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Is SIBO (Small Intestinal Bacterial Overgrowth) Causing Your IBS?

Updated: Mar 9, 2023

In my last blog post, Looking Beyond an IBS Diagnosis, I discussed what having IBS (Irritable Bowel Syndrome) really means, and why it's important to look beyond this diagnosis, because we now know that there are treatable conditions responsible for IBS symptoms. These are referred to the 'root causes' of IBS, and over the next series of blog posts, I will discuss the the most common IBS root causes I see in my 1:1 clients, and those who complete my IBS Protocol.

This applies to you even if you don't have an official IBS diagnosis. If you have problems with bloating, gas, diarrhea, constipation, reflux, nausea, undigested food in your poop, or autoimmunity, keep reading!

What is SIBO?

SIBO stands for Small Intestinal Bacterial Overgrowth and is defined as an increased number of bacteria in the small intestine.

What is unique about SIBO is that these bacteria move to where they don’t belong and colonise the small intestine, a region that should contain very limited numbers of bacteria.

Because these bacteria are supposed to be in the large intestine, they are mostly species that ferment carbohydrates and the byproduct is either hydrogen or methane gas both of which will result in abdominal bloating. But just like IBS, SIBO sufferers are usually divided into one of three different categories:

Hydrogen SIBO - mostly associated with diarrhea, but sometimes alternating constipating and diarrhea.

Methane SIBO - associated with constipation.

Hydrogen Sulfide SIBO - associated with rotten egg smelling gas.

From this graphic we can see that the stomach contains the least amount of bacteria and this is because it is a highly acidic condition. And then the small intestine has a little more bacteria but in comparison to the large intestines it is virtually barren. So what we see in SIBO is bacteria moves from the large intestines to the small intestine where it doesn't belong. Remember these are species that ferment carbohydrates or feed on carbohydrates creating gas as a byproduct which can result in the types of symptoms we see an IBS, like bloating indigestion gas and irritable bowels.

This is really the reason why we see such success with a low FODMAP diet when it comes to IBS because FODMAPs are fermentable carbohydrates and this is the bacteria's main food source. So by removing these foods the bacteria no longer has anything to feed on and therefore no longer produces gas. But the problem with this is that you end up starving your good guys at the same time, and when you have low levels of beneficial gut bacteria this can cause problems in itself. This is another reason why finding your root is so important so that you don't have to remain on a restrictive diet in the long-term.

Prevalence of SIBO in IBS patients

SIBO is actually a subset of IBS. Not all IBS is SIBO, but The prevalence of IBS is about 10%, so that's about one out of 10 people will have some digestive disorder that actually is IBS.

Estimation is that SIBO is about 60 to 80% of all worldwide cases of IBS, so that's a huge number, and means it's possible that we are looking at about 500 million SIBO cases worldwide, and of course the vast majority doesn't know that they have SIBO. In the past five years, every time I check PubMed, which is a research database, there's just hundreds and hundreds more research studies that are coming out, which is really exciting for you, the SIBO sufferer, to understand this condition more and successfully treat it.

Common SIBO Symptoms

So, what kind of symptoms does SIBO cause?

Here's the most common SIBO symptoms:

  • Bloating

  • Cramping and abdominal pain

  • Constipation and/or diarrhea 

  • Excess gas/flatulence/belching

  • Reflux

  • Fat malabsorption (sticky, oily poo)

  • Leaky gut symptoms - rashes, skin problems, allergies etc

  • Nausea

As you can see they all overlap with IBS symptoms but there is one key symptom that generally give SIBO away and that's bloating. Now you won't necessarily see all these symptoms in someone with SIBO, but bloating almost always occurs because in SIBO we know gas production is a problem and excess gas causes bloating. And this bloating can be really obvious where you are getting bloating quite soon after eating. But in some people it's harder to tell because they feel bloated most of the time. So this is the classic SIBO symptom but really SIBO and compasses all sorts of symptoms because IBS is not just bloating. It's also constipation and diarrhea which could be alternating and abdominal pain and this can be due to the gas and by products produced by the bacteria. SIBO can cause a lot of burping and flatulence as well as nausea and acid reflux. It can cause all sorts of leaky gut symptoms like rashes and food reactions and also malabsorption of fat which can present an oily sticky poos. And beyond obvious gut symptoms in SIBO we often see systemic symptoms like fatigue headaches joint pain and insomnia.

Types of SIBO

As I mentioned before, just like with IBS, we usually see three distinct types of SIBO.

The first is methane dominant SIBO which is associated with constipation. This is sometimes referred to as SIBO - C, similar to IBS - C. And this type of SIBO is not technically caused by bacteria but a single celled organism called archaea. The archaea feed off the hydrogen produced by bacteria during the fermentation of carbohydrates and produce the byproduct methane and methane gas is known to slow transit time in the gastrointestinal tract which leads to constipation and constipation allows more bacteria to grow which causes more methane and more constipation, you get the picture.

SIBO - D is associated with hydrogen production and diarrhea or in some cases alternating constipation and diarrhea. This is the most common form of SIBO and it is the result of carbohydrate fermenting bacteria that produces hydrogen gas in the small intestine. That gas leads to chronic diarrhea, bloating and abdominal pain.

We then have a third type, hydrogen sulfide dominant SIBO, which unfortunately we don't have a test for yet but the symptoms are quite distinct and generally someone with all the symptoms and a negative test result will fall into this category. This type of SIBO occurs through Sulfate reducing bacteria in the small intestine produce hydrogen sulfide which is a highly toxic gas to the cells of the intestinal wall and it's best known for it's distinctively foul odour of rotten eggs.

How SIBO affects your gastrointestinal tract

We now know what SIBO is and what symptoms it results in, but the biggest health issues you are likely to face if you suffer from SIBO are as a result of improper digestion and absorption of vitamins and nutrients. this can occur in multiple different ways. firstly by causing damage to the intestinal wall or intestinal mucosa, which it is sometimes referred to as and this happens because the bacteria and their biofilms and their toxic by products can all damage the microvilli which are the hair like protrusions that line the small and intestines. It can also damage what is known as brush border enzymes which are released by the microvilli, as well as damaging bile acids which are needed to break down and absorb fat.

The other way damage can occur is through bacteria essentially stealing nutrients from your own cells. Most digestion happens in the small intestine while most bacteria lives in the large intestine. But, if you have an overgrowth of bacteria in the small intestine, this creates competition between your own cells and the bacteria. The bacteria may take up certain vitamins such as B12 and minerals such as magnesium, iron and calcium before your own cells have the chance. The bacteria may also consume amino acids from protein which are the building blocks for growth and repair. Therefore, it becomes very difficult to heal and recover in general. Malnutrition is particularly common for SIBO - D sufferers as a common side effect from gut irritation. Food is essentially leaving your body before you have time to absorb any of the good stuff.

The final problem with untreated SIBO is that it can damage your migrating motor complex or MMC in small intestine, and the job of this is to produce wave like motions through the small intestine so that bacteria which is not supposed to be there is moved. This is a big problem in SIBO because it often causes people to relapse unless you correct the problem with the MMC.

So, as you can see there are a lot of problems with SIBO, beyond the symptoms alone which is why for your long-term health managing conditions like this with an indefinite low FODMAP diet is a bad idea.

What about SIFO?

Because our microbiome is not just bacteria there are other types of organisms which can produce similar symptoms but they won't be picked up on through standard testing and may not get better with the standard treatment. Fungi as one of these organisms, Candida being the most common. And a lot of you may have heard of Candida before as it's the same type of fungi causes thrush. It is actually normal to have some amounts of this fungi but in SIFO just like in SIBO, the problem occurs when this fungi overgrows in the small intestine.

The confusing part of this is that the symptoms of practically identical but typical treatment for SIBO may not work for SIFO because treatment is based around killing bacteria instead of fungi. Because there is no test for SIFO you should strongly suspect it if you have a history of yeast infections, rashes, histamine intolerance and if you notice sugar makes your symptoms worse. Or if you are not responding to SIBO treatment then this is when we would consider SIFO as well.

If you suspect you have SIBO, testing and treatment is the next step. In my next blog post, I will be discussing the Gold Standard SIBO testing method I use with my 1:1 clients + my proven method for treating SIBO.

If you want to get the ball rolling now and start your healing journey, book a free 20 min chat with me so we can discuss how I can help you to identify and overcome the root cause of your gut issues.

Talk soon,

Chrystie x

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