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The Small Intestine

The small intestine accounts for over 56% of our intestinal tract.

The small intestine is a key area of our digestive tract , in fact, the small intestine has as much relevance to hypothyroidism, celiac disease, and IBS. Although most of us tend to be deficient in exposure to environmental bacteria because of our overly hygienic environment, we tend to have overgrowths of bacteria in the small intestine. SIBO (small intestine bacterial overgrowth) is a term we will be talking about later. Approaches that feed bacteria may not work well for conditions like the ones mentioned above. If we have a bacterial overgrowth, feeding bacteria can make it worse.

Let's cover some basics first and then we can talk about its bacteria.

The small intestine is responsible for 90% of caloric absorption

The colon or large intestine only represents 20%, so 90% of the food we eat is absorbed through the small intestine, this makes the small intestine a BIG DEAL! The small intestine has a profound impact on our immune system, the largest mass of immune cells in our body are seen in the small intestine. This is why small intestinal health is so important.

The small intestine has a thin, protective mucous membrane and is much more prone to damage, which can result in leaky gut. This damage underlies many immune and autoimmune conditions, food reactivity, and the malabsorption of nutrients. The small intestine harbors a relatively small number of bacteria compared to the large intestine. This is important because it explains why the large intestines have different needs.

Current recommendations seem to favor the large intestine - fee your gut bacteria by eating lots of fiber, carbs, and prebiotics. However following this advice can create problems for the small intestine. I hope by now you realise that the small intestine is the most important section of our gut and the entire digestive tract.

Overgrowth of bacteria in the small intestine is probably what is causing gas, bloating, diarrhea, constipation, high blood sugar, high cholesterol and weight gain. Because the small intestine is so important when it becomes imbalanced it can cause a wide range of negative health effects.

How do bacteria and the small intestine tie in with celiac disease and hypothyroidism? Many people with these diseases have too much bacteria in their small intestine and thus do better with approaches that reduce or rebalance bacteria levels.

Celiac Disease And The Small Intestine

Celiac disease is the most severe form of gluten intolerance, it causes inflammation and autoimmune damage to the intestines. Several human studies have shown that there is increased bacterial count and diversity in the small intestine of those with celiac disease, essentially, they have bacterial overgrowth. An increased diversity in the healthy bacterial species of bifidobacteria has been shown in children with celiac disease when compared to healthy controls. This same increased diversity has been shown in adults with celiac disease. Although not all studies agree on this, there is enough evidence to suggest bacterial overgrowth is an issue for many with celiac disease. It is important to point out that celiac disease predominantly affects the small intestine, not the large.

Short chain fatty acids tends to be high in the stool of people who suffer from celiac disease. Short chain fatty acids in the appropriate levels can be beneficial, high levels have been documented in those with celiac disease and in those who are obese. In summary the reason those with celiac disease have high levels of short chain fatty acids is likely because of bacterial overgrowth. Too much bacteria equals too many short chain fatty acids. The good news is that levels of short chain fatty acids appear to normalize after treatment with a gluten free diet.

It is possible that those with celiac disease aren't absorbing nutrients, thus making available more substrate for bacterial feeding, this feeding causing bacterial overgrowth and subsequent elevated production of short chain fatty acids. People with celiac disease may have impaired motility, which causes bacterial overgrowth. Motility is the ability of our intestines to keep food moving through them at an appropriate pace. Inflammation impairs this motility. When food doesn't move through our intestines quickly enough it can cause bacterial overgrowth.

It has been shown that inflammation causes an unfavorable balance of bacteria in the gut. Why? Because inflammation is a major factor in the health of our internal environment. Inflammation can kill good bacteria and encourage growth of bad bacteria.

Eating To Reduce Inflammation Is More Important Than Eating To Feed Bacteria

An inflamed environment is unhealthy, therefore an inflamed environment equals unhealthy bacteria. The bottom line is that those with celiac disease might need an approach that reduces excessive bacteria in the small intestine. Accordingly, it has been documented that SIBO is a common reason why people's symptoms don't improve on a gluten free diet. More importantly, after treating their SIBO properly most people become symptom free. SIBO can be assessed with a simple breath test. However, you don't need to do this test now, even if this sounds like you. We will look into the steps in later blogs that will address SIBO, as well as other gut imbalances.


How does the small intestine connect to IBS? SIBO is known to cause gas, bloating, constipation, diarrhea, and abdominal pain, in other words, the symptoms of IBS. Current treatment guidelines state those with SIBO shouldn't feed their gut bacteria, or at least do so very cautiously. There are herbs that have been shown effective in treating SIBO and IBS, we will look into these in later blogs

The Far Reaching Effects Of The Gut

Small intestine bacterial overgrowth, can cause or contribute to problems in other parts of the body. These problems include but are not limited to brain fog, depression, fatigue, skin conditions, joint pain, hypothyroidism, and other autoimmune conditions, It is KEY for us to achieve gut health because there is a good chance a gut imbalance underlies current symptoms.

We are beginning to develop a context for understanding our gut and our gut microbiota. The small intestine is a crucial aspect of our digestive tract that holds much potential for improving overall health.

In the next blog we are going to look at different cultures and understand why not all guts are the same.

The above information is taken from the Healthy Gut Healthy You Book, by Dr. Michael Ruscio

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