What is Small Intestinal Bacterial Overgrowth?

SIBO or Small Intestinal Bacterial Overgrowth, is caused when bacteria that are normally present in the large intestine start to grow in the small intestine. When the wrong kind of bacteria populate the small intestine, it can lead to uncomfortable symptoms such as gas and diarrhoea. The overgrowth of bacteria can also inhibit your ability to digest and absorb nutrients from food, as the bacteria use the nutrients to fuel their own survival.

Typical symptoms of SIBO include [i] [ii]:

• Abdominal pain.
• Abdominal distension.
• Nausea.
• Bloating.
• Indigestion.
• Gas.
• Diarrhoea.
• Constipation.
• Unintentional weight loss.
• Fatigue.

How does SIBO occur?

A collection of chemical and mechanical functions stop the condition of SIBO from occurring in healthy people. In cases of SIBO development, one or more of these functions must fail first, examples of which include: gastric acid, bile, enzymes and immune cells. Low stomach acid (hypochlorhydria), reduces the normal defensive action stomach acid has against unwanted pathogenic (disease-causing) bacteria.

SIBO may also be caused by a failing or impaired movement of food on its journey from the small intestine to the large intestine. If this mechanism is slowed or impaired, this allows more time for the bacteria to grow in the small intestine. Small intestine dysmotility therefore describes the effect of waste being retained for too long in the small intestine before emptying into the large intestine, allowing the small intestine bacteria to continue to multiply. This includes conditions such as gastroparesis, intestinal pseudo-obstruction and hypothyroidism.

Other conditions of the bowel such as small bowel diverticulosis, small bowel obstructions and abdominal adhesions can reduce movement of the gut and provide small spaces for bacteria to accumulate [iii].

Risk factors include advancing age reducing the amount of stomach acid being produced [iv], medical interventions can affect immunity and the structure and function of the digestive system. Conditions increasing risk of SIBO include: diabetes, lupus, coeliac disease, inflammatory bowel diseases, irritable bowel syndrome and liver cirrhosis [v] [vi].

Moreover, use of antibiotics and gastric acid suppressants (such as PPIs) can upset the normal balance of gut flora.

SIBO is diagnosed via a breath test [vii]. The test measures hydrogen and methane levels in the breath to determine the presence of certain types of gas-producing bacteria in your gut. A course of antibiotics is the standard medical treatment for severe bacterial overgrowth [viii].

Dietary and supplement suggestions

In existing SIBO conditions, consumption of certain foods can upset the normal balance of flora. SIBO may be helped by the reduction of some of these foods to help prevent overgrowth by starving the problematic bacteria of their preferred fuel. Examples of food to avoid includes, sugars and sweeteners, fruits and starchy vegetables, dairy products and grains. It is also important to include nutritional support and supplementation for vitamin and mineral deficiencies. In SIBO cases, it is common that malnutrition and vitamin (B12, D, A, and E) as well as minerals (iron, magnesium, zinc and calcium) deficiency may be present [ix]. It is worth sourcing nutritional testing under the guidance of a nutritional therapist to ascertain individual needs.

The importance of nutritional therapy for SIBO

To get cases of SIBO into remission, occasionally a short-term elimination diet is recommended. Some more severe cases may require a stricter approach such as a the elemental diet, to control the infection. The elemental diet is a diet of many supplemental liquid formulas in place of meals, it is designed to reduce the bad gut bacteria by providing nutrients for the body to strengthen the immune system whilst escaping the fuelling of the bacterial infection. These types of diets should only be practiced under the guidance of a qualified nutritional therapy.

A variety of other low-carb diet plans may also be an option to try such as an elimination diet, to identify food triggers [x](9). Elimination diets require certain foods to be eliminated and after a period of time the foods are reintroduced on an experimental basis, to test the body’s reaction. Low carb diets such as the Specific Carbohydrate Diet (SCD) has been shown to reduce SIBO [xi] [xii].

Testing options for SIBO

Gastro Intestinal Test: this is a comprehensive stool analysis test that evaluates all the micro-diversity in your digestive system.

Our Nutritional Therapy team are experienced in working with clients where SIBO is an issue. If you'd like to chat to one of the team please get in touch.