If you’re researching SIBO symptoms and treatment options and wondering whether SIBO could be driving your digestive issues, you’re in the right place.
Small intestinal bacterial overgrowth is one of the most commonly missed drivers of chronic digestive symptoms. It’s also one of the most treatable when properly identified and addressed.
Here’s what you need to know.
What is SIBO?
SIBO stands for Small Intestinal Bacterial Overgrowth. It occurs when bacteria that should predominantly reside in the large intestine migrate into and proliferate in the small intestine, where they don’t belong in those numbers.
The small intestine plays a critical role in digestion and health. It is responsible for:
- Digestion of food and absorption of nutrients
- Housing beneficial bacteria that produce short-chain fatty acids, vitamin K, and folate
- Regulating immune system function and preventing infection
- Maintaining muscular contractions that move contents through to the large intestine
When bacterial overgrowth disrupts these functions, the downstream effects can be significant and wide-ranging.
SIBO and IMO — what’s the difference?
There are two main types of overgrowth worth understanding:
Hydrogen-dominant SIBO involves an overgrowth of bacteria in the small intestine that produce hydrogen gas. This is more commonly associated with diarrhoea, loose stools, and urgency.
Intestinal Methanogen Overgrowth (IMO) — previously called methane-dominant SIBO — involves an overgrowth of methane-producing archaea, particularly Methanobrevibacter smithii. Methane gas has been shown to directly slow gut motility and intestinal transit time, making IMO a significant and frequently overlooked driver of chronic constipation. It also increases contractile activity in a backward direction, further impeding elimination.
If your primary symptom is constipation that hasn’t responded to dietary changes or standard interventions, IMO is worth specifically investigating. Understanding the distinction between hydrogen SIBO and IMO is essential for effective SIBO symptoms and treatment decisions
How common is SIBO?
SIBO is more prevalent than previously recognised. Research suggests it may be present in a significant proportion of people with irritable bowel syndrome (IBS), with some studies finding it in up to 80% of those with IBS. It can also occur in people without any obvious risk factors.
What are the symptoms of SIBO?
SIBO symptoms vary depending on the type of overgrowth present and the individual. Common presentations include:
- Bloating — often worse after eating or later in the day
- Abdominal pain and cramping
- Constipation — particularly with IMO
- Chronic diarrhoea — more common with hydrogen-dominant SIBO
- Excessive gas and burping
- Nausea
- Increasing food reactions and intolerances
- Nutritional deficiencies — particularly B12, iron, and fat-soluble vitamins A, D, and E
- Chronic fatigue and weakness
- Restless legs
- Anxiety — via the gut-brain connection
- Skin conditions, including acne, rosacea, and eczema — via the gut-skin axis
The breadth of symptoms is one of the reasons SIBO is so frequently missed — many of these presentations are investigated and treated in isolation, without considering the gut as the underlying driver.
What causes SIBO?
Normal protective mechanisms prevent bacterial overgrowth in the small intestine. These include stomach acid production, the migrating motor complex (MMC) — the housekeeping wave that clears the small intestine between meals — immune function, and the ileocecal valve that separates the small and large intestine.
When one or more of these mechanisms is compromised, SIBO can develop. Common risk factors include:
- Low stomach acid
- Impaired gut motility — including MMC dysfunction
- Irritable bowel syndrome
- Inflammatory bowel conditions such as Coeliac disease or Crohn’s disease
- Previous bowel surgery causing scarring or adhesions
- Long-standing or poorly controlled diabetes
- A diet high in simple, refined carbohydrates
- Recurrent antibiotic use
- Medications, including proton pump inhibitors, opioids, and some antihypertensives. Post-infectious gut dysfunction — following food poisoning or gastroenteritis, Stress — which impacts gut motility and intestinal permeability
SIBO is generally a secondary condition, meaning there is usually an underlying driver that needs to be identified and addressed to prevent relapse.
SIBO symptoms and treatment — how is it diagnosed?
The most accessible and widely used method for diagnosing SIBO is breath testing. Three substrates are used in SIBO breath testing: lactulose, fructose, and glucose. Each has different properties and clinical applications. Lactulose travels the full length of the small intestine and is useful for detecting overgrowth throughout. Glucose is absorbed in the proximal small intestine and is more specific for proximal SIBO. Fructose is useful for identifying fructose malabsorption alongside bacterial overgrowth. In my practice, I commonly use lactulose and fructose breath testing, interpreted alongside a thorough case history and symptom picture.
Hydrogen breath testing identifies hydrogen-dominant SIBO. Methane breath testing (or combined hydrogen/methane testing) identifies IMO. I use both lactulose and fructose breath testing in my clinical practice, and interpret results alongside a thorough case history and symptom picture.
It’s worth noting that a stool test does not diagnose SIBO; however, certain markers in a comprehensive stool analysis can support the clinical picture and help identify relevant microbiome imbalances alongside SIBO.
Small bowel aspiration and quantitative culture remain the gold standard for diagnosis, though it is invasive and not routinely available in clinical practice.
How is SIBO treated?
Effective SIBO treatment involves four key principles:
- Addressing the underlying cause or driver
- Treating the overgrowth
- Providing nutritional support
- Preventing relapse
Treating the overgrowth may involve:
- Herbal antimicrobials — research has found that herbal antimicrobial protocols can be as effective as antibiotic treatment for SIBO, and may be preferable for some patients. Commonly used herbs include oregano, berberine, and allicin
- Antibiotics — rifaximin is commonly prescribed for hydrogen SIBO; a combination of rifaximin and neomycin may be used for IMO
- Elemental diet — a liquid diet that starves bacteria while providing nutrition has evidence for SIBO eradication
Diet during treatment is used to reduce symptoms and bacterial load. Commonly used dietary approaches include the low FODMAP, the SIBO Bi-Phasic diet, and the specific carbohydrate diet. It’s important to note that dietary approaches alone will not eradicate SIBO — they reduce symptoms and make treatment more comfortable, but antimicrobial treatment is required for eradication.
These diets are also not designed for long-term use. Prolonged restriction can reduce overall microbial diversity in the large intestine and reduce production of beneficial short-chain fatty acids, including butyrate.
Prokinetics — herbal or pharmaceutical agents that stimulate gut motility — are an important part of relapse prevention, particularly for those with underlying motility issues or IMO.
Nutritional support to address deficiencies in B12, vitamin A, D, E, and iron may also be required, depending on the severity and duration of the overgrowth.
What about relapse?
SIBO has a recurrence rate of approximately 45% within a year of treatment. This is why identifying and addressing the underlying driver is as important as treating the overgrowth itself. Without addressing what allowed SIBO to develop in the first place, the conditions for regrowth remain.
Relapse prevention strategies include prokinetic support, ongoing dietary awareness, stress management, and in some cases, further investigation into structural or motility factors.
When to Seek Professional Support for SIBO Symptoms and Treatment
SIBO is a complex condition that requires proper investigation and a treatment plan tailored to the individual. The type of overgrowth present, the severity of symptoms, the underlying drivers, and the presence of other conditions all influence the approach.
If you suspect SIBO may be driving your symptoms, the most important first step is accurate testing — followed by a treatment plan that addresses not just the overgrowth, but what caused it. Getting the right support for SIBO symptoms and treatment starts with accurate testing and a thorough case history.
Get Things Moving covers SIBO and IMO as drivers of chronic constipation in detail — including how methane production slows transit time and what to do about it. [Download your copy for $37 AUD]
As a naturopath with extensive experience in SIBO symptoms and treatment and overall gut health, I use breath testing, microbiome testing, and a thorough case history to identify what’s driving your symptoms — and build a plan tailored to your situation.