We are increasingly aware that our microbiota plays a remarkable role in our health since it not only influences intestinal transit but is also related to the immune, endocrine and urinary systems, etc. It may even be involved in the development of cancer. Due to different factors, our microbiota can suffer alterations that affect its diversity and/or the quantity of microorganisms that form it, initiating a pathological process called bacterial overgrowth or SIBO.
If you have not yet heard of this alteration, pay attention because it is estimated that up to 35% of the general population may suffer from bacterial overgrowth, and the prevalence may increase up to 80-90% in patients with Irritable Bowel Syndrome or Chronic Fatigue Syndrome.
In the following lines I will try to present the knowledge we have so far based on information extracted from scientific articles and clinical practice.
What is SIBO?
Under normal conditions the small intestine should not harbor practically no bacteria, since it is an area dedicated to the digestion and absorption of nutrients. On the contrary, in the colon we should find a rich and diverse intestinal microbiota, reaching 109-1012 CFU (colony forming units).
Bacterial overgrowth, known as SIBO (small intestine bacterial overgrowth), is considered to be the excess of bacteria in the proximal small intestine, above 105 CFU. Some recent studies even question the figure, considering the diagnosis as from 103 CFU.
As far as we know, there are 3 types of SIBO:
- Hydrogen. It occurs mainly when there is excessive proliferation of bacteria.
- Methane. It occurs when there is an overgrowth of methanogenic archaea. This type of SIBO is also called IMO (intestinal methanogenic overgrowth).
- Sulfate. This type of SIBO is still under investigation.
What are the symptoms of bacterial overgrowth? Clinical manifestations.
Colonic bacteria migrating from their natural habitat, the colon, to the small intestine will cause discomfort in the affected person. The cells of the intestine will compete with the bacteria for food and this will cause different alterations:
Intestinal alterations derived from the accumulation of gas.
Caused by the fermentation carried out by bacteria and archaea, gastrointestinal discomfort will occur:
- Abdominal distention.
- Bloating (often the belly reminds the belly of a pregnant woman).
- Abdominal pain.
- Flatulence.
- Meteorism.
- belching
- Acidity.
- Alterations of the intestinal transit: Constipation or decomposition (depending on the microorganisms present in the small intestine). Even steatorrhea.
Derived from the production of toxic metabolites (endotoxins, bacterial compounds, etc.).
Produced by the increased microbiota, which promote the production of proinflammatory cytokines. These will damage the microvilli of the intestinal mucosa (where we absorb nutrients) causing inflammation in the intestine and malabsorption, increasing the risk of:
- Nutritional deficiencies, being the most common deficiencies of vitamin B12, vitamins A, D, E and iron. Anemia or nervous system alterations may appear, for example. Folate and vitamin K levels are generally normal or high, given the ability of bacteria to synthesize them.
- Food intolerances: fructose, sorbitol, lactose, other carbohydrates, histamine, gluten, etc. depending on the enzymes and transporters that are affected, due to the damage of the intestinal mucosa.
- Asthenia, caused by nutritional deficits.
- Weight loss, caused by malabsorption and gastrointestinal symptoms that may cause lack of appetite or avoidance of food due to the discomfort that usually appears after ingestion.
- Increased risk of Candida and other yeast infections.
Derived from not attending to and not treating the above symptoms for a long time
The junctions between the enterocytes may be broken, resulting in intestinal permeability (leaky gut). In this situation the contents of the intestine can come into contact with the immune system and cause systemic inflammation, increasing the probability of the appearance of autoimmune diseases (Crohn’s disease, ulcerative colitis, etc.), allergies, dermatological and neurological conditions or insulin resistance, among others.
Causes of SIBO Why does it appear?
There are several reasons that can lead to pathological microbiota proliferation in the small intestine. I will try to summarize them below:
Anatomical causes
- Alterations in the ileocecal valve or Bauhin’s valve. When the “door” that separates the large intestine from the small intestine is left open (open ileocecal valve syndrome), it is more likely that SIBO will appear. This alteration has several possible causes:
- Intestinal surgeries.
- Short bowel syndrome with absence of this valve.
- Inflammatory bowel diseases (Crohn’s, Ileitis…) affecting the Bauhin valve.
- Stress.
- Blind loop syndrome. In which part of the small intestine forms a bag or loop in which food stagnates being an ideal environment for the microbiota to proliferate. It can be caused by:
- Abdominal surgeries (gastric by-pass, gastrectomy…).
- Intestinal adhesions.
- Abdominal radiotherapy.
- Presence of fistulas.
- Diverticulosis.
- Etc.
- Other
Deficiency of gastric acid, bile and/or digestive enzymes.
These have bacteriostatic properties, they prevent colonic bacteria from reaching the stomach and intestine. When their quantity is depleted, there is a greater likelihood of colonization of the microbiota in these portions of the digestive tract. What can cause these deficits?
Conditions that cause decreased or absent hydrochloric acid in the stomach (hypochlorhydria/achlorhydria):
- Older age.
- Use of proton pump inhibitor drugs or hydrogen receptor antagonists, misnamed gastric protectants or antacids, which are commonly used to treat heartburn caused by gastroesophageal reflux. Examples of these drugs are Omeoprazole or Ranitidine.
- Chronic atrophic gastritis (secondary to Helicobacter pylori infection or autoimmune causes).
- Pernicious anemia.
- Treatment with radiotherapy.
- Gastric bypass.
- Etc.
Conditions that cause decrease of bile (cholestasis):
- Choledocholithiasis (stones in the gallbladder that obstruct the flow of bile acids).
- Cholangitis (inflammation of the bile ducts).
- Choledochal cyst.
- Pancreatitis.
- Neoplasm in the head of the pancreas or bile ducts.
- Use of some drugs.
- AIDS.
- Biliary cirrhosis.
- Toxic, viral or autoimmune hepatitis.
- Caroli’s disease.
- Byler’s disease.
- Parasites.
- Duodenal diverticulum.
- Etc.
Conditions leading to digestive enzyme deficiency (lipases, peptidases, amylases):
- Older age.
- Alterations in the salivary glands.
- Pancreatic pathologies (pancreatitis, obstruction, cancer…).
- Hepatic disorders.
- Crohn’s disease.
- Cystic fibrosis.
- Cystic fibrosis. Etc.
Decreased intestinal motility (bowel movements).
In normal conditions our intestine carries out two types of movements:
- Those associated with food intake.
- Those associated with fasting periods, known as the migratory motor complex (MMC). These movements are activated between 2 and 4 hours after ingesting food and are extremely important as their function is to keep the lumen of the small intestine clear and “clean” of bacteria from food, thus reducing the risk of microbiota overgrowth.
One of the clearest symptoms of poor motility is constipation, so looking for its cause and treating it can prevent the onset of SIBO.
There are several situations in which worse motility can occur:
- Older age.
- Consumption of certain drugs or medicines (anticholinergics, antidiarrheals, opiates such as morphine or codeine, etc.).
- Various pathologies: Hypothyroidism, autonomic neuropathy due to diabetes, Parkinson’s disease, scleroderma, radicular enteritis, polymyositis, amyloidosis, multiple sclerosis, celiac disease, inflammatory bowel disease (Crohn’s disease, ulcerative colitis), short bowel syndrome, obesity, etc.
- Lack of physical activity: advanced age, very marked overweight (morbid or extreme obesity), bedridden people, people with hemiplegia/paraplegia, people with chronic fatigue syndrome and/or fibromyalgia who have great difficulty in moving…
- Some dietary behaviors: diet poor in fiber, chewing gum or consuming stevia.
- Etc.
Autoimmune pathologies
Scleroderma, type 1 diabetes mellitus, ulcerative colitis, Crohn’s disease, celiac disease, autoimmune hypothyroidism (Hashimoto’s hypothyroidism, Graves’ disease, atrophic thyroiditis, etc.), rheumatoid arthritis, etc.
Diagnosis
At this point, in the case of a suspected bacterial overgrowth, it may be helpful to have a diagnosis in order to refine the subsequent treatment.
If you choose to have a diagnostic report, I will detail the chronological order and the steps to follow:
Which medical professional to go to first?
The first thing you should do is a medical visit for diagnostic orientation and request for tests. Go to a digestologist who is up to date on the subject of bacterial overgrowth. After a clinical anamnesis, he/she will have the necessary information to guide you in the tests to be performed.
What tests should be performed?
The appropriate test to screen for SIBO is the lactulose or glucose breath test.
The test is non-invasive and consists of blowing through a mouthpiece to measure, at different times over 3-4 hours, the amount of hydrogen and methane in the breath after taking a substrate (10g of lactulose or 75g of glucose).
The results on the amount of gas found are presented in the form of curves like the ones I show you below, where on the horizontal axis are expressed the elapsed time in minutes and on the vertical axis the amount of gas calculated in parts per million (ppm). You can find the two gases in one curve or in two separate curves. Some laboratories also include the collected data in tabular form.
Interpretation of results: Hydrogen and methane are gases produced by the microbiota. Their elevation in the first part of the test (the first 90 minutes or so, it may vary according to the speed of intestinal transit of each person) indicates the presence of microbiota in the small intestine and therefore a positive SIBO. More precisely, bacterial overgrowth should be diagnosed at:
- an elevation of 20ppm or more of hydrogen (H2) with respect to the basal value, or.
- an increase of 10ppm or more in methane (CH4) from baseline.
Limitations of this test: You could get a negative test but have symptoms during its performance, in this case there is controversy on how to proceed, although many professionals choose to treat the symptoms as if the test were positive because it may have limitations, among others:
- Give false negative in the case of people with a rapid intestinal transit, for example those with short bowel syndrome, in these cases the elevation of gases can occur after 90 minutes which is considered physiological (negative test).
- False negative in the case of a SIBO by hydrogen sulfide, since up to now no curves with evaluation of this gas have been performed. Thus, methane and hydrogen curves may not be elevated but there may be symptoms if we are facing this type of overgrowth.
