SIBO - Small Intestinal Bacterial Overgrowth

Are your gut symptoms persistent?

Have you been told you have IBS, yet despite doing ‘all the right things’ your gut still feels unpredictable? Maybe you’re reacting to healthy foods, bloating after every meal, or feeling constantly drained? If you find it hard to tolerate a high-fibre diet or fermented foods it is worth considering whether you have Small Intestinal Bacterial Overgrowth (SIBO).

At Tree of Life Nutrition, we know that SIBO is often an overlooked cause of digestive issues. Or maybe you’ve been tested before, but haven’t had full resolution of symptoms? As experienced gut health dietitians, we have years of experience in helping patients in diagnosis, treatment and management of SIBO. We often work with patients who have complex cases to find the right answers, and work towards sustained solutions.

small intestinal bacterial overgrowth sibo
what is sibo

What is SIBO?

Small Intestinal Bacterial Overgrowth, or SIBO for short, occurs when bacteria from the colon normally kept in check within the small intestine grow in excess, or when bacteria typical of the large intestine migrate into the small bowel. When the bacteria proliferate in the case of SIBO, a range of symptoms can occur such as bloating, abdominal pain and diarrhoea.

In a healthy digestive system that’s functioning efficiently, the small intestine has relatively modest levels of bacteria. If you suspect SIBO, it’s more than a case of ‘too much bacteria’ – it’s often indicative of wider issues with gut function and digestion.

As experienced gut-health dietitians, we can help determine if SIBO testing is appropriate, interpret results of any test, manage a diagnosis of SIBO and implement long-term strategies to prevent recurrence.

Why does SIBO occur?

SIBO develops when the small intestine’s natural defences stop working as well as they should. Normally, your body prevents too much bacteria from building up through a number of important functions:

  • Production of stomach acid and bile that kills bacteria before they move further down the gut
  • Digestive enzymes that break down food and keep bacteria in check
  • Healthy gut movement (motility) pushing food and bacteria along at the right pace
  • The ileocecal valve – a “gate” between the small and large intestines that stops bacteria flowing backwards
  • Immune protection (IgA) that helps to keep the small intestine’s environment balanced

When any of these systems slow down or weaken, excess bacteria can be present where it shouldn’t be, leading to SIBO. Common reasons this can happen include:

  • Gut motility problems
  • Low stomach acid or reduced digestive enzymes
  • Certain medications
  • Structural or surgical changes in the gut
  • Removal or weakening of the ileocecal valve
  • Immune system conditions that reduce IgA levels

In simple terms, anything that slows the gut, changes its structure, or weakens its natural defences can allow bacteria to overgrow in the small intestine.

At Tree of Life Nutrition we always aim to identify and address why SIBO has developed, not just treat the overgrowth.

Do I have SIBO?

Persistent gut symptoms may be an indicator that you have SIBO, especially if those symptoms overlap with IBS, or haven’t improved with treatment for IBS. These can include:

  • bloating
  • gas
  • abdominal discomfort
  • diarrhoea or constipation

SIBO is also more common in people with gut motility issues, diabetes, connective tissue or neurological conditions, or a history of abdominal surgery. Another clue is when you feel worse with probiotics, fermented foods, increased fibre, or feel better after antibiotics. If you are experiencing other signs such as tiredness and fatigue, nutrient deficiencies, unintentional weight changes, nausea, feeling full quickly, or skin concerns like rosacea this may also point toward SIBO.

symptoms of sibo

Different types of SIBO

There are several forms of SIBO, each defined by the type of gas produced during bacterial overgrowth in the small intestine:

  • Hydrogen-dominant SIBO caused by bacteria that generate excess hydrogen during fermentation.
  • Methane-dominant overgrowth (IMO) driven by methane-producing organisms that slow gut motility.
  • Hydrogen sulfide SIBO involves microbes that produce hydrogen sulfide gas, often trickier to detect.
  • Mixed-type SIBO when more than one gas is elevated, indicating multiple microbial imbalances at once.

Each gas pattern reflects a different imbalance in the small intestine and responds best to specific treatment strategies. Identifying the type of SIBO helps your dietitian tailor the most effective protocol for clearing the overgrowth and restoring healthy gut function.

Diagnosing and treating SIBO

SIBO diagnosis requires specialised testing, but is it appropriate to test in your case? We help determine if testing is right for you. If a SIBO test is indicated, we can also interpret results, as well as assist in helping you manage any SIBO diagnosis. Most importantly, we can look to the cause of your SIBO diagnosis, and work on strategies to help prevent recurrence of symptoms.

1. Symptom screening and history.

Before you undergo any testing, we can take a full health history, including any factors that may increase your risk of SIBO, such as past surgery, or IBS. We also look at your symptoms and their patterns in detail. For instance – do gut symptoms improve with antibiotics? Do they worsen on probiotics or fermented foods? How do you feel after eating high-fibre foods?

2. Testing

It’s important to select the right test to determine whether you have SIBO to prevent unnecessary expense and ensure accurate diagnosis. There are a range of testing options available to you. The less invasive SIBO test is a breath test (hydrogen and/or methane). You can also undergo endoscopy. Importantly, a microbiome stool test (for the colon) doesn’t reliably detect small-intestinal overgrowth.

3. SIBO test referral and interpretation

As part of your consultation, we can refer you for the correct test, as well as interpret the results. This is done in the context of your history, risk factors and symptoms. From here, we can decide if SIBO is likely or if further investigation is required such as endoscopy or structural imaging.

4. Diagnosis and tailoring

If SIBO is diagnosed, or strongly suspected, we craft a treatment plan specific to your subtype (hydrogen vs methane vs mixed), your symptom profile, underlying causes and long-term prevention.

SIBO dieitians tree of life nutrition

Sustainable strategies for SIBO

As gut health dietitians with advanced experience in microbiome, motility and SIBO management, our focus is not just on short-term symptom relief, but long-term gut health and prevention of recurrence. Working with us is about more than “getting rid of” excess bacteria, but restoring lower-intestinal diversity and normalising motility so that your digestive health has every chance to function optimally. We’ll also coordinate your SIBO care, helping you understand testing, arranging referrals, interpreting results, and setting out a personalised plan for treatment.

While some solutions focus on restrictive diets, this is very hard to maintain long-term. Our emphasis is on effective treatment and correcting underlying causes. The aim is to work with you on a sensible dietary strategy, nutrient support and eventual re-introduction and normalisation of your diet.

Book a SIBO consultation

If you suspect SIBO, book a consultation with one of our dietitians to review your gut-health history, symptoms and risk-factors, and decide if SIBO testing is right for you. If appropriate, we’ll guide you through the test referral, interpret the result and implement an evidence-based SIBO protocol that’s focused on long-term resolution. Then we’ll work together on a prevention plan so you’re not just “managing” symptoms but truly restoring gut resilience.

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Frequently Asked Questions

Q: Does standard microbiome stool testing find SIBO?
A: No. Stool testing primarily reflects the colon, and cannot reliably detect bacterial overgrowth in the small intestine. Breath testing or small-bowel sampling is required.

Q: Are restrictive diets a solution?
A: Restrictive diets like low-FODMAP can help reduce symptoms temporarily, but our goal at Tree of Life Nutrition is identifying root causes, clearing overgrowth, restoring healthy gut ecology and supporting motility so you can return to more normal eating long-term. Research shows combining therapeutic diet with antimicrobial/antibiotic and motility-support improves outcomes.

Q: What is the recurrence risk?
A: Without addressing the underlying cause (for example motility issues, structural issues, anatomical changes) the risk of recurrence is significant. That’s why our protocol emphasises prevention and gut resilience.

Q: Will I need antibiotics?
A: Many cases do require antibiotics or targeted antimicrobials. Some approaches also include prokinetics (to improve motility), dietary strategies and microbiome restoration. We work with you to decide the best pathway.

Ready to get started?

Book a SIBO consultation