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Can SIBO Trigger Thyroid Autoimmunity?

Many people reading this are familiar with small intestinal bacterial overgrowth, which is also known as SIBO.  This involves an overgrowth of bacteria in the small intestine, and can lead to symptoms such as bloating, gas, and abdominal pain, along with diarrhea and/or constipation.  Although SIBO is more common in people with Hashimoto’s Thyroiditis, I have also seen it in patients with Graves’ Disease as well.  But can SIBO trigger an autoimmune thyroid condition?

Numerous pathogens have been associated with thyroid autoimmunity.  This includes H. Pylori, Yersinia enterocolitica, Lyme disease, Epstein barr, and parasites such as Blastocystis Hominis.  However, it’s important to understand that SIBO isn’t a pathogenic infection.  This condition involves having good bacteria in the wrong place, as most of the bacteria should be located in the large intestine, and only a small amount should be located in the small intestine.  But for numerous reasons that I’ll discuss in this blog post, there can be an overgrowth of bacteria in the small intestine.

As a result, small intestinal bacterial overgrowth itself doesn’t seem to be an autoimmune trigger.  However, there are a few things to keep in mind.  Some cases of SIBO are due to an autoimmune process, which I’ll describe below, and having one autoimmune condition can make someone more susceptible to having another autoimmune condition.  So perhaps having SIBO can lead to another autoimmune condition such as Graves’ Disease and Hashimoto’s Thyroiditis, but the correlation hasn’t been made yet.  But even if this isn’t the case, SIBO can cause an increase in intestinal permeability (a leaky gut), and this in turn can set the stage for the development of an autoimmune thyroid condition.

What Causes SIBO?

There are numerous factors which can cause someone to develop SIBO, and so let’s take a look at some of these:

1. Dysfunction of the migrating motor complex (MMC).  This is the main reason why people develop SIBO.  The MMC is a small wave that cleanses the small intestine of debris.  And so if the MMC isn’t working properly then bacteria and other debris are no longer swept through the lumen of the small intestine.  Food poisoning is the most common cause of a dysfunctional MMC, but other causes include hypothyroidism, diabetes, or an infection such as C. difficile, giardia, or Lyme disease.  Certain drugs such as opiates and antibiotics can also affect the MMC.

2. Altered anatomy.  This can interfere with the clearance of bacteria.  For example, adhesions due to surgery or endometriosis are potential causes of SIBO.  Other anatomical anomalies include a narrowing of the small intestine, fistulas, and diverticuli.

3. Hypochlorhydria (low stomach acid).  Millions of people take acid blockers, and this is a big problem.  Besides being necessary to break down nutrients, stomach acid also can help to eradicate harmful pathogens, and prevent the overgrowth of bacteria.  However, you don’t need to take acid blockers to have low stomach acid, as having a hypothyroid condition alone can result in the decreased production of stomach acid.  Stress can also decrease the production of stomach acid.

4. Absent or inefficient Ileocecal valve.  The ileocecal valve is the barrier that separates the small intestine from the large intestine.  It prevents backflow from the large intestine into the small intestine.  If this is absent or dysfunctional then it can cause the bacteria from the large intestine to migrate into the small intestine, thus leading to SIBO.

What Is The Relationship Between IBS and SIBO?

Infectious gastroenteritis, more commonly known as food poisoning, can result in the production of toxins by bacteria that can damage the nerves which play an important role in gut motility.  The specific name of the toxin is cytolethal distending toxin (CDT).  What happens is the immune system forms antibodies to this toxin (called anti-CDTb antibodies), but anti-vinculin antibodies are also produced.  Vinculin is a protein that helps connect the interstitial cells of Cajal (ICC) so that they can communicate properly to help the MMC .  When someone has the CDT-b toxins these harm the ICC, and in a case of mistaken identity the immune system attacks vinculin, which has a negative effect on gut motility.

So to summarize, food poisoning is the most common cause of irritable bowel syndrome with diarrhea (IBS-D).  This in turn has a negative effect on gut motility, and the problem with gut motility is what leads to small intestinal bacterial overgrowth.  There is a blood test called IBSchek by Commonwealth Laboratories that can determine if someone has IBS-D associated with anti-CDTb and anti-vinculin antibodies.

How Is SIBO Diagnosed?

Although one’s symptoms can provide a lot of valuable information, if SIBO is suspected then it is a good idea to test.  And the way it is detected is through a breath test.  With the breath test the patient fasts overnight, and then in the morning they will start with a baseline breath test, followed by the consumption of a substrate (i.e. lactulose or glucose).  After the baseline breath test they will measure a breath sample approximately every 20 minutes, and what the lab is looking for is bacterial fermentation, and it measures this fermentation by measuring the levels of hydrogen and methane. In other words, if someone has SIBO, there will be more fermentation, which will lead to higher levels of hydrogen, methane, or both gases. Let’s take a look at the two main breath tests used:

Lactulose breath test.  Lactulose can’t be absorbed by humans, but can be broken down by bacteria.  As bacteria consume lactulose they produce hydrogen and/or methane gases, which are measured with the breath test.  This is most commonly used because it can diagnose SIBO in the distal end of the small intestine.

Glucose breath test.  The glucose breath test seems to be more accurate, but the reason this test isn’t as commonly used is because glucose is absorbed in the beginning of the small intestine.  As a result, if someone has SIBO that is occurring in the distal small intestine then it is less likely to be detected.  However, some bacteria don’t ferment lactulose, and as a result, if SIBO is suspected yet the lactulose test comes back negative then you should consider doing a glucose breath test.  Another option is to do both the lactulose and glucose tests initially, although many labs don’t offer both types of testing.

Can A Stool Panel Detect SIBO?

Hydrogen and methane are produced by bacteria, and this is what’s being measured on the breath tests.  Methanobrevibacter smithii is a bacteria that accounts for most of the methane production in the body.  Some comprehensive stool panels test for this “methanogenic” bacteria, and if this is high then this might suggest that someone has SIBO.  However, this isn’t conclusive, and the breath test remains the gold standard for determining if someone has SIBO.

What Health Conditions Are Associated With SIBO?

Below I have listed some of the other health conditions associated with SIBO.  This doesn’t mean that SIBO is always responsible for the development of these conditions, but if you have any of the following conditions then SIBO is a possible cause.

What’s The Ideal Diet For Those With SIBO?

Although I like my patients with Graves’ Disease and Hashimoto’s to start on an autoimmune paleo diet, in the past I have written blog posts which discuss how there is no diet that fits everyone perfectly.  And the same concept applies with SIBO.  While all cases of SIBO involve the overgrowth of bacteria into the small intestine, the bacteria will differ from person to person.  As a result, one person with SIBO might be able to tolerate foods that someone else with SIBO can’t tolerate, and vice versa.  In addition, some people might be able to eat small quantities of a certain food, but if they eat larger quantities they experience bloating and gas.  With that being said, there are certain diets that people with SIBO should consider following, although there will be some modifications depending on the person.

Below I’m going to discuss the different diets that are recommended for patients with SIBO.  The primary goal of each of these diets is to feed the person while starving the bacteria.

Low FODMAP diet.  This probably is the most well known diet when it comes to SIBO, and because of this, many healthcare professionals will put their patients with SIBO on this type of diet.  FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols.  Examples of high FODMAP foods include fermented foods (i.e. sauerkraut), starch (grains, beans, starchy vegetables), soluble fiber (grains, beans, fruits, vegetables), sugar (fruit, agave), and resistant starch (legumes, whole grains).

This doesn’t mean that everyone with SIBO needs to avoid all of these foods.  For example, some people with SIBO are able to tolerate sauerkraut, while others can’t eat any fermented foods without experiencing gas, bloating, and other symptoms.  Some people are able to eat small amounts of these foods, while others are unable to tolerate certain foods altogether.  And so you need to listen to your body.

Specific Carbohydrate Diet.  The Specific Carbohydrate Diet (SCD) is similar to a Paleo diet in that it allows meat, fish, eggs, nuts, seeds, vegetables, and fruit.  However, it differs in that it does allow some lactose-free dairy and certain beans.  The dairy products that are allowed include yogurt, aged cow and goat cheeses, butter, ghee, and cottage cheese.  The allowed beans include white beans, navy beans, lentils, split peas, lima beans, kidney beans and black beans.  In order to make the beans easier to digest you want to soak them overnight.  For more information I would read the book “Breaking The Vicious Cycle [1]”, or you can visit the website www.scdlifestyle.com [2].

GAPS diet.  GAPS stands for Gut and Psychology Syndrome, and the diet was developed by Dr. Natasha Campbell-McBride.  The diet is very similar to the Specific Carbohydrate Diet, and involves minimal supplementation.  The only legumes allowed on the GAPS diet include lentils, split peas and white navy beans, and they need to be soaked first.  Dairy is initially eliminated, but then the person is allowed to slowly reintroduce ghee, followed by butter, yogurt, sour cream, kefir, hard cheese, and cream.  One of the main differences between the GAPS diet and the Specific Carbohydrate Diet is that the GAPS diet involves going through a 6-stage introduction diet before moving onto the “full” GAPS protocol, which is usually followed for one or two years.

SIBO Specific Diet.  This is a diet created by Dr. Allison Siebecker, and is a combination of the Specific Carbohydrate Diet and the low FODMAP diet.  While it’s a great diet for those who have SIBO, it’s important to understand that this a very restrictive diet, and as a result, Dr. Siebecker first recommends to try one or more of the other diets listed above first, and if you don’t do well with the other diets then you might want to consider giving this diet a try.   For more information I would visit www.siboinfo.com/diet [3].

Elemental diet.  The elemental diet can be the most effective diet when it comes to alleviating the symptoms of SIBO.  However, it is arguably the most challenging diet to follow.  It’s considered an antimicrobial approach because the goal is to starve the bacteria, but supply the person with sufficient nutrients in an easily absorbed form.  It essentially consists of protein, fat, carbohydrates, amino acids, vitamins, minerals, and either glucose or maltodextrin.  You can get a premade formula from a company such as Integrative Therapeutics, or if you visit www.siboinfo.com [4] and visit the resources page you can get a recipe to make your own.  The elemental diet can help to lower both methane and hydrogen levels and typically you want to follow it for 2 or 3 weeks, and then do another breath test immediately upon completion of it.

Should Someone With Graves’ Disease or Hashimoto’s Also Follow An AIP Diet?

Many people with Graves’ Disease and Hashimoto’s Thyroiditis follow an AIP diet, and they might want to know if they should continue following an AIP diet when trying to address SIBO.  So for example, should they follow an AIP diet and a low FODMAP diet?  Doing this is extremely difficult, and what you usually want to do is prioritize the eradication of SIBO.  In other words, it’s usually okay to stray from the AIP diet while trying to address SIBO, and this falls into the “Remove” category of the 5-R protocol I mentioned in a previous blog post [5].  Then once the bacterial overgrowth has been “removed” you can focus more on gut healing by following the AIP diet, along with eating gut-healing foods (i.e. bone broth) and taking certain nutrients (i.e. L-glutamine).

Eradicating SIBO Through Drugs and Herbs

In order to eradicate SIBO there are two main methods used: prescription antibiotics and natural antimicrobials.  Let’s look at the pros and cons of each.

Prescription antibiotics.  Rifaximin is the antibiotic most commonly recommended for SIBO.  While I’m not a big fan of antibiotics, Rifaximin is different than most other antibiotics.  First of all, it stays in the small intestine, which means that it doesn’t harm the beneficial bacteria in the large intestine like most other antibiotics do.  In fact, there is evidence that Rifaximin can actually increase good bacteria (i.e. bifidobacteria) in the large intestine.  In addition, bacterial resistance isn’t too common when using Rifaximin.  With that being said, not everyone with SIBO will respond to Rifaximin.

Herbal antimicrobials.  I personally prefer to use herbal antimicrobials when dealing with SIBO.  Some of the natural agents which can help to eradicate SIBO include berberine, oregano oil, neem, and allicin.  Keep in mind that while garlic is a high FODMAP food, most people with SIBO can tolerate an allicin supplement, although not everyone.  Although I personally haven’t used pomegranate as of writing this blog post, Dr. Nirala Jacobi has a lot of experience with SIBO and has been experimenting with pomegranate as an antimicrobial.  As for whether the herbs are as effective as Rifaximin, there actually was a study that showed that herbal therapy is equivalent to Rifaximin for treating SIBO (1) [6].  However, just as is the case with Rifaximin, not everyone with SIBO will respond to the herbal antimicrobials.

What To Do When Rifaximin or The Natural Antimicrobials Don’t Work

So what should be done if someone takes either Rifaximin or the natural agents and doesn’t improve?  Well, it is important to do another SIBO breath test after completing a round of treatment.  On the retest, if the gas levels have decreased a good amount but are still high then it makes sense to do another round of the Rifaximin or natural antimicrobials, regardless if the person’s symptoms have improved or not.  On the other hand, if the gas levels haven’t improved then it probably is wise to try a different treatment approach.  If the gas levels have normalized and the person is still symptomatic then this is usually an indication that there is something else going on besides SIBO, and additional testing might be indicated.

The Role of Prokinetics In Preventing a Relapse

Prokinetics help to stimulate the MMC, and since most cases of SIBO are caused by a dysfunctional MMC, taking prokinetics can be important to prevent a relapse after receiving treatment for SIBO.  It’s also important to understand that the MMC works in a fasting state, and so while I commonly recommend for patients to eat regularly throughout the day to help stabilize the blood sugar levels, those with SIBO probably shouldn’t snack in between meals, and should go at least 12 hours overnight without eating.

As for what prokinetics you should take, I used to recommend an herbal formulation called Iberogast, but it seems as this is being discontinued.  Ginger can be a good prokinetic, and 5-HTP also can be helpful.  Many reading this are familiar with low dose naltrexone, and this can also act as a prokinetic.  For those who aren’t familiar with LDN you can read the article I wrote entitled “Low Dose Naltrexone and Thyroid Autoimmunity [7]“.  Erythromycin is commonly used as an antibiotic, but in very low doses it can also help to stimulate the MMC (2) [8].

How long should someone take a prokinetic for after SIBO has been eradicated?  It depends on the person, as most will need to take it for at least 3 to 6 months.  And if someone has autoimmunity to vinculin then they might have to take prokinetics on a permanent basis.  I mentioned earlier how if someone has the CDT-b toxins these harm the ICC, and in a case of mistaken identity the immune system attacks vinculin.  And until we figure out how to stop the autoimmune process then the person will most likely have to continuously take prokinetics.

Can Someone With Graves’ Disease or Hashimoto’s Get Into Remission By Eradicating SIBO?

As I mentioned earlier in this post, SIBO doesn’t seem to be a direct trigger of thyroid autoimmunity.  However, SIBO can cause an increase in intestinal permeability, which is a factor in autoimmune conditions such as Graves’ Disease and Hashimoto’s Thyroiditis.  Because of this, one can argue that if someone has SIBO and a leaky gut, then in order to heal the gut it is necessary to eradicate SIBO, and if the trigger is also removed then this can put the person into remission.  And so while eradicating SIBO might be necessary for healing a leaky gut, in order to get someone with an autoimmune thyroid condition into remission it is still necessary to find and remove the trigger.

In summary, small intestinal bacterial overgrowth can be present in people with Hashimoto’s Thyroiditis and Graves’ Disease.  The most common cause of SIBO is dysfunction of the migrating motor complex.  SIBO is usually diagnosed with either the lactulose or glucose breath test, although false negatives are possible with either test.  Some of the common diets recommended for those with SIBO include the low FODMAP diet, the Specific Carbohydrate Diet, the GAPS diet, the SIBO Specific Diet, and the Elemental diet.  Although antibiotics such as Rifaximin are commonly given to people with SIBO, herbal antimicrobials can be equally effective in many people.  And taking prokinetics can be important to prevent a relapse from occurring after receiving treatment for SIBO.