At this point in 2022, we've all heard how important the intestinal microbiome is. The health of our microbiome has an impact on our health, ranging from our cardiovascular function, immune function, mental health, metabolic function, and more. But it's not just about having the right "types" of bacteria, but also how much of those bacteria are present.
SIBO (Small Intestinal Bacterial Overgrowth) is a condition in which there are too many bacteria in the small intestine, resulting in a cluster of symptoms. This may be an overgrowth of what is already in the small intestine, or alternatively, bacteria that make their way from the large intestine to the small intestine, causing an increase in numbers.
5 hints that you might have SIBO
1. Your symptoms get better with antibiotic use
Different antibiotics have a different range of bacteria they will kill. The most commonly prescribed antibiotics are "broad-spectrum," meaning they kill a wide variety of bacteria including those commonly found in the GI tract. If you notice that your GI symptoms improve with a round of antibiotics, it just may be that they are knocking back some of that overgrowth leading to a reduction in symptoms.
2. Your symptoms get worse with probiotics containing prebiotics
Probiotics are often touted as the catch-all treatment for GI concerns. In SIBO, they might just be making matters worse. Many brands of probiotics contain prebiotics as well. Prebiotics are fibers found in foods (i.e., inulin, resistant starches) and help promote the growth of bacteria. Prebiotics are perfect if the goal is to rebuild healthy bacteria, but they can make the symptoms of SIBO significantly worse by further increasing the overgrowth numbers.
3. You experience bloating that worsens throughout the day and is alleviated first thing in the morning
Gas and bloating are hallmark symptoms of SIBO. This is mainly due to the fermentation of carbohydrates from the overgrown bacteria, producing large amounts of gas (typically hydrogen). When we are actively eating throughout the day, the fermentable carbohydrates we are eating are being actively broken down by the bacteria, resulting in gas production and increased bloating. When we are not eating throughout the night, these symptoms are alleviated, and we feel better when we first wake up.
4. You've been diagnosed with IBS or struggle with chronic diarrhea/constipation
Not all people who have IBS have SIBO, but if you've been diagnosed with IBS and have not been able to get the symptoms under control, it might be something to look into. In a review of fifty studies looking at the prevalence of SIBO among patients with IBS, more than one-third of patients diagnosed with IBS were also diagnosed with SIBO.
5. In addition to gut symptoms, you also have elevated anxiety and/or depression
The gut-brain axis has become well established in medicine. The microbiome directly influences mental health, and SIBO is no exception. SIBO has been highly correlated to increases in anxiety and depression. The exact mechanism isn't clear; however, an overgrowth of bacteria can result in decreased nutrient absorption and increased production of toxic metabolites, which likely are contributing factors to the mood changes seen.
Risk factors for developing SIBO
Identifying SIBO is important, but equally as important is understanding why it developed in the first place so that we can address it and prevent future recurrences. The most common underlying reason for SIBO is related to "intestinal motility" (how good is your gut at keeping things moving), altered gut microbiome, and damage/inflammation of the intestinal tract. Without the body being able to move waste effectively and consistently through the gut, the more likely the chance of bacterial overgrowth.
Some risk factors for SIBO include:
- Chronic use of PPIs or antacids
- Pancreatic insufficiency or chronic pancreatitis
- Chronic opiate use
- History of abdominal surgery
- Unmanaged hypothyroidism
- IBD (Crohn's and Ulcerative Colitis)
- Celiac disease
How to test for SIBO
SIBO is typically tested via a hydrogen breath test. It consists of a prep diet that removes foods known to feed the bacteria and worsen SIBO symptoms. The following day the breath test measures how much methane and hydrogen gas is produced by the bacteria after consuming a sugary drink solution. The gasses are measured over 2-3 hours and are compared to a baseline.
Because of how much overlap there is between SIBO and other GI conditions, it's always best to test to make sure you know what you're treating so there's no risk of unnecessary treatments or misdiagnosis. If you think you might be suffering from SIBO, it's best to schedule an appointment with a naturopathic/integrative medical provider to get the right assessment, testing, and treatment.
- Bull MJ, Plummer NT. Part 1: The Human Gut Microbiome in Health and Disease. Integr Med (Encinitas). 2014;13(6):17-22.
- Chen B, Kim JJ, Zhang Y, Du L, Dai N. Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis. J Gastroenterol. 2018;53(7):807-818. doi:10.1007/s00535-018-1476-9
- Takakura W, Pimentel M. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome - An Update. Front Psychiatry. 2020;11:664. Published 2020 Jul 10. doi:10.3389/fpsyt.2020.00664
- Bested AC, Logan AC, Selhub EM. Intestinal microbiota, probiotics and mental health: from Metchnikoff to modern advances: Part II - contemporary contextual research. Gut Pathog. 2013;5(1):3. Published 2013 Mar 14. doi:10.1186/1757-4749-5-3
- Achufusi TGO, Sharma A, Zamora EA, Manocha D. Small Intestinal Bacterial Overgrowth: Comprehensive Review of Diagnosis, Prevention, and Treatment Methods. Cureus. 2020;12(6):e8860. Published 2020 Jun 27. doi:10.7759/cureus.8860
- Sachdev AH, Pimentel M. Gastrointestinal bacterial overgrowth: pathogenesis and clinical significance. Ther Adv Chronic Dis. 2013;4(5):223-231. doi:10.1177/2040622313496126