WHAT IS 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
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.
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.
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
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