What is SIBO?
Small Intestinal Bacterial Overgrowth (SIBO) happens when too many bacteria build up in the small intestine, leading to uncomfortable gut symptoms and, in some cases, nutrient deficiencies.
I work with clients to help them understand what is driving their symptoms, calm inflammation, and make practical changes so you can eat with more confidence again.
What is SIBO?
SIBO is essentially an overgrowth of bacteria in the small intestine, where normally only relatively low numbers of microbes should be present. This overgrowth can interfere with digestion and absorption, leading to gas production, irritation of the gut lining, and problems with how you process fats, carbohydrates, and some vitamins.
• The excess bacteria ferment carbohydrates, producing hydrogen and/or methane gas, which drives bloating, pain, and changes in bowel habits.
• Over time, SIBO can contribute to malabsorption of nutrients such as vitamin B12, fat-soluble vitamins (A, D, E, K), and minerals like calcium.
Common SIBO symptoms
SIBO symptoms can overlap with IBS and other digestive issues, which is one reason it often goes undiagnosed for a long time.
Typical digestive symptoms include:
• Bloating and visible abdominal distension, often worsening after eating
• Excess gas, belching, and flatulence
• Abdominal discomfort or cramping
• Diarrhoea, constipation, or alternating between the both at differing times
• A feeling of fullness very quickly or discomfort after eating small amounts
Possible whole-body symptoms include:
• Unintentional weight loss or difficulty maintaining weight.
• Fatigue, weakness, and “brain fog” linked to nutrient deficiencies.
• Signs of low B12 or vitamin D over time, such as tingling, low mood, or bone health issues.
What causes SIBO?
SIBO is usually the result of something affecting how food and bacteria move through the small intestine or how well the gut’s natural defences are working.
Key contributors can include:
• Sluggish gut motility (slow movement of food), which might be linked to diabetes, connective tissue conditions, hypothyroidism, or nerve issues.
• Structural changes in the gut, such as adhesions, diverticula, strictures, or previous abdominal surgery that creates “pockets” or slows transit of food.
• Reduced stomach acid or bile flow, which would normally help keep bacterial numbers in check.
• Long-term use of certain medications, such as some acid-suppressing drugs, which can alter the gut environment.
• Co-existing conditions like coeliac disease, Crohn’s disease, or scleroderma that change how the small intestine functions.
How SIBO is usually diagnosed
Diagnosis is typically done by a gastroenterologist or specialist, and a nutritional therapist will often work alongside this medical process.
Common approaches include:
• Breath testing (usually lactulose or glucose) to measure hydrogen and methane gases produced by bacteria in the small intestine.
• In more complex cases, small bowel aspirate and culture, or investigative endoscopy, to directly sample small intestinal contents.
• Blood tests for nutrient levels (like B12, iron, and vitamin D) and markers of malabsorption if symptoms suggest deficiencies.
What to expect from working with me
Working with me when you have a SIBO diagnosis is not just about “what to eat” but about understanding your underlying triggers, supporting medical treatment, and helping you rebuild a more resilient gut over time.
The process:
• Firstly, I take a detailed health and symptom history: looking at your digestion, energy, previous diagnoses, medications, stress levels, and diet to identify patterns and possible root causes.
• I support you with access to testing if necessary and explain any results you already have that may be complicated and confusing: I help you understand breath test options, timing, preparation, and how test results might link to your symptoms (while diagnosis itself remains medical).
• I make a phased nutrition plan for you: starting with a plan to reduce symptoms (often adjusting fermentable carbohydrates, meal timing, and texture), then gradually re-expanding your diet to avoid long-term unnecessary restriction.
• Gut motility and digestion support: using food timing, fibre types, hydration, and sometimes carefully selected supplements (where appropriate) to support stomach acid, bile flow, and the migrating motor complex.
• Nutrient repletion: identifying where SIBO may have led to low B12, iron, or fat-soluble vitamins and using food-first strategies, with supplements if needed, to rebuild levels safely.
• Longer-term relapse prevention: gradually I will help you to broaden your diet, to support gut microbiome balance in the large intestine, and I will also work with you on lifestyle factors such as stress, sleep, and gentle movement, which all influence gut motility.
For many people, the most valuable parts of this process are having a clear plan, feeling understood, and no longer guessing which foods are “safe” day to day. I can help you move from constant firefighting of symptoms to a more stable, flexible way of eating that supports both your gut and overall health.