Why can some people eat whatever they like, whilst others struggle with bloating, stomach cramps and digestive issues even after eating healthy fruit, vegetables and wholemeal foods? We often put it down to stress or a sensitive stomach. Yet sometimes there is another culprit: bacteria in the wrong part of the digestive tract. Known as SIBO (small intestinal bacterial overgrowth), this condition may affect millions of people who have no idea that their digestive troubles are actually sibo symptoms.
Key takeaways in brief
- With SIBO (small intestinal bacterial overgrowth), bacteria migrate from the large intestine into the small intestine, where they do not belong.
- They ferment food prematurely—generating gases that trigger abdominal distension and bloating.
- Ironically, a healthy, high-fibre diet can actually worsen these symptoms.
- SIBO is usually diagnosed via a hydrogen breath test and managed through diet, antibiotics or botanical antimicrobials.
- Plant-based remedies such as oregano oil, berberine and allicin have demonstrated promising effects in clinical studies.
SIBO symptoms and bloating: what is really going on?
SIBO stands for small intestinal bacterial overgrowth. It occurs when bacteria migrate from the large intestine into the small intestine, where only relatively few bacteria should reside. These microbes ferment food—particularly carbohydrates—too high up in the digestive tract, far too early in the digestive process. This rapid fermentation produces hydrogen and methane gases that drive classic sibo symptoms like uncomfortable abdominal distension and trapped wind.
In addition, nutrient deficiencies can develop: the bacteria consume a proportion of nutrients before the small intestine has a chance to absorb them, whilst inflammatory processes further disrupt uptake. Iron and vitamin B12 are frequently affected. Fat digestion can also be compromised, reducing the effectiveness of digestive enzymes and impeding the absorption of fat-soluble vitamins A, D, E and K.
Causes of bloating: how SIBO develops
In most cases, several factors combine. The most common reasons for a bloated stomach and bacterial overgrowth include:
- Impaired self-cleaning mechanisms of the gut (migrating motor complex), triggered by conditions like diabetes, previous infections or chronic stress
- Leaving insufficient gaps between meals
- Sluggish gut motility (motility disorders)
- Anatomical changes following surgery or internal adhesions
- Reduced stomach acid, which allows more bacteria to survive and enter the small intestine
- Medications such as antibiotics that disrupt the natural balance of the gut microbiome
Because these issues overlap heavily with irritable bowel syndrome (IBS)—and both conditions can co-exist—distinguishing between them is often challenging.
SIBO breath test: how bacterial overgrowth is diagnosed
The most common diagnostic method is a specialised hydrogen breath test. Patients drink a solution containing lactulose, a sugar that the human body cannot absorb but bacteria readily consume. The test then measures the gases produced during bacterial fermentation in exhaled breath—specifically hydrogen and methane. A positive result confirms bacterial overgrowth in the small intestine.
Bloated stomach remedies: what helps with SIBO
A widely used dietary approach is the low FODMAP diet. This reduces specific, readily fermentable carbohydrates that lead to excess gas production—such as wheat products, pulses, dairy, certain fruits and particular sweeteners. Studies demonstrate that this can significantly relieve abdominal pain, bloating, flatulence, diarrhoea and constipation. In standard medical care, SIBO is typically treated with a targeted antibiotic such as rifaximin.
Natural remedies for SIBO
Botanical compounds have also been investigated—with remarkable results:
- Herbal blends (including oregano and thyme oil, berberine, wormwood): In one clinical study, 46% of patients achieved a negative breath test after four weeks, compared to 34% on antibiotics. Among those who did not respond to antibiotics, 57% tested negative after switching to herbal therapy.
- Berberine: Demonstrated an efficacy comparable to the standard antibiotic in a randomised controlled trial.
- Allicin (from garlic): Renowned for its broad antimicrobial action, though robust clinical trials focusing specifically on SIBO are still emerging.
- Probiotics (Saccharomyces boulardii): A beneficial yeast that competes with bacteria. When combined with antibiotics, 55% of patients tested negative, and significant symptom improvement was observed only in the probiotic group.
Faecal microbiota transplantation is also being researched, though it is not standard NHS practice in the UK. Crucially, SIBO can recur after successful treatment, which is why identifying and managing the underlying root cause is vital.
Summary
Persistent abdominal bloating is often more than just a sensitive stomach—it can be driven by small intestinal bacterial overgrowth. The frustrating reality is that otherwise healthy, high-fibre foods can actually exacerbate the problem. Fortunately, there are effective solutions available, from a low FODMAP diet and antibiotics to plant-based remedies like oregano oil and berberine. Because SIBO can recur, supporting gut motility and addressing the root cause is essential. If you experience persistent or severe sibo symptoms, always seek medical advice from a GP or gastroenterologist.
Frequently asked questions
What is SIBO?
Small intestinal bacterial overgrowth occurs when bacteria migrate from the large intestine into the small intestine. They ferment food prematurely and generate excess gas, causing abdominal distension and bloating.
Why is my stomach always bloated after eating healthy food?
In SIBO, bacteria in the small intestine rapidly ferment the fermentable carbohydrates found in fruit, vegetables and wholemeal foods, resulting in significant gas production.
How is SIBO diagnosed?
Usually via a hydrogen breath test: you drink a lactulose solution, and the levels of hydrogen and methane gases produced by bacteria are measured in your breath samples.
What is the low FODMAP diet?
An eating plan that restricts fermentable short-chain carbohydrates—such as wheat, pulses, dairy and certain sweeteners. It can substantially reduce digestive discomfort.
Do herbal remedies help with SIBO?
In clinical trials, herbal preparations containing oregano oil, thyme oil and berberine demonstrated effectiveness comparable or even superior to standard antibiotics.
Can SIBO return?
Yes. That is why ongoing management must address the underlying cause, such as sluggish gut motility or grazing without adequate fasting intervals between meals.
What is the difference between SIBO and IBS?
The symptoms overlap significantly, and both can be present at the same time. A hydrogen breath test can help determine whether bacterial overgrowth is an underlying factor.
Are probiotics beneficial for SIBO?
In a clinical study, the probiotic yeast Saccharomyces boulardii significantly improved symptoms, especially when taken alongside an antibiotic.
References and sources
Systematic reviews, meta-analyses and controlled clinical trials on this topic. Every link was verified for accessibility on 16/08/2026.
- Silva BCD, Ramos GP, Barros LL et al.: DIAGNOSIS AND TREATMENT OF SMALL INTESTINAL BACTERIAL OVERGROWTH: AN OFFICIAL POSITION PAPER FROM THE BRAZILIAN FEDERATION OF GASTROENTEROLOGY. Arquivos de gastroenterologia 2025. PubMed 39968993. DOI: 10.1590/S0004-2803.24612024-107.
- Sellge G, Ockenga J: [Small intestinal bacterial overgrowth (SIBO) – Therapy, nutrition, microbiome]. Deutsche medizinische Wochenschrift (1946) 2024. PubMed 39208859. DOI: 10.1055/a-2205-5794.
- Kashyap P, Moayyedi P, Quigley EMM et al.: Critical appraisal of the SIBO hypothesis and breath testing: A clinical practice update endorsed by the European society of neurogastroenterology and motility (ESNM) and the American neurogastroenterology and motility society (ANMS). Neurogastroenterology and motility 2024. PubMed 38798120. DOI: 10.1111/nmo.14817.
- Tansel A, Levinthal DJ: Understanding Our Tests: Hydrogen-Methane Breath Testing to Diagnose Small Intestinal Bacterial Overgrowth. Clinical and translational gastroenterology 2023. PubMed 36744854. DOI: 10.14309/ctg.0000000000000567.
