Small Intestinal Bacterial Overgrowth (or SIBO) is a chronic bacterial (and/or yeast) infection of the small intestine, characterized by excessive number and/or abnormal type of bacteria (and yeast) growing in a part of the gastrointestinal tract that normal contains relatively few microorganisms. These bacteria can cause a variety of problems by interfering with digestion and absorption of nutrients and by damaging the lining of the gut, causing a “leaky gut” (I addressed the many health problems that can arise from a leaky gut in this post).
The most common symptoms of bacterial overgrowth include abdominal pain, nausea, bloating, gas, belching, flatulence, chronic diarrhea, and chronic constipation. These symptoms are due to the large volume of bacteria the digestive tract (alive and dead, as they read the end of their lifecycle) and the large amount of gas and metabolic waste that they produce. Many more symptoms of SIBO are a direct effect of nutrient malabsorption. This arises either from the bacteria metabolizing those nutrients before we can absorb them or by the bacteria causing enough inflammation in the lining of the gut that it the gut can’t work properly anymore. For example, the bacteria preferentially consume iron and vitamin B12, causing anemia. The bacteria decrease fat absorption by deconjugating bile leading to deficiencies of vitamins A & D and causing steatorrhea (fatty stools). As the gut lining becomes increasingly inflamed and leaky, larger and not fully digested food particles enter the body, causing an immune reaction which leads to food allergies and food sensitivities. Bacteria themselves can enter the blood stream causing systemic inflammation and immune reactions that can lead to autoantibody formation and autoimmune diseases (for a comprehensive review article see the footnote).
SIBO was only described in the late 1990s and is still grossly underdiagnosed. This is partly because many patients don’t seek medical attention for their SIBO symptoms, because many doctors aren’t aware of its prevalence and don’t consider it in their differential diagnostics, and because the tests for SIBO still have fairly high false negative rates (where you have the disease but the test says you don’t). As SIBO becomes more recognized, it is also becoming inextricably linked with many other diseases. Many physicians and scientists now believe that Irritable Bowel Syndrome (the cause of which has never been properly defined) is actually a group of symptoms caused by SIBO (see the book The New IBS Solution). SIBO is also often associated with Crohn’s disease, Celiac disease, short bowel disease, various liver diseases, fibromyalgia, some autoimmune diseases (such as scleroderma, diabetes, lymphoma, and chronic lymphocytic leukemia and the aforementioned Crohn’s disease and Celiac Disease) and even rosacea (for a fantastic summary of confirmed related diseases, see http://www.siboinfo.com/associated-diseases.html). Whether SIBO is a causal factor or a symptom of these diseases remains to be determined. Given how new all of this science is (and how prevalent SIBO actually is!), I suspect that over the next few years many more health conditions will linked with SIBO.
How do you know if you have SIBO? If you have digestive symptoms, especially if they persist after adopting a strict paleo diet, SIBO is a possibility. You can opt to get tested (there are several different test options which can be ordered by your primary care physician), however know that the current testing methods are not 100% reliable. One of the easiest ways to determine whether you have SIBO is to see if diet modifications aimed at treating it make you feel better.
How can you fix SIBO? There are two diets (very similar to each other) that have been developed with the intention of starving the bacteria in the small intestine and healing the damaged lining of the gut. These are the GAPS (Gut and Psychology Syndrome) diet(see Gut and Psychology Syndrome) and the SCD (SpecificCarbohydrate Diet) diet (see Breaking the Vicious Cycle). The general approach to these diets is to eliminate any dietary sugars that are not monosaccharides. Monosaccharides are simple sugars like glucose and fructose and are the most easily absorbed in the digestive tract. More complex sugar molecules like sucrose (i.e., table sugar which is a disaccharide) and starches have to be broken down into monosaccharides before they can be absorbed. This means that the sugar takes longer to be digested, which means it travels farther down the digestive tract before being completely absorbed, which means that some of it reaches the abnormal bacteria growing in the small intestine and provides a food source for them. These diets also focus on consuming healing foods such as bone broth, conjugated linoleic acid found in the fats from grass-fed animals, and coconut oil. I recommend combining one of these diets with a paleo diet for the most rapid and effective reversal of SIBO.
A standard paleo diet is typically not enough to treat and reverse SIBO. Attention also needs to be paid to the amount and types of carbohydrates being consumed. I recommend following a paleo diet with modifications disallowing starchy vegetables and high sugar foods as per the SCD and GAPS diets (see my post Fruits and Starchy Vegetables with SmallIntestinal Bacterial Overgrowth). Many people may find taking Apple Cider Vinegar before meals (as outlined in TheStomach Acid Connection) is helpful. For more severe cases digestive supplements may be beneficial (I am not familiar enough with these to recommend a particular brand, type or dose. Recommendations can be found in The Paleo Solution, It Starts With Food, and this post from Chris Kresser. If you need personalized recommendations, I suggest contacting Diane Sanfilippo at www.balancedbites.com). You may also find some good information in my posts Repairing the Gut and What Should You Eat to Heal a Leaky Gut? I also want to mention that stress management is very important (see my post How Mood and Gut Health Are Linked). Homemade bone broth and a source of Vitamin D(sunshine, liver, supplement) are particularly important to promote healing. A source of diverse probiotics (from fermented foods like Sauerkraut,coconut milk kefir, or Kombucha and/or from a high quality supplement) help to restore normal gut microflora (it’s better to keep the dose of these beneficial bacteria on the low side, at least at first, since they can add to the high volume of bacteria and increase symptoms if you’re too aggressive). In extreme cases, a doctor may recommend a course of potent antibiotics followed by a gut-healing protocol (exactly what is outlined above) and probiotics. For those with symptoms indicating the early phases of autoimmune conditions (see my post You May Have an Autoimmune Disease But Don’t Know It), following the Autoimmune Protocol for the first 1-3 months may be very beneficial.
Correcting SIBO can take up to 2 years. However, you should see improvement in your symptoms fairly quickly with gradual and continuous improvement (if you don’t, it’s worthwhile considering a FODMAP sensitivity as a confounding factor, which I will be discussing in my an upcoming post). Stress, poor sleep, infections and poor diet choices can all create setbacks. It is always difficult to commit to more restrictive forms of a paleo diet (which can be tough enough as it is!). I have what I believe is a mild case of SIBO. Because I follow the Autoimmune Protocol, I rarely have issues now. However if I slip and eat a high carbohydrate food, I fairly rapidly suffer intense bloating followed by days of gas pains and constipation. It’s not fun to follow such a restrictive diet, but is it worth it!
Bures J. et al. Small intestinal bacterial overgrowth syndrome. World J Gastroenterol. 2010 June 28; 16(24): 2978–2990.