WHAT IS SIBO

SIBO (short for Small Intestinal Bacterial Overgrowth) is exactly that - an overgrowth of bacteria in the small intestine. So what exactly does that mean? Well, we all have a microbiome – a large clump of bacteria, fungus, virus etc – with the majority residing in our colon. This microbiome is very large and plays a huge role in our health – and not only within the digestive tract. To put it in perspective, it is thought that our bodies house ten times the amount of bacterial cells to human cells. That’s a lot of bacteria! And more than that, we know our bacteria can cross-talk with other important things in our body (such as hormones, neurotransmitters etc) which can affect certain things in the body such as metabolism, the nervous system and the immune system.  

How does SIBO fit in to all this?

Most of your bacteria are found in the large intestine with a very small amount which resides in the small intestine. Small Intestinal Bacterial Overgrowth is exactly as it sounds – an imbalance or overgrowth of bacteria in the small intestine which can lead to various issues, depending on what type of bacteria it is! We all have a small amount of bacteria which naturally resides in our small intestine – even healthy people. An overgrowth or imbalance in the types of bacteria (especially displaced bacteria from the colon) can lead to various symptoms and long term issues for people. This is due to the bacteria fermenting certain foods which would normally be fermented in the large intestine.

Carbohydrate fermentation in the small intestine is often the most common, (although in some people the type of bacteria present can cause issues with fats – it all comes to down to the type of bacteria). If people are having issues with carbohydrates – a common treatment is to go on a low-FODMAP diet, as this removes a lot of these particular foods which ferment and cause the symptoms. However, a long term FODMAP diet is not a great solution – as it cuts out a large portion of a person’s diet which may cause nutritional deficiencies and never actually deals with the underlying problem – the overgrowth of bacteria.

What are the symptoms?

The most common symptoms include bloating (one of the most common things I hear in clinic is people telling me they wake up with a flat tummy, but by the end of the day they feel pregnant), gas, abdominal pain, diarrhea and/or constipation. Some people get other symptoms such as nausea, reflux, skin rashes and fatigue. SIBO is often concomitant with a large number of other disease states – such as coeliac disease, inflammatory bowel disease, chronic fatigue syndrome, obesity, fatty liver disease, endometriosis etc. SIBO is, however, a relatively new condition recognised by the medical community and is therefore still often overlooked or remains undiagnosed. In some studies – more than 50% of IBS sufferers were found to have SIBO (some studies found up to 78%!). So for those suffering IBS – there’s more than a 50% chance that SIBO may be involved.

What are some of the common causes of SIBO?

There are various causes of SIBO – and often you will find it is a range of causes as opposed to one specific cause. Common causes can include dysbiosis of the microbiome (a significant imbalance of “bad” bacteria vs “good” bacteria), high antibiotic use in the past (especially broad-spectrum antibiotics), certain medications (such as proton pump inhibitors), digestive deficiencies (such as low stomach acid, low digestive enzymes/bile – all often associated with “sluggish” digestion), a weakened ileocecal valve (the valve between the small intestine and the large) which allows the transference of bacteria to travel backwards into the small intestine.

How is it diagnosed?

Unfortunately there is no perfect test to diagnose SIBO, as they all have limitations. You can get a breath test done (lactulose and/or glucose) which measures 2 specific gases on the breath – hydrogen & methane (which are by-products of fermentation by certain bacteria). It doesn’t pick up all SIBO and often results have to be determined in regards to varying factors (speed of digestion, onset of symptoms and many more). However, it is relatively cheap and easy to do (you do the breath test at home and send it off to be analysed) and if you have a practitioner who understands SIBO and is experienced in treating it, it can be extremely useful.

The second option includes endoscopy and culture testing which is more invasive (and often more expensive). In my clinic, I tend to use the breath test and, if combined with the microbiome testing (which can give some idea of the types of bacteria that may be causing SIBO – but cannot be used to diagnose SIBO alone) – I find this works well for most clients to get an accurate picture of the type of SIBO and how to treat it.

Treatment?

In some cases, specific antibiotics work well to treat SIBO. This would be prescribed by a GP or gastroenterologist. However, in other cases the SIBO can be caused due to an over-abundance of antibiotics in the past and not all bacteria will respond to antibiotics. Therefore, a much more comprehensive plan is required (using diet, supplements etc) to treat the underlying causes of SIBO.

Either way – whether using antibiotics or natural approaches – a key aspect of treatment involves improving the state of the microbiome, treating nutritional deficiencies and working on overall function of the digestive tract through various dietary, lifestyle and supplemental ways. There is no one diet which fits all, as not every person is dealing with the exact same type of SIBO.

References:

Compare, D et al 2011, ‘Effects of long-term PPI treatment on producing bowel symptoms and SIBO’, European Journal of Clinical Investigation, vol. 41, no. 4, pp. 380-386, https://www.ncbi.nlm.nih.gov/pubmed/21128930

Ghoshal, U C et al 2017, ‘Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy,’ Gut and Liver, vol. 11, no. 2, pp. 196-208, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5347643/

Grace, E et al, HN 2013, ‘Review article: small intestinal bacterial overgrowth – prevalence, clinical features, current and developing diagnostic tests, and treatment’, Alimentary Pharmacology and Therapeutics, no. 7, pp. 674-688, https://www.ncbi.nlm.nih.gov/pubmed/23957651

Hadar, N et al 2015, ‘Microbial endocrinology: the interplay between the microbiota and the endocrine system,’ FEMS Microbiology Reviews, vol. 39, no. 4, pp.509-521, https://academic.oup.com/femsre/article/39/4/509/2467625