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SIBO (Small Intestine Bacterial Overgrowth)

When the gut bacteria get out of hand

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First published: 11.Oct.2024

Overview

Though papers have mentioned this condition since the early 1970s, using the name SIBO (Small Intestine Bacterial Overgrowth) to describe it, the actual prevalence and causes are still being studied.
Improved testing kits have led to a sharp increase in its diagnosis, but other than antibiotics, no science proven diets have been shown to be effective for its long-term treatment. This article will describe the condition, its causes, symptoms, diagnosis, and treatment. As well as risk factors and its link with celiac disease.

In this Article (Index)

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Introduction

What is SIBO?

drawing of a bloated frowning intestine with different microbes going towards it along arrows
SIBO: far to many microbes in the small intestine

Small Intestine Bacterial Overgrowth or SIBO is an excessive quantity of bacteria in the small intestine. Instead of the normal level of less than 1,000 microbes per milliliter (1 milliliter or ml is roughly equivalent to 1⁄4 the volume of a regular dice), the bacteria can excede the 100,000 - 1,000,000 organisms ⁄ ml levels.

This condition may cause intestinal symptoms ranging from bloating, abdominal pain and chronic diarrhea, to malabsorption of nutrients and this in turn provokes weight loss, vitamin deficiency, and osteoporosis.

Normally the initial section of the small intestine is influenced by the stomach acid, bile, and pancreatic secretions that keep the bacterial population low, but when these fail, bacteria grow out of control.

However, an overabundance of bacteria may not provoke SIBO. The disease only becomes apparent when the bacteria colonizing the area cause inflammation.
These bacteria come from the colonic area, produce chemicals called enterotoxins that can damage the cells that line the small intestine provoking SIBO symptoms. (5)

All you need to know about SIBO

Prevalence

Its prevalence is mostly unknown. But, it is found more often among women and the elderly.
Most authors report rates between 2.5 and 22% prevalence in the general population.
The presence of SIBO was detected in 1 out of three patients with gastroenterological complaints; it is more frequently detected in patients with diabetes mellitus, celiac disease and hypothyroidism compared to control groups without those conditions. (1)

Obese individuals have a risk for SIBO that is 3 times higher than non-obese people, and affects up to 41% of obese people. (2)
SIBO was more frequent in patients who consumed a moderate amount of alcohol than in abstainers (58% vs 39%). (1)

Causes

Roughly 80 to 90% of SIBO cases are caused by Irritable Bowel Syndrome (IBS), chronic pancreatitis, and intestinal motility disorders. Sometimes SIBO may have more than one cause. (5)

Symptoms

SIBO expresses itself with a combination of symptoms: abdominal pain, flatulence, bloating, chronic diarrhea, steatorrhea (excessive fat in your stool, producing loose, oily, foul smelling bulky feces). People suffering from alterations in their gut due to surgery, diverticulosis, IBS, Crohn's disease, etc. may suffer from Blind Loop Syndrome and parts of the small intestine don't move normally leading to bacterial overgrowth.

The damage to the intestinal lining and lower intestinal motility lead to malabsorption of nutrients provoking vitamin deficiencies, in particular Vitamin B12, Vitamin D and iron. Malabsorption leads to unwanted weight loss, weakness, and cramps.

Diagnosis

A breath test is used to validate the diagnosis. It is cheap, fast and noninvasive. Bacteria produce either hydrogen or methane when metabolizing the carbohydrates in food; human cells don't, instead they produce carbon dioxide. Hydrogen and metane is absorbed by the body and then eliminated in the subject's breath. Excessive gas amounts means excessive bacteria and therefore SIBO.

Treatment

Untreated SIBO could lead to intestinal failure.
Your healthcare provider will initially use antibiotics to eliminate the bacteria. Metronidazole, ciprofloxacin, tetracycline, amoxicillin-clavulanate, neomycin, and rifaximin are antibiotics used in the treatment, which will last two weeks.
Vitamin and mineral deficiency will be treated with Supplements. (5)

Diet for SIBO

Diets may not be effective

Diet is also used to treat SIBO. But, the literature doesn't show any conclusive evidence supporting certain types of diets.

The use of probiotics or statins have not shown any proven effects. You would expect probiotics to promote bacterial growth so it wouldn't be effective in treating SIBO.

The "Elemental Diets" used to treat SIBO are based on the notion that depriving the bacteria from the fermentable products they live off will eliminate them by starvation.
These diets eliminate fermentable foods like sugar alcohols, fermentable sweeteners like sucralose, carbohydrates, and fiber. You can find them on the internet but they lack scientific backing. See this example of a homemade diet.

Neither has the FODMAP diet (low Fermentable Oligo, Di, and Monosaccharide diet) been proven effective to treat SIBO, it may even worsen the symptoms. (7)

There isn't any evidence supporting the use of a gluten-free diet to treat SIBO. (8)

Restrictive diets have a low nutritional value and this is negative when considering the nutrient deficiency caused by SIBO. These diets shouldn't be followed for more than a few weeks.

However, there is proof that diet influences the gut microbiome and comparisons between the general population and patients with intestinal diseases show that a diet rich in whole foods, plant foods, healthy oils and fruits with antioxidants can prevent intestinal inflammation and increase the diversity of the intestinal microbiota, improving gut health. (2)

Recurrence

Around 45% of patients will have recurrent SIBO, especially the elderly or those using proton pump inhibitors, like Omeprazole, that reduce the amount of stomach acid. It is treated with antibiotics.

SIBO and Celiac Disease

Small intestinal bacterial overgrowth (SIBO) and celiac disease (CD) have similar symptoms; and research has hinted at a link between both conditions. Further up, we mentioned that SIBO is more prevalent in patients with celiac disease than in non-celiac control groups. (1),(3).

It is possible that the alterations provoked by CD in the defenses of the small intestine may promote the growth of bacteria and that the sudden shift in the diet, removing gluten to treat CD alters microbial diversity and population. Both factors could lead to SIBO in susceptible individuals. (4).

Increase in the rate of SIBO diagnosis

The number of papers covering SIBO has grown almost exponentially over the past two decades. A similar trend has been observed in the Google searches for the term SIBO, as you can see in the following figure.

graph showing increase in Google serches of the term SIBO
SIBO, a growing trend in Google searches

The availability of breath tests has led to an increased detection of SIBO cases, however there is some skepticism regarding false positives and the specific link between these tests and SIBO. (6)

It should be pointed out that "more than one-third of healthy adult subjects are predominantly methane producers" and this gas is produced by a variety of microorganisms known as methanogens that are not bacteria but Archaea. Furthermore, breath tests also have limitations: the sensitivity and specificity are poor. (8)

Closing Comments

SIBO, is a treatable condition, easily diagnosed with a simple, cheap and non-invasive test. It causes discomfort and entails risks if untreated.
However, fad diets found on the internet don't seem to have scientifc backing as an effective treatment for it.
However, a healthy diet with whole ingredients, "good" oils, antioxidants and keeping lean apparently improve gut health and reduce inflammation.

References and Further Reading

(1) Efremova I, Maslennikov R, Poluektova E, Vasilieva E, Zharikov Y, Suslov A, Letyagina Y, Kozlov E, Levshina A, Ivashkin V. (2023). Epidemiology of small intestinal bacterial overgrowth. World J Gastroenterol. 2023 Jun 14;29(22):3400-3421. doi: 10.3748/wjg.v29.i22.3400. PMID: 37389240

(2) Souza C, Rocha R, Cotrim HP.. (2022). Diet and intestinal bacterial overgrowth: Is there evidence?. World J Clin Cases. 2022 May 26;10(15):4713-4716. doi: 10.12998/wjcc.v10.i15.4713. PMID: 35801041

(3) Shah A, Thite P, Hansen T, Kendall BJ, Sanders DS, Morrison M, Jones MP, Holtmann G. (2022), Links between celiac disease and small intestinal bacterial overgrowth: A systematic review and meta-analysis. J Gastroenterol Hepatol. 2022 Oct;37(10):1844-1852. doi: 10.1111/jgh.15920. Epub 2022 Jul 1. PMID: 35734803.

(4) Charlesworth, R. P. G., & Winter, G. (2020), Small intestinal bacterial overgrowth and Celiac disease – coincidence or causation?. Expert Review of Gastroenterology & Hepatology, 14(5), 305–306. https://doi.org/10.1080/17474124.2020.1757428

(5) Sufian J. Sorathia; Venu Chippa; John M. Rivas. (2023). Small Intestinal Bacterial Overgrowth. NIH books. Last Update: April 17, 2023.

(6) Daniel Bushyhead, Eamonn M.M. Quigley. (2022). Small Intestinal Bacterial Overgrowth—Pathophysiology and Its Implications for Definition and Management. Gastroenterology, Vol 163:3 pp593-607, ISSN 0016-5085,https://doi.org/10.1053/j.gastro.2022.04.002

(7) Wielgosz-Grochowska JP, Domanski N, Drywien ME. (2022). Efficacy of an Irritable Bowel Syndrome Diet in the Treatment of Small Intestinal Bacterial Overgrowth: A Narrative Review. Nutrients. 2022 Aug 17;14(16):3382. doi: 10.3390/nu14163382. PMID: 36014888

(8) Rej, Anupam et al. (2022). Evidence-Based and Emerging Diet Recommendations for Small Bowel Disorders. The American Journal of Gastroenterology 117(6):p 958-964, June 2022. | DOI: 10.14309/ajg.0000000000001764

About this Article

SIBO (Small Intestine Bacterial Overgrowth), A. Whittall

©2024 Fit-and-Well.com, 01 Oct. 2024. Update scheduled for 01 Oct. 2027. https://www.fit-and-well.com/health/SIBO.html

Tags: SIBO, gluten, celiac disease, Chron's disease, diets

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