrevibacter spp.
ISO (Intestinal Sulfide Overproduction)	Hydrogen sulfide	Diarrhoea, urgency, inflammation, rotten egg smelling farts, fructose malabsorption	Sulfate-reducing bacteria: Desulfovibrio spp.

*This is in no way an exhaustive list and many of my patients have different or a combination of symptoms and species found on Comprehensive Microbiome testing.

One of the most important advances in the literature is that methane is not actually produced by bacteria, but by archaea, meaning IMO is biologically distinct from traditional SIBO. Likewise, hydrogen sulfide overproduction appears to have different microbes, different mechanisms and different treatment considerations from both hydrogen SIBO and IMO. This is why I prefer testing (gas breath testing and comprehensive microbiome mapping), as it allows treatment to be tailored to the dominant microbial pattern rather than applying a generic protocol (which actually just don't work in the long-term).

Why does SIBO happen?

The bacterial overgrowth itself is rarely the original problem. In many people, SIBO develops after something disrupts the normal protective mechanisms of the small intestine, such as:

• food poisoning or gastroenteritis

• antibiotics

• chronic stress

• impaired migrating motor complex (MMC)

• constipation

• abdominal surgery

• reduced stomach acid

• medications such as PPIs

• connective tissue disorders affecting gut motility

• hypothyroidism

• coeliac disease or inflammatory bowel disease

The bacteria are often the consequence. If we don't address why they were able to overgrow in the first place, relapse becomes much more likely.

SIBO treatment isn't one step

Many people expect treatment to be:

Take antimicrobials or antibiotics for four weeks → cured.

Unfortunately, this is rarely how the gut works. The bacteria may improve relatively quickly, but the environment that allowed them to overgrow often takes much longer to recover. This is why my treatment plans generally move through three phases.

hase 1: Reduce the overgrowth

(approximately 4–8 weeks depending on the phenotype)

This is the stage most people think of when they hear "SIBO treatment."

Depending on your breath test results, this may involve:

• herbal antimicrobials

• prescription antibiotics

• biofilm support where appropriate

• symptom management

• targeted probiotics in selected patients

• motility support

Importantly, the treatment is chosen according to the dominant gas pattern.

Hydrogen, methane and hydrogen sulfide overgrowths do not always respond to the same therapies, and newer research is increasingly moving towards phenotype-specific treatment both medically & naturopathically rather than one protocol for everyone.

What about diet?

One of the biggest misconceptions about SIBO is that you need to permanently eliminate large numbers of foods. I rarely recommend highly restrictive diets.

While reducing fermentable carbohydrates can temporarily reduce symptoms by limiting fuel for microbial fermentation, it does not treat the underlying reason the overgrowth developed. In fact, long-term restriction may further reduce microbial diversity, making recovery more difficult. Instead, I usually use dietary modification as a temporary symptom-management tool while treatment is underway, with a clear plan to gradually reintroduce foods as the gut heals.

The goal is always the most varied diet possible for you. Just like in human populations, the ocean, and the bush: diversity is the key to good health & longevity.

Phase 2: Repair and restore

Once the overgrowth has reduced, the real work begins. This stage often determines whether someone remains well six months later. Depending on the individual, treatment may focus on:

• repairing the intestinal lining

• restoring healthy digestive function

• improving stomach acid and digestive enzymes where indicated

• normalising bowel habits

• supporting bile flow

• rebuilding microbial diversity

• restoring the migrating motor complex (MMC)*

• improving gut motility with appropriate prokinetics

• reducing ongoing inflammation

This is the phase that is commonly skipped, yet it is often the difference between temporary improvement and long-term recovery.

*The migrating motor complex (MMC)

Between meals, the small intestine performs a housekeeping cycle known as the migrating motor complex. Think of it as the gut's internal cleaning system. It sweeps leftover food particles and bacteria down into the large intestine where they can be appropriately secreted. When this system slows or stops working, bacteria have an opportunity to remain in, or translocate to, the small intestine and multiply. This is why restoring the MMC is one of the most important strategies for reducing relapse. Due to the importance of the MMC, I often introduce this support early and continue it during all phases of treatment.

Phase 3: Maintain and prevent relapse

The final stage is not about taking supplements forever. It is about creating a gut environment where overgrowth is less likely to return.

This may include:

• expanding dietary diversity

• gradually reintroducing previously restricted foods

• maintaining bowel regularity

• supporting motility

• having a plan for sickness or relapse

• treating underlying medical conditions (e.g. thyroid, endometriosis)

• improving sleep, stress, and exercise

• maintaining a resilient microbiome

My goal is always to help you become less dependent on supplements over time, not more.

What about fructose malabsorption?

Many people are told they have fructose malabsorption and simply avoid huge groups of plant foods for years. In some cases, that diagnosis is correct.

However, fructose malabsorption can also occur secondary to SIBO. When excessive bacteria ferment fructose in the small intestine before it has a chance to be absorbed, breath testing may suggest fructose malabsorption even though the underlying problem is actually bacterial overgrowth. For some people, successfully treating the overgrowth significantly improves their tolerance to fructose-containing foods. This is another reason I prefer to identify the underlying cause rather than simply recommending lifelong dietary restriction.

SIBO is often only one part of the picture

Although treatment begins in the small intestine, I rarely think of SIBO as an isolated condition. Many people also have evidence of broader gastrointestinal dysfunction, including:

• reduced microbial diversity

• large bowel dysbiosis

• impaired short-chain fatty acid production

• intestinal inflammation

• altered bile acid metabolism

• fungal overgrowth

• parasites

• impaired digestive function

In other words, the entire gut ecosystem may need attention. The aim is not simply to "kill bacteria". The aim is to restore a healthy, resilient microbiome that naturally resists future overgrowth.

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