The relationship between small intestinal bacterial overgrowth (also known as SIBO) and gut symptoms is hotly debated in the academic world. Evidence suggests that small bacterial dysbiosis may be more important than overgrowth when it comes to gut symptoms, and that SIBO can often be present in people eating a healthy diet that have no symptoms.
In a recent paper (reference at the end), 126 patients with gut symptoms were assessed for SIBO, with 52% testing positive. The microbiome of the 126 patients’ small intestine was compared to 38 healthy volunteers that all tested negative for SIBO. The measurement for SIBO was not by breath tests as is currently used in clinical practice, but rather by using a tube to suck out some of the fluid from the small intestine and then growing this and assessing the quantity of bacteria. While this method is great scientifically, this is unlikely to replace general SIBO testing in practice due to cost.
In addition to these comparisons, 16 healthy people (no symptoms) that ate a healthy high-fibre diet were tested for SIBO, with 50% testing positive. These healthy people were then changed over to a low-fibre diet high in refined sugar for seven days. Observations from this dietary change were: lower bacterial diversity that was associated with gut symptoms (seen in 80%); lower faecal butyrate and acetate (anti-inflammatory acids); and increased gut permeability.
Authors concluded that:
1. The presence of excess bacteria in the small bowel did not correlate with gut symptoms such as diarrhoea, bloating, and colonic sensitivity;
2. People with gut symptoms had differences in bacteria compared to healthy controls; these could be explained by being older, using antacids (PPI), recent antibiotic use and previous gut surgery, but not by SIBO;
3. A positive association with dysbiosis (gut bacteria different than the healthy controls) was observed for being older, using antacids (PPI), recent antibiotic use and previous gut surgery;
4. SIBO was not correlated with dysbiosis; in other words, some people with diagnosed SIBO have a normal-type microbiota whereas some people with dysbiosis would not meet the criteria for being diagnosed with SIBO;
5. The presence of SIBO was most strongly associated with recent antibiotic use;
6. 71% of those with symptoms had normal small intestinal microbiota, 29% had dysbiosis;
7. Healthy people can have SIBO – and it doesn’t cause any symptoms but may be a feature of a high fibre diet.
1. Having dysbiosis of the small intestinal microbiota is a greater driving factor of symptoms than have a positive SIBO diagnosis;
2. Efforts should be made to increase fibre and fibre diversity to help combat dysbiotic microbiota, promote beneficial acid production, and lower intestinal permeability;
3. Gut symptoms such as bloating, diarrhoea and faecal urgency – with a positive SIBO breath test – DO NOT necessarily mean that SIBO is the cause of this (as symptoms weren’t associated with SIBO);
4. Use of antibiotics to treat SIBO should be considered only after dietary efforts to identify specific food triggers and diversify the diet have been accomplished;
5. If you are taking an antibiotic, ensure you have a good variety of fibre (plant-based foods) in your diet and consider taking a probiotic while taking the antibiotic and for some time after to fortify your gut bacteria.
If you have been told you have SIBO or suspect you might, please book into clinic with Dr. Bridgette Wilson, who can help you to find the root cause and the appropriate dietary management to achieve symptom control.