Small intestinal bacterial overgrowth, or more commonly known as SIBO, has made its way around the block and recently arrived into the spotlight of gut health and IBS. It’s thought to be responsible for gut symptoms in a variable subset (between 4-78%) of individuals with IBS. But, what’s the deal with SIBO? What is it? And is there a relationship between IBS and SIBO? All these questions AND MORE will be answered in today’s blog.
First and Foremost, What is SIBO?
Small intestinal bacterial overgrowth (SIBO) is a condition that is characterised by an abnormally large number of bacteria growing in the small intestine; where this bacteria would normally grow in other parts of the gut. Due to this imbalance and gut bacteria being where it is not supposed to be; SIBO can cause some unwanted symptoms such as increased pain and altered bowel habits which may occur after eating. Unlike IBS, SIBO can cause weight loss and even develop into malnutrition as the bacteria will start to use up the body’s nutrients rather than being absorbed into the body.
There are certain individuals who are at a higher risk of developing SIBO, including those who have:
- Recently had a foodborne illness
- Inflammatory bowel disease
- Gut motility issues
- Low stomach acid levels
- IBS-D subtype (when compared to other subtypes)
SIBO vs. IBS – Is There a Relationship Here?
There is a considerable overlap between symptoms of IBS and SIBO such as:
- Abdominal pain
- Bloating
- Flatulence
- Diarrhoea and/or constipation
The overlap makes it difficult to differentiate between the two, additionally making it harder to determine which comes first and if one causes the other. There’s also conflicting reports on whether SIBO is more common in IBS. Research shows that SIBO is thought to affect anywhere between 0-20% of non-IBS sufferers compared with 4-78% IBS sufferers; the lack of consensus around diagnosis explains this wide variation. Based on this prevalence, there is some research supporting a link between IBS and SIBO, however a true relationship cannot be determined until more definite research is needed. 
How am I Diagnosed?
SIBO, for the most part is still being understood, with new research always evolving. Prevalence is not well known as there is a lack of consensus regarding its exact definition and diagnostics as there is no gold standard to diagnose SIBO.
Currently, the best method in diagnosing SIBO is via sampling small intestinal aspiration (fluids) and culture to assess whether a high amount of bacteria is present. Whilst traditionally thought to be the most accurate, it is quite invasive and costly to the patient and will only pick up SIBO in only one section of the small intestine.
An alternative and non-invasive test is hydrogen and methane breath testing and is more widely used in clinical practice. It relies on the principal that if bacteria are present in the small intestine, these will rapidly ferment carbohydrates consumed, leading to an early rise in breath hydrogen level when compared to if the carbohydrates were fermented in the large bowel.
Stream Diagnostics tests for SIBO.
How to Treat SIBO?
There are various different mechanisms for management of SIBO, where different lines of treatment may be considered.
The first line therapy with the most (albeit variable) research is antibiotic therapy; with the best evidence based approach is rifaximin that works predominately within the gut. Studies have shown an improvement in IBS related symptoms. Whilst antibiotics may improve symptoms in IBS and SIBO, there is uncertainty as to whether these antibiotics are acting on bacteria in small or large intestines with dysbiosis of large intestine also seen in IBS. Optimal dosing, mechanism and impact on repeated treatment are all yet to be determined, as further research is needed.
Probiotic formulations have also been considered in the treatment of SIBO in relation to IBS, however only a number of high quality studies exist, showing variable results. Albeit there are preliminary studies to suggest prebiotic supplementation enhances the effectiveness of antibiotic treatment, where combination therapy may be useful.
Key Note: It is important to actively treat SIBO when diagnosed, failure to do so can impact the function of the digestive system and ultimately lead to malabsorption and nutrient deficiencies along with causing more generalized inflammation.
Does Diet Have a Piece in This Puzzle?
Currently, there’s no consensus on a dietary therapy or recommendations to treat SIBO. Most of the suggested dietary therapies, such as the specific carbohydrate diet or the GAPS diet are either based on anecdotal evidence or individual studies; with the current gold standard for treatment is antibiotic therapy as suggested above.
However, in addition to other therapies, a combined dietary approach has been suggested involving the use of an elemental diet (replacing food and drinks with special liquid formulas) to eradicate SIBO; followed by low FODMAP diet approach as a maintenance phase. Much more research is needed.
For those not familiar with the low FODAMP diet, check out our blog post FODMAPs For Beginners – The FODMAP Diet Basics! for a quick run-down.
As always it’s recommended to follow the Nutritional guidelines that apply to you; with the general recommendations to have a diet inclusive of a wide variety of whole foods.
What if The Low FODMAP Has Stopped Working?
Unfortunately, the recurrence rate of SIBO is at about 50%, and whilst there are treatments, they’re not consistently as effective as desired. Like in the case of IBS, there are also individuals who don’t respond to the low FODMAP diet or after a period of time might not respond or find they need to re-implement the elimination phase of the low FODMAP diet to achieve symptom control again.
Other than the low FODMAP diet, some other dietary approaches that have been found to help manage SIBO are:
- Ensuring adequate fluid throughout the day
- Incorporating probiotic rich foods such as: yoghurt, certain pickled vegetables such as sauerkraut and tempeh.
- Addressing other types of intolerances that may come up, such as lactose and fructose intolerances.
As it is the bacteria overgrowth causing the symptoms, it could be as easy as treating the root cause, but the research and our understanding is just not there at the moment. However, this gap is slowly being reduced with new studies coming our regularly.
I Don’t Have Food Sensitivities…Do I Have to Re-introduce FODMAPS?
Unlike allergies, intolerances and sensitivities can change over time and in response to different events. Even without IBS, the dysbiosis and then antibiotic therapy used to treat SIBO could potentially trigger sensitivities.
It is usually best practice to follow all phases of the low FODMAP diet for optimal success (with some exceptions) on the diet, the re-introduction and then maintenance phase can provide you with the knowledge of what FODMAPs might trigger you and can ensure your diet remains as diverse and less restrictive as possible. Like stated earlier, IBS and SIBO tend to overlap and there may be an underlying IBS at play.
Especially if antibiotics are used, it can cause disruption in good gut bacteria that assist in the digestion of these FODMAPs.
Whilst FODMAPs can contribute to some uncomfortable symptoms with SIBO, complete elimination can potentially be detrimental to gut health; where a lot of FODMAP containing foods are also prebiotics. So, it’s important to go through all phases to work out your tolerance to maximise your diet with as little symptoms as possible.
In Conclusion…
SIBO is a condition characterised by bacteria overgrown into the small intestine which is accompanied by some uncomfortable gut symptoms and potentially even lead to nutrient deficiencies. Both its diagnosis and treatment is still being understood, meaning it can be misinterpreted for other gut conditions. Currently, antibiotic therapy is first-line treatment, where probiotics and even diet have also been found to play a role.
If you have been diagnosed with SIBO with or without IBS and want to try diet therapy, seek out a Gut Health and FODMAP-trained Dietitian for individualised support.
Written by: Lauren Theodore (Accredited Practising Dietitian)
