SIBO Nutritionist UK: Understanding SIBO and How Nutritional Therapy Can Support Recovery
Struggling with Bloating, Gas or Unexplained Digestive Symptoms?
If you've been dealing with persistent bloating, abdominal discomfort, excessive gas, constipation, diarrhoea or food sensitivities, you may have come across the term Small Intestinal Bacterial Overgrowth (SIBO).
Many people with SIBO are told they have IBS because the symptoms can overlap significantly. In fact, bloating, abdominal discomfort and altered bowel habits are among the most common symptoms reported in both conditions. However, SIBO and IBS are not the same condition and may require different management approaches.
As a nutritional therapist specialising in digestive health, I help clients explore the dietary and lifestyle factors that may be contributing to digestive symptoms and support them in developing a personalised plan for long-term gut health.
What Is SIBO?
Small Intestinal Bacterial Overgrowth (SIBO) occurs when there is an abnormal increase in the number or type of bacteria within the small intestine. The small intestine normally contains far fewer bacteria than the large intestine. When this balance becomes disrupted, digestive symptoms can occur.
Excess bacteria can ferment carbohydrates before they are fully digested, producing gases such as hydrogen and methane. This may contribute to symptoms including bloating, abdominal discomfort and changes in bowel habits.
SIBO is increasingly recognised in people with chronic digestive symptoms, although diagnosing and managing the condition remains an evolving area of gastroenterology research.
Common Symptoms of SIBO
Symptoms can vary significantly between individuals.
Common symptoms include:
Bloating
Persistent bloating, particularly after meals, is one of the most frequently reported symptoms of SIBO.
Excessive Gas
Hydrogen and methane gases produced by bacterial fermentation may contribute to excessive wind, belching and abdominal distension.
Abdominal Pain or Discomfort
Pain may range from mild discomfort to significant cramping.
Diarrhoea
Hydrogen-dominant SIBO is often associated with looser stools and diarrhoea.
Constipation
Methane-producing organisms are frequently associated with constipation and slower gut motility. Current guidelines increasingly refer to methane overgrowth as Intestinal Methanogen Overgrowth (IMO).
Nutritional Deficiencies
In some cases, bacterial overgrowth may interfere with nutrient absorption and contribute to deficiencies such as vitamin B12 deficiency.
What Causes SIBO?
SIBO is rarely caused by a single factor.
Current research suggests that underlying issues affecting digestion, gut motility or gastrointestinal structure often contribute to bacterial overgrowth. In many cases, several factors may be involved simultaneously.
Potential contributors include:
Impaired Gut Motility
The migrating motor complex (MMC) is often referred to as the gut's "housekeeping system." It helps clear bacteria and food debris from the small intestine between meals. Reduced motility may increase the risk of bacterial overgrowth by allowing bacteria to remain in the small intestine for longer periods.
Previous Gastrointestinal Infection
Some people develop digestive symptoms following food poisoning or gastroenteritis. Research suggests that post-infectious changes may affect gut motility and contribute to the development of SIBO in susceptible individuals.
Structural Changes
Previous abdominal surgery, adhesions, diverticula and anatomical abnormalities may increase SIBO risk by creating areas where bacteria can accumulate and multiply.
Reduced Stomach Acid
Stomach acid acts as an important defence mechanism against excessive bacterial growth. Reduced acid production may allow more bacteria to survive and enter the small intestine, potentially increasing the risk of bacterial overgrowth.
Certain Medical Conditions
Conditions such as diabetes, hypothyroidism, connective tissue disorders and other conditions affecting gut motility may increase the likelihood of developing SIBO.
Dietary Factors
Diet alone is not considered a direct cause of SIBO. However, dietary patterns may influence digestive symptoms and bacterial fermentation. Diets high in fermentable carbohydrates can sometimes worsen symptoms such as bloating, gas and abdominal discomfort in individuals with SIBO, although they are unlikely to be the underlying cause of bacterial overgrowth itself.
Antibiotic Use
The relationship between antibiotics and SIBO is complex. While certain antibiotics are used to treat SIBO, repeated or inappropriate antibiotic use may alter the balance of the gut microbiome and has been proposed as a potential contributing factor in some individuals. More research is needed to fully understand the long-term impact of antibiotics on SIBO development and recurrence.
SIBO vs IBS: What's the Difference?
SIBO and IBS share many symptoms, including:
Bloating
Abdominal pain
Constipation
Diarrhoea
Excessive gas
Because of this overlap, distinguishing between the two can be challenging. Some people diagnosed with IBS may also have SIBO, while others may not. Current research continues to investigate the relationship between these conditions.
Importantly, IBS is considered a disorder of gut-brain interaction, whereas SIBO refers to bacterial overgrowth within the small intestine.
How Is SIBO Diagnosed?
Diagnosing SIBO is not always straightforward.
Breath Testing
The most commonly used method is a hydrogen and methane breath test using glucose or lactulose substrates. These tests measure gases produced by bacteria after consuming a test solution.
SIBO and the Low FODMAP Diet
The Low FODMAP Diet is often discussed in relation to both IBS and SIBO.
FODMAPs are fermentable carbohydrates that can be rapidly utilised by gut bacteria. For some individuals, temporarily reducing high-FODMAP foods may help reduce symptoms such as bloating and gas. However, the Low FODMAP Diet is not considered a treatment for SIBO itself and should ideally be personalised and not followed unnecessarily long-term.
The goal should always be to maintain as varied a diet as possible while managing symptoms effectively.
Can Diet Help SIBO?
Nutrition can play an important role in symptom management and recovery.
Depending on the individual's situation, nutritional support may focus on:
Identifying symptom-triggering foods
Supporting nutritional adequacy
Managing bloating and digestive discomfort
Supporting bowel regularity
Developing sustainable eating habits
Supporting overall gut health
Many people with SIBO wonder whether certain diets can "starve" the bacteria responsible for their symptoms. While reducing fermentable carbohydrates may temporarily decrease the fuel available for bacterial fermentation and help reduce symptoms such as bloating and gas, diet alone is not generally considered a cure for SIBO.
Research suggests that dietary approaches may help manage symptoms by reducing fermentation and improving comfort, but addressing underlying factors such as gut motility, digestive function and any contributing medical conditions is often equally important.
For some individuals, strategies such as a Low FODMAP diet may provide symptom relief by reducing the amount of fermentable carbohydrates reaching the small intestine. However, these approaches are typically intended as short-term tools rather than permanent restrictive diets.
The goal of nutritional therapy is not to eliminate as many foods as possible, but to create a sustainable, nutritionally balanced way of eating that supports digestive health while minimising symptoms.
Dietary strategies should always be personalised rather than based on unnecessary long-term restriction.
How Nutritional Therapy Can Help
SIBO management often requires looking beyond food alone.
A personalised nutritional therapy approach may consider:
Symptom history
Medical history
Previous infections
Dietary patterns
Stress levels
Sleep quality
Digestive function
Supplements
Existing diagnoses
The aim is to support digestive health while helping clients avoid becoming trapped in increasingly restrictive diets.
Frequently Asked Questions
Is SIBO the same as IBS?
No. While symptoms overlap, IBS and SIBO are different conditions. Some people may have one condition, while others may experience both.
What are the most common symptoms of SIBO?
Common symptoms include bloating, excessive gas, abdominal pain, diarrhoea, constipation and changes in bowel habits.
Can SIBO cause nutritional deficiencies?
In some cases, bacterial overgrowth may interfere with nutrient absorption and contribute to deficiencies such as vitamin B12 deficiency.
Is a breath test necessary?
Current clinical guidelines generally recommend breath testing for symptomatic individuals when SIBO is suspected rather than relying on symptoms alone.
Can SIBO come back?
Recurrence can occur, particularly if underlying factors affecting digestion or gut motility are not addressed.
Ready to Take the Next Step?
If you're struggling with bloating, abdominal discomfort, constipation, diarrhoea or unexplained digestive symptoms, personalised nutritional support may help you better understand what is contributing to your symptoms and develop a sustainable approach to digestive health.
Book a free discovery call to discuss your symptoms and explore whether nutritional therapy may be right for you.
References
American Gastroenterological Association Clinical Practice Update: Diagnosis and Management of Small Intestinal Bacterial Overgrowth (2020).
American College of Gastroenterology. Small Intestinal Bacterial Overgrowth (SIBO), updated 2024.
Pimentel M, Saad RJ, Long MD, Rao SSC. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. American Journal of Gastroenterology. 2020.
Merck Manual Professional Edition. Small Intestinal Bacterial Overgrowth (SIBO), reviewed 2025.
StatPearls. Small Intestinal Bacterial Overgrowth. Updated 2025.
About Rosalie Collins
Rosalie Collins BSc (Hons) is a Nutritionist and Registered Nutritional Therapist specialising in IBS, bloating, coeliac disease and digestive health. She holds a degree in Nutritional Therapy and is registered with the British Association for Nutrition and Lifestyle Medicine (BANT) and the Complementary & Natural Healthcare Council (CNHC).
Drawing on both professional training and personal experience of living with coeliac disease and IBS, Rosalie supports clients with evidence-based nutritional therapy tailored to their individual needs.
Rosalie is based in Glasgow and Derbyshire and works with clients throughout the UK via online consultations, helping them understand the root causes of digestive symptoms and develop sustainable strategies for long-term gut health.
