WHAT IS SIBO (Small intestinal bacterial overgrowth)?
SIBO or small intestinal bacterial overgrowth is when there is too much bacteria in your gut that produce a gas that causes symptoms including but not limited to bloating, gas, abdominal pain, nausea, dyspepsia (indigestion), and a change in bowel movements (diarrhea or constipation). There are 3 types of SIBO: Hydrogen SIBO, SIBO Sulfide, and Intestinal Methanogen Overgrowth (IMO):
1. Hydrogen SIBO is an overgrowth of bacteria in the small intestine including E. Coli and Klebsiella that causes either diarrhea or constipation.
2. SIBO Sulfide is an overgrowth of bacteria in the small intestine that produce sulfur gas and presents most commonly with diarrhea. Levels of hydrogen sulfide, as measured by a breath test, correlate with the severity of diarrhea. A study (PMID: 36114762) showed that IBS-D patients had higher breath hydrogen sulfide (H2S) that correlated with a higher relative abundance of H2S-producing bacteria, including Fusobacterium and Desulfovibrio spp.
3. IMO is an overgrowth of methane-producing archaea in the small and/or large intestines and presents most commonly with constipation. This condition was previously called “methane SIBO,” but methanogens are not bacteria (the “B” in SIBO) but are archaea, a group of single-celled organisms. The level of methane measured by a breath test correlates with the severity of constipation. A study (PMID: 36114762) showed that IBS-C patients had higher breath methane (CH4) levels that correlated with a higher relative abundance of stool methanogens, predominantly Methanobrevibacter, as well as higher absolute abundance of Methanobrevibacter smithii.
WHY DOES SIBO HAPPEN?
The most important thing to remember is that SIBO has A ROOT CAUSE.
The GI tract harbors the largest microbial population in the human body, with over 35 trillion bacteria. Most of the bacteria are in the colon and there is a homeostasis with a general population of “good bacteria”. This homeostasis is kept in check by many factors including stomach acidity, motility and secretions in the 19 feet of small intestine, and the ileocecal valve (ICV) as a mechanical barrier preventing backwards movement of the bacteria from the colon. Root cause analysis usually finds a problem with one of these factors including abnormalities in anatomy, motility, pH, medications and immune function and inflammation -and there can be multiple! Make an appointment with Dr. Ivanina for an individualized approach to find yours!
WHAT DOES SIBO DO TO YOUR BODY:
SIBO has significant consequences including multiple gut symptoms, malabsorption, vitamin deficiencies and brain fog. In SIBO, colonic type aerobic and anerobic organisms mainly Escherichia coli, Enterococcus spp., Klebsiella pneumonia, Proteus mirabilis, and Staphylococcus sp., Clostridia sp., Neisseria sp. and Streptococcus sp. are usually overgrown. These bacteria are in the wrong place (too upstream in your gut) and therefore prematurely ferment dietary carbohydrates and produce short-chain organic acids and gas causing gas, bloating and diarrhea after eating, usually a few hours after eating once the food clears the stomach and gets into the small intestine.
– CARBOHYDRATE MALABSORPTION: These byproducts can damage the gut brush border and reduce carbohydrate enzymes called disaccharidases, causing malabsorption of carbohydrates and further worsening symptoms.
– FAT MALABSORPTION: SIBO also leads to fat malabsorption and diarrhea by deconjugation of bile salts which in turn impairs normal fat digestion leading to impaired fat absorption, diarrhea and steatorrhea. The free bile acids formed in this reaction leads to toxic injury to mucosa. Fat malabsorption due to SIBO could lead to deficiencies in fat soluble vitamins of A, D and E and less likely vitamin K because it is produced by bacterial metabolism.
– VITAMIN B12 DEFICIENCY: Gram-negative bacteria compete with your own body to use B12 from food so that you have none left to absorb for yourself! On the other hand, folate is generated by bacterial metabolism and is absorbed in abundance by the host so seeing a high folate is typical in SIBO. Other deficiencies include vitamin D and iron.
– BRAIN FOG. Recently, d-lactic acid production from bacterial metabolism in the human gut has been associated with metabolic changes and brain fog, especially in patients taking probiotics while having SIBO. This is why it is often not recommended to take probiotics while having active SIBO but instead to treat it and then rebuild and restore the microbiome first through probiotics in food, and then to consider probiotic supplements.
– There can be many other consequences of SIBO- especially in the presence of increased intestinal permeability (“leaky gut”) and therefore systemic symptoms like skin manifestations and rashes!
HOW TO DIAGNOSE SIBO
The gold standard is the sterile small intestinal aspirate done during upper endoscopy which is done by Dr. Ivanina in NYC. Small intestinal fungal overgrowth (SIFO) culture is performed at the same time. The test results tell you which bug grows and which antibiotic it is to!
To note- the aspirate does NOT culture methanogens or hydrogen sulfide pathogens as of yet.
The most common way to diagnose SIBO is through a breath test- with either lactulose or glucose substrate. Lactulose usually over-diagnoses so you don’t miss any SIBO and glucose usually under diagnoses but is more accurate.
Also to note- the only current way to diagnose SIBO Sulfide is through the TRIO SMART breath test.
HOW TO TREAT SIBO
1. Root cause analysis: Make sure you get a full workup for underlying causes of SIBO including lab testing, stool testing, endoscopic evaluation, and possibly other important testing such as IBS SMART after an infection (you sometimes don’t even realize you had an infection! example- one or two days of diarrhea that you brushed off to “something you ate”), and a motility test pill that measures stomach, small bowel and colonic transit as well as stomach acid!
2. Induction with antibiotics or antimicrobials: Hydrogen SIBO is usually responsive to one antibiotic while IMO requires dual antibiotic therapy to target hard to reach/treat methanogens. Alternatively, there are natural herbal antimicrobials you can discuss with your gastroenterologist. Elemental diet is reserved for extreme cases when everything else failed. There is no study that shows any other type of restrictive diet can treat SIBO and many times a restrictive diet is just a bandaid– or even worse, leads to disordered eating. Diet does play an important role in SIBO after induction therapy to prevent recurrence. There is no study that shows probiotics can treat SIBO but studies show that probiotics in active SIBO can cause brain fog. Therefore you need to find your own individualized approach with Dr. Ivanina based on the severity of your symptoms and approach you are looking for
3. Maintenance with prokinetics: Most cases of SIBO have a motility component, for example a disordered migrating motor complex (MMC) in the small bowel after infection and/or inflammation. The MMC is your housekeeper wave that keeps your small intestine clean and SIBO free- it is KEY to optimize this function with prokinetic medications, herbs and time restricted feeding (fasting periods). Diet also plays a key role after induction therapy including low-fodmap, low fodmap “light”, or low fermentation diet to prevent the recurrence of SIBO after treatment as SIBO very frequently will recur without proactive action.
WILL SIBO EVER GO AWAY?
SIBO can be a temporary state of dysbiosis that requires only supportive care or in RARE situations it can be permanent such as in the setting of ileocecal valve removal. Make sure to work closely with Dr. Ivanina to understand your root cause which will help you understand what to expect.