Our digestive system is home to billions of microorganisms, known as the gut microbiome. Many of them are essential to our health, but even so-called ‘good’ bacteria can cause trouble in the wrong place! Small intestinal bacterial overgrowth (SIBO) is a very common gastrointestinal condition that is characterised by too many microorganisms in the small intestine. Unlike the large intestine which contains a rich microbiome of billions of bacteria, yeast and protozoa, the small intestine typically has less than 10/4 organisms per millilitre and anything above this level can be considered SIBO. This overgrowth is not necessarily ‘bad’ bacteria as such but microorganisms in the wrong place, often with yeasts such as candida there as well.
SIBO damages the intestinal lining of the small intestine, and interferes with normal activity which results in malabsorption of nutrients such as iron and B12. It can cause inflammation of not only the digestive system but other other organs such as the brain, as these bacteria release endotoxins and inflammatory cytokines.
In healthy digestive systems, there are many features that keep the levels of bacteria are kept in check:
Adequate levels of stomach acid secretions help extract nutrients from food and kill off bacteria.
The wave-like movement of the migrating motor complex (MMC), the housekeeper of the small intestine, sweeps all the food, bacteria and other debris after the meal has been finished and nutrients absorbed.
The secretion of bile from the gallbladder (when we have a healthy gallbladder and make adequate bile) initiates the MMC, helps absorb nutrients and kills off unwanted bacteria.
IgA immunoglobulins in the mucous membranes of the small intestine fight bacteria and other pathogens when present in adequate levels.
A functional ileocecal valve, the one-way valve connection between the small intestine and large intestine that should stop bacteria in the large intestine microbiome from sneaking back up into the small intestine!
The risk factors of SIBO are related to a break down in the protective mechanisms that should protect the small intestine:
Low stomach acid (hypochlorhydria), bile and enzyme deficiency. Stomach acid is essential to digest nutrients and kill bacteria but low stomach acid is actually very common! Chronic stress, advanced age, poor diet and low nutrients can result in hypochlorhydria. A sluggish gallbladder or overworked liver will reduce the bile available to help the small intestine do its job. The use of medications such as antacids and proton pump inhibitors which lower stomach acid in an attempt to ease reflux leads to many problems in the gut ( SIBO causes reflux! ).
Slow motility: the small intestine should have high motility due to the migrating motor complex, a ‘housekeeping broom’ that sweeps out the debris of leftover food and bacteria after a meal.
There are a number of diseases associated with low motility including hypothyroidism, Parkinsons, postural orthostatic tachycardia syndrome (POTS) and Ehler Danlos syndrome. Medications such as opiates will slow motility. Trauma to the brain or spine will disrupt the vagus nerve and also slow motility.
Post-infectious irritable bowel syndrome (PI-IBS) is caused by a food-borne gastric infection, and is more commonly known as food poisoning, or ‘travellers' diarrhoea’. The most common bacteria that cause food poisoning are Shigella, Campylobacter, Salmonella, and E. coli. They release a toxin called Cytolethal Distending Toxin B, or CdtB for short. When it enters the body, the immune system fights back with an antibody called anti-CdtB. CdtB looks like vinculin, a naturally occurring protein critical for healthy gut function. Because CdtB and vinculin can look alike, your body can think it needs to fight back against vinculin, at which point it starts producing another antibody, anti-vinculin. The production of anti-vinculin is an autoimmune response and leads to nerve damage and slowing of the Migrating Motor Complexes (MMC), which predisposes the gut to SISBO.
Damage to the nerves in the gut: this is known as intestinal neuropathy and this increases the risk of SIBO. A common reason is type 2 diabetes, the hypomotility results in stasis and SIBO. One recent meta analysis found that twenty-nine percent of diabetic patients tested positive for SIBO, and the risk of SIBO in diabetic patients was 2.91 times higher than that in patients without diabetes (Feng, X., & Li, X. Q. (2022). The studies also found that the oxidative stress and release of inflammatory cytokines from SIBO likely accelerate the progression of diabetes.
3. Anatomical abnormalities of the digestive tract and physical obstructions that can lead to overgrowth include:
Inflammatory bowel disease such as Crohn's disease, and diverticular disease.
Adhesions post surgery, appendicitis or from endometriosis.
Dysfunction of the Ileocaecal valve, the one way valve between the small and large intestine.
The sheer number of organisms in the small intestine make it very difficult for the gut to deal with and symptoms occur both in the gut and other far reaching organs of the body. The bacteria feed on the carbohydrates we eat and produce metabolic waste as gases, and it is this methane and hydrogen gas that causes the digestive upset. Individuals will often experience:
abdominal pain and bloating
heartburn, or reflux and belching
altered bowel movements (constipation and / or diarrhoea)
nausea, vomiting
changes to nutrient absorption .
Many of the bacteria secrete endotoxins called lipopolysaccharides. These endotoxins are inflammatory to the brain and can result in:
fatigue, anxiety, panic attacks, brain fog and insomnia.
SIBO is also known to be associated with many other conditions including
Irritable bowel syndrome (IBS)
Mast cell activation syndrome (MCAS)
Coeliac disease
Rheumatoid arthritis
Fibromyalgia
Rosacea and eczema
Osteoporosis
Scleroderma
Many autoimmune conditions.
Testing for SIBO:
Firstly, a thorough, in-depth case history of signs and symptoms as well as analysis of lifestyle factors such as stress, sleep and diet is essential to differentiate SIBO from other conditions and check for ‘red flags’ that require a referral for immediate medical care.
Lactulose SIBO breath test is the gold standard for SIBO testing and determines if the bacterial overgrowth is hydrogen or methane dominant. Humans do not create hydrogen or methane, so detection on oral expiration indicates bacterial metabolism of carbohydrates. You'll need to be on a special diet for a few days beforehand and although you can do the test at home, having attempted it myself, I highly recommend having it done in clinic!
Complete diagnostic stool analysis (CDSA) gives an overview of the large intestine, and looks at many aspects of digestion, absorption and the microbial flora. It detects pathogenic bacteria, parasites and yeast that may be affecting gut health and immunity and therefore a predisposition to SIBO in the small intestine.
Genomic (DNA) testing can be extremely useful when a client presents with symptoms of what could be severe histamine intolerance such as severe food sensitivities, nausea, vomiting, tachycardia, low blood pressure, insomnia, anxiety or brain fog. This simple DNA test looks at genomic pathways of methylation detoxification and neurotransmitters such as serotonin, dopamine and histamine. We work on the intersection of gene variants and environmental impact, and it is a very powerful tool.
Treatment:
Once you have a SIBO diagnosis you take one course of antimicrobials or antibiotics and your gut will heal and you'll live happily ever after….. unfortunately, most likely not!!!
It is important to note that SIBO is not a disease entity in itself but a manifestation of a deeper issue. To treat SIBO we have to delve deep into discovering and healing the root cause!!
Don't spend money on expensive functional testing until you understand and practise the fundamentals of good digestion! If you are going to heal your gut you have to take time to eat a meal slowly, sitting down and chewing well to digest food and produce stomach acid. Meal spacing, with at least 3-4 hours between meals, allows the MMC to be activated. I talk a lot about the fundamentals because it's really important! I will also prescribe bitters, prokinetics and digestive enzymes to help the MMC along.
Support the detox pathways: Are you pooping properly every day at least once a day? Drinking enough water? Really looking after your liver and gallbladder? Supporting your lymphatic system? Are you engaging in daily exercise you love? Are you getting direct sunlight every day to reset your circadian rhythm? This is where gut (and hormone) health starts.
Check thyroid function. The gut and thyroid are intricately connected, and problems in one will show up in the other. Gut dysbiosis can cause thyroid dysfunction and hypothyroidism is a common cause of SIBO, as it slows the MMC.
Regulate the stress response and get enough sleep. Honestly, this is what it all comes down to. Chronic, systemic inflammation from gut dysbiosis and the resultant histamine reaction can cause terrible neurological effects on the brain such as anxiety and insomnia. Genomic pathway testing can help us understand how best to proceed with nutrition and supplementation. Ensuring you activate the parasympathetic nervous system and are in a state of ‘rest and digest’ when eating is essential for good digestion and absorption. Reset the vagus nerve with meditation, breath work, tapping, earthing etc.
Remove inflammatory foods, replace with a personalised food plan that limits carbohydrates as this starves the SIBO and this should give good symptomatic relief within weeks. I recommend the SIBO Bi-Phasic Diet by Dr. Nirala Jacobi. Also taken into account are any food sensitivities caused by histamine or oxalate intolerances. This gentle, anti-inflammatory eating plan will ease symptoms, heal the gut damaged by SIBO and allow proper nutrient absorption.
It's time to attack! Antimicrobials and antibiotics may be used to kill off bacteria, but again, get the fundamentals in place before this step, or the SIBO will be back, unfortunately relapse after treatment without addressing conditions is common!!
In conclusion:
SIBO treatment is complex, and requires a deep dive into assessing and managing underlying conditions, removing bacterial overgrowth, addressing nutrient deficiencies and healing the gut.
If you are struggling with any of these signs or symptoms, I would love to work with you. Contact me at www.bespokenutrition.com.au
References:
Feng, X., & Li, X. Q. (2022) The prevalence of small intestinal bacterial overgrowth in diabetes mellitus: a systematic review and meta-analysis. Aging, 14(2), 975–988. https://doi.org/10.18632/aging.203854).