The syndrome of intestinal bacterial overgrowth or overgrowth is also known under the name of small intestinal bacterial overgrowth (SIBO) in English. Still unrecognized, it often overlaps or is often associated with irritable bowel syndrome, with which it shares many symptoms. Some research suggests that SIBO is present in 80% of cases where there is irritable bowel syndrome.e.
It is one of the most common causes of malabsorption. We speak of bacterial overgrowth syndrome when the number of bacteria present in the small intestine is greater than 105bacteria / mL. The problem is not with the quality of the bacteria, but rather with having too many normal bacteria in the wrong place. By multiplying in the small intestine, these bacteria, which feed on carbohydrates, produce gases which could cause various symptoms.
The concentration of bacteria in the gut is maintained by various factors such as movement of intestinal contents (peristalsis), stomach acid production and mucus. In individuals with Bacterial Gut Overload Syndrome, some of these factors may be altered which allows gut bacteria to proliferate and leads to malabsorption of ingested nutrients and other symptoms.
The cause of intestinal bacterial overgrowth syndrome is not yet clear.
It could be caused by disorders that decrease or slow down the movement of intestinal contents, reduce the passage of excess bacteria and therefore allow certain bacteria normally present in the intestine to proliferate. The causes of this syndrome could be grouped into 4 categories:
They can occur during long-term treatment with proton pump inhibitors (often prescribed to relieve gastric reflux).
Anomalies and / or anatomical changes in the stomach and / or small intestine
They can be caused by diseases such as diverticulosis or occur after surgery such as gastrectomy.
Bowel movement disorders
They can be caused by different diseases like scleroderma, diabetes mellitus, chronic pancreatitis, hypothyroidism, etc. This is because diabetes is the most common cause of slow bowel movements.
Irritable bowel syndrome and celiac disease are also fairly high prevalence factors for SIBO.
Lack of gastric acid secretion (achlorhydria)
Associated with bowel movement disorders, it can cause bacterial overgrowth, especially in the elderly.
Symptoms of bacterial overgrowth syndrome may include extradigestive symptoms such as chronic fatigue or trouble concentrating, headache, joint pain, eczema, asthma rosacea, depression
Of course, there are digestive symptoms, such as abdominal pain, bloating, gas, belching, nausea, reflux, constipation, diarrhea or steatorrhea (oily diarrhea). This is because excess intestinal bacteria alter the bile salts involved in the digestion of lipids, which leads to malabsorption of fat and can be the cause of steatorrhea, or even anemia.
However, many people with this syndrome are asymptomatic and only show weight loss or nutritional deficiencies. This is because the bacteria present in excess consume the nutrients ingested, in particular carbohydrates and vitamin B12, which can lead to deficiencies in calories, vitamins and minerals.
Currently, the gold standard diagnostic test for bacterial overgrowth syndrome is culture of a sample of intestinal fluid with a bacterial concentration greater than 105bacteria / mL. However, this test has certain limitations. Indeed, this test is invasive since it requires an endoscopy, it is expensive, it carries risks of contamination, it may not detect the syndrome if it is present in a more distant section of the small intestine and the culture intestinal bacteria can be difficult. To overcome these drawbacks, indirect detection methods for the syndrome have been developed.
For example, there are now non-invasive respiratory tests, but these tests are also less sensitive and less specific. Therefore, more research is needed to develop less invasive diagnostic methods for intestinal bacterial overgrowth syndrome.
Medical treatment for bacterial overgrowth syndrome includes antibiotics, such as rifaximin or metronidazole, and dietary modifications. One third of patients are believed to be cured with just one prescription for antibiotics. However, recurrences are still frequent, as the cause of the onset of SIBO must also be addressed. The challenge for gastroenterologists is to deal with the underlying dysfunction, which causes bacteria to overgrow. In some cases, unfortunately, this is almost impossible. However, it is possible to treat with antibiotics more than once, and some drugs can also help speed up small intestine motility. Also, gastroenterologists suggest probiotic cures as well as alow FODMAP diet to help patients regain digestive comfort.
The nutritional approach to bacterial overgrowth syndrome involves modification of the diet. Indeed, adopting a diet low in carbohydrates (the FODMAP diet) and high in fat is generally recommended. This diet may be beneficial in limiting digestive symptoms and malabsorption since gut bacteria primarily consume carbohydrates at the expense of fat. This diet thus makes it possible to limit bacterial growth. Finally,food supplements quality can also be used to prevent or correct nutritional deficiencies in calories, vitamins, minerals, etc.
As for the other causes of malabsorption, the nutritional approach of intestinal bacterial overgrowth syndrome aims to adjust food intake in order to provide a diet that is the most adequate and balanced possible while limiting digestive symptoms and avoiding worsen malabsorption. These adjustments may require the assistance of a dietitian to determine the right food intake for each individual's needs, to define the appropriate foods and to implement personalized dietary strategies.
- Dibaise, J. K. Assessment of malabsorption.” Modern Nutrition in Health and Disease, by A. Catharine Ross, Wolters Kluwer / Lippincott Williams & Wilkins, 2014, pp. 10541057..
- Detail- Swiss Medical Forum (medicalforum.ch)
Article written by:
Marie-Noël Marsan, Nutritionist