What are the Signs of SIBO I Might be Ignoring?

bloating blog fodmap fodmap diet fodmap recipes gut health ibs sibo

Small Intestine Bacterial Overgrowth (SIBO) is a condition where there is an excessive amount of bacteria in the small intestine, which can cause an imbalance and lead to a range of gastrointestinal symptoms. 

What are the Signs of SIBO?

If food travels slowly in the digestive tract or there is reduced stomach acid, it can create the perfect environment for bacteria to start to overgrow! They begin to feed off the food we eat and produce hydrogen methane gases, which can lead to significant and uncomfortable symptoms. An immediate sense of fullness can be one of the first signs as can abdominal pain, bloating, nausea/vomiting, abnormal stools, smelly flatulence (due to fat malabsorption) and diarrhoea or constipation. SIBO can also cause indigestion and malnutrition which can lead to weight loss. If SIBO goes untreated and is severe, it can lead to vitamin deficiencies as the bacteria consume some of the nutrients you should be getting.

What are the causes of SIBO?
The causes of SIBO are not fully understood, and there are several factors that are believed to contribute to its development.

One of the main factors is a disruption in the normal motility or movement of the small intestine. This can involve anatomic abnormalities (post bowel procedures including resections) or malfunction/weakness in the muscular activity of your digestive system. When digestion is slowed or halted and food is sitting in our digestive tract for a longer period of time, this can allow bacteria to accumulate and grow. This can be caused by conditions such as diabetes, scleroderma, and certain autoimmune disorders.

Low gastric acid secretion can also cause SIBO, as the growth of bacteria in the digestive tract is not suppressed by a low pH. This can occur with the use of histamine type 2 receptor blockers (H2RAs) or proton-pump inhibitors (PPI).

Other risk factors that may contribute to SIBO include:

  • A weakened immune system
  • Viral gastroenteritis
  • Coeliac disease
  • Inflammatory bowel disease
  • Irritable bowel syndrome
  • Parkinson’s disease
  • Hypothyroidism
  • Poor diet
  • Low stomach acid levels
  • High alcohol intake
  • Medications, particularly those that impact gastric motility

Testing for SIBO

Diagnosis of SIBO can be challenging, as symptoms can overlap with other digestive conditions including IBS. Some tests that are used include:

  1. Aspirate and fluid culture from the small intestine
    This is the gold standard method that examines a sample from the small intestine to estimate the presence of a high number of bacteria. Doctors perform an endoscopy to the small intestine where a sample of intestinal fluid is withdrawn and then tested in a laboratory for the growth of bacteria. It is quite invasive and therefore rarely used in clinical practice.
  2. Hydrogen breath testing
    This is the more common method where the patient consumes a special drink containing a sugar that is fermented by bacteria in the small intestine. The breath is then analysed for levels of hydrogen and methane, which can indicate the presence of SIBO. Although this method is non-invasive, it lacks specificity and sensitivity in results.
  3. Other tests include indications from stool analysis and blood work to check for markers of inflammation

It is important to see a doctor or gastroenterologist for proper evaluation before self-diagnosing to exclude other possible causes and ensure commencement of the correct treatment.

How is SIBO treated?

Antibiotics are the first line of treatment for SIBO in eliminating the bacterial overgrowth in the small intestine. The most common antibiotic used is Rifaximin, as well as Ciprofloxacin and Metronidazole.
However, antibiotics can also disrupt the natural balance of good and bad microbes in the gut, so adjunct therapies, including diet and a probiotic can prevent further gastrointestinal upset and help in controlling SIBO.

Probiotic use has also been suggested to be an effective treatment in not only managing SIBO but also in reducing gut disturbances associated with antibiotic use.
Saccharomyces Boulardii and Lactobacillus Rhamnosus GG are two probiotic strains that been studied specifically for their effectiveness when taken alongside antibiotics. Other probiotic strains that have been suggested for SIBO included Bifidobacterium (bifidum; lactis; and longum); Bacillus Coagulan; and Lactobacilli (casei; acidophilus; and plantarum).
One meta-analysis and systematic review concluded that probiotics assist in reducing SIBO, hydrogen gas concentration and relieving abdominal pain.

A low FODMAP diet may be recommended following antibiotic treatment to prevent reoccurrence and manage symptoms. This is based on two ideas- one- that reducing fermentable carbohydrates in the diet “starves” the bad gut bacteria; and two- that the diet is effective in helping to manage the gastrointestinal symptoms of SIBO including bloating and gas.
Other dietary therapies proposed include the elemental diet, the Gut and Psychology Syndrome (GAPS) diet and the Specific Carbohydrates Diet (SCD).
However, scientific evidence for the effectiveness of these diets for SIBO are limited and do not provide sufficient evidence to fully support diet as an independent viable treatment.

A healthy, balanced diet, low in refined sugars and carbohydrates is a more simple diet that may be recommended to help balance the microbiome and promote growth of the good gut bacteria.
A diet high in prebiotics and probiotics will help to support and maintain the gut microbiome back to a balanced state. This includes consuming probiotics as above in supplement form or also through foods including yoghurt, Yakult and kefir. Prebiotics can also be found in supplement form or in a diet varied in wholegrains, legumes, nuts, seeds, fruits and vegetables.

SIBO can sometimes cause nutritional deficiencies due to digestion and absorption issues. Therefore, seeing a dietitian will ensure all your nutritional needs are being met whilst following an appropriate diet.

How do I improve my stomach acid levels?

Low stomach acid may be a contributor to SIBO as the acidity is responsible for killing harmful bacteria, regulating the balance of bacteria and neutralising enzymes.

One simple but effective way to improve stomach acidity is by thoroughly chewing your food. This not only makes digestion of food easier for our body, but also stimulates excretion of digestive enzymes in the mouth and stomach.

Introduction or addition of some foods in the diet can naturally help to improve stomach acidity levels.
Probiotic-rich, fermented foods such as kefir, sauerkraut and kimchi can help to increase the good bacteria in the gut, which can aid in digestion and improve stomach acid levels. Certain spices and herbs can also help to stimulate stomach acid production, including ginger, turmeric, and cinnamon, which can be incorporated into meals such as curries or consumed in more simpler forms such as tea or supplements.
Additionally, avoiding trigger foods that may exacerbate acid levels, such as spicy or fried foods, caffeine, and alcohol, can help improve stomach acid levels.

How do I improve my gut motility?
Poor gut motility is another major cause of SIBO as slowly digested food sitting in the digestive tract can encourage bacteria to accumulate and grow. Poor motility can also impact on our bowel movements and result in constipation, which can allow bacteria in the large intestine to move up into the small intestine and populate, also leading to SIBO.

Our Migrating Motor Complex (MMC) is a system of electrical waves that migrates digestion from the stomach and through the small intestine. It is particularly active between meals for a duration of 80-220 minutes, with its main goal to move undigested food particles and bacteria from the small intestine. Poor or incomplete movement of the MMC can result in bacteria building up in the small intestine, leading to SIBO.
Specific strategies that can improve our MMC include having smaller meals and leaving enough time between eating periods to allow the MMC to do its thing.
Some other strategies to promote movement of the digestive system include humming and singing which stimulates the vagus nerve. The vagus nerve is activated when we are in our rested state and regulates our digestive organs including production of stomach acids, stomach churning and stimulation of the small and large intestine to push food and waste through the digestive tract.
Slow, deep breathing not only helps us to relax and de-stress, but it another way to activate the vagus nerve and helps us enter “rest and digest” to get digestion moving. Meditation and other activities that help us to slow down such as yoga benefit in the same way.

Exercise can also help to get the digestive system moving. Low-medium intensity exercise on a daily basis can promote regular bowel movements and aid digestion.

The bottom line
SIBO more commonly occurs from an underlying cause. Therefore, most medical and dietary treatments for SIBO are more immediate and may not be effective for eliminating and reducing SIBO in the long term. A dietitian can help with planning appropriate dietary management and reducing your risk of nutrient deficiencies and malnutrition. Therefore, it is important to assess the cause/s of SIBO with a doctor or gastroenterologist for specific management of the root problem.


If you suspect you could have SIBO or if you are suffering from gut symptoms and need help, book a time to speak with one of our expert gut health dietitians here.

Stay connected with news and updates!

Join our Free Monthly Newsletter to receive the latest news and updates from our team.