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Intestinal Dysbiosis and Thyroid Health

Published September 8 2014

Intestinal dysbiosis refers to an imbalance of the gut flora.  Just about everyone who has an autoimmune thyroid condition such as Graves’ Disease or Hashimoto’s Thyroiditis has intestinal dysbiosis.  And many people with a non-autoimmune thyroid condition have intestinal dysbiosis as well.  In fact, intestinal dysbiosis is one of the main factors responsible for many chronic health conditions.  In this article I plan on talking about some of the common causes of intestinal dysbiosis, how this can lead to the development of many chronic conditions, and I’ll also discuss a few things you can do to help correct intestinal dysbiosis.

The human gastrointestinal tract consists of many different microbes, which are referred to as the intestinal microbiota.  This microbiota is considered to play a number of key roles in the maintenance of host health, including aiding digestion of otherwise indigestible dietary compounds, synthesis of vitamins and other beneficial metabolites, as well as immune system regulation and enhanced resistance against colonization by pathogenic microorganisms (1) [1].  As a result, if someone has an unhealthy microbiota then this can cause digestive issues, problems synthesizing certain vitamins, and it will weaken the immune system, thus making someone more susceptible to certain pathogens.

I briefly want to mention the gut-associated lymphoid tissue, also known as the GALT.  You might have read elsewhere that 60% to 80% of the immune system is in the gut, and the GALT consists of several types of lymphoid tissue which stores immune system cells such as the T and B lymphocytes.  Some of the lymphoid tissues located within the GALT include the tonsils, adenoids, and Peyer’s patches.  Examples of lymphoid organs outside of the GALT include the spleen and the thymus.  In the GALT, Peyer’s patches play an important role in immune surveillance.  They contain naïve B cells, follicular dendritic cells, and T cell rich areas which all play an important role in immunity (2) [2].  Overall the gut associated lymphoid tissue fences off potentially harmful intestinal antigens from the systemic circulation, and the lymphatic organs play a role the regulation of oral tolerance and intestinal inflammation (2) [2].

What Causes Intestinal Dysbiosis?

There are numerous factors which can lead to an imbalance in the gut flora.  Here are some of the more common ones:

1. Being born via a C-section. Although I realize that there are some cases where Cesarean sections are necessary, unfortunately they have become routine.  Currently about one third of births in the United States are via C-section, and many other countries have high C-section rates as well.  There obviously are numerous benefits of having a natural birth, but one of the most important “benefits” of a vaginal birth is that the baby is exposed to the flora of the mother, and as a result, immediately after birth the infant’s gut becomes colonized with different strains of bacteria.  On the other hand, birth by C-section leads to a delayed colonization in certain species of bacteria (3) [3] (4) [4].  Once again, I realize that there are times when a C-section is necessary, but unfortunately many of these surgeries can be avoided.

However, another thing to keep in mind is that many women have an abnormal vaginal flora.  And so this presents a bit of a dilemma, as while a vaginal birth is preferred, if the pregnant woman has dysbiosis then this of course can affect the health of the baby.  In fact, one study showed that abnormal vaginal flora, bacteria vaginosis, and aerobic vaginitis before 14 gestational weeks can be risk factors for preterm birth (5) [5].  Another study also showed a correlation between a change in the vaginal flora and preterm birth (6) [6].  Antibiotics is a big reason for an abnormal vaginal flora, and one study showed that antibiotic administration during pregnancy leads to alterations in the vaginal flora prior to birth, which can affect the microbial colonization of the baby (7) [7].

2. Formula feeding as an infant. Although I was fortunate to be delivered via a vaginal birth, I wasn’t breastfed as a baby, which set the stage for dysbiosis.  Once again, I realize that in some cases women aren’t able to breastfeed, although this is rare.  When comparing breast milk and formula, there is no question that the nutrient concentrations and compositions are different.  However, breast milk isn’t just important from a nutrient standpoint, but it also is important due to the presence of growth factors, cytokines, immunoglobulins, and digestive enzymes that aren’t in formulas (8) [8] (9) [9].  According to the World Health Organization, exclusive breastfeeding is recommended up to 6 months of age, with continued breastfeeding along with appropriate complementary foods up to two years of age or beyond (10) [10].

And to no surprise the microbiota also differ in those infants who are breastfed when compared to those who are formula fed.  Studies have shown that bifidobacteria are more prominent in the microbiota of breast-fed infants, whereas formula-fed babies have significantly higher proportions of other species (11) [11] (12) [12].

3. Receiving antibiotics. In addition to being formula fed, when I was an infant I also had the privilege of receiving numerous antibiotics due to recurrent ear infections.  I also had plenty of antibiotics growing up, as I have fond memories of taking the delicious “pink medicine”.  Numerous studies have shown that taking antibiotics can have a harmful effect on the gut microbiota (13) [13] (14) [14] (15) [15].  Although antibiotics sometimes are necessary to take, there is no question they are overused and abused, which is one of the main reasons why we now have to deal with antibiotic-resistant strains of bacteria.  My father is one of those people who overuses antibiotics, and has done so for years.  Once again, for certain bacterial infections it can be necessary to take antibiotics, but in many cases a healthy immune system can help fend off these infections.  Of course most people who have intestinal dysbiosis don’t have a healthy immune system, and so hopefully after reading this article you will do things to help increase your immunity.

4. Poor diet. Dietary changes are known to affect both the composition and function of the gut microbial communities, which in turn can alter the innate and adaptive immune system (16) [16].  As I mentioned earlier, breastfed infants will have a different microbiota than formula fed infants.  However, diet can also affect the composition of the gut microbiota later in life (17) [17].  Not surprising, eating a “Western” diet consisting of plenty of refined foods and sugars can cause dysbiosis (18) [18].

5. Other Factors. There is also evidence that chronic stress can affect the microbiota (19) [19] (20) [20] (21) [21].  So this is yet another way that stress can lead to the development of an autoimmune condition.  Surprisingly I didn’t find much on the relationship between environmental toxins and gut dysbiosis, although I did find one study on cadmium exposure and how this toxin can cause intestinal dysbiosis (22) [22].  I’m pretty confident that there will be additional studies in the future involving different toxins which show the detrimental effects they have on the microbiota.  After all, there are tens of thousands of chemicals in our environment, and just because studies haven’t been conducted on the relationship between these toxins and the microbiota doesn’t mean that they can’t cause intestinal dysbiosis.

Intestinal Dysbiosis and Thyroid Autoimmunity

In the past I’ve discussed the importance of twin studies, and how they show that  if one twin has an autoimmune condition, the other twin has approximately a 30% chance of developing the same condition.  The exact percentage varies depending on the specific autoimmune condition, but the point I’m trying to make is that environmental factors play a greater role than genetics when it comes to the development of these conditions.  And differences in the microbiota of twins may play a role in the development of chronic health conditions (23) [23].

Many people don’t understand how important the gut is when it comes to the immune system.  In previous articles I’ve spoken about how having an increase in intestinal permeability (a leaky gut) can trigger an autoimmune response.  But even if someone doesn’t have a leaky gut, if they have intestinal dysbiosis this can affect the health of the immune system, and set the stage for a condition such as Graves’ Disease or Hashimoto’s Thyroiditis.  Numerous studies have shown that individual species of the microbiota can induce very different types of immune cells (e.g., Th17 cells, Foxp3+ regulatory T cells) and responses, can have a significant impact on the systemic immune response, and have been shown to affect disease development in areas other than the gut (24) [24].

I’ve written a blog post entitled “Regulatory T Cells and Thyroid Autoimmunity [25]“, and in the post I spoke about the importance of regulatory T cells in the prevention of autoimmunity.  A healthy immune system will have many of these regulatory T cells.  And the composition of the intestinal microbiota will play an important role in regulating these regulatory T cells (25) [26] (26) [27].  As a result, if someone has both intestinal dysbiosis and a genetic predisposition for Hashimoto’s Thyroiditis or Graves’ Disease, then this imbalance in the gut flora can potentially lead to the development of one or both of these conditions.

Although there are numerous studies which show the connection between the intestinal microbiota and autoimmunity (27) [28] (28) [29] (29) [30], as of writing this article I was only able to come across one journal article which specifically discussed the potential relationship between thyroid autoimmunity and the gut microbiota (30) [31].  This discussed the potential role of intestinal dysbiosis in the development of Hashimoto’s Thyroiditis.  Although more research needs to be conducted, and without question will be in the upcoming years, the evidence seems strong when it comes to a potential role of gut dysbiosis and autoimmunity.

How To Correct Intestinal Dysbiosis

Since diet, chronic stress, and toxic exposure can lead to intestinal dysbiosis, then it of course makes sense to modify these lifestyle factors.  Eating whole foods and avoiding the refined foods and sugars is obviously important to restore the health of the gut.  It also is a good idea to eat plenty of fermented foods.  Although some people do well when consuming fermented dairy such as yogurt and kefir, many people react to the proteins of dairy.  As a result, it probably is best to initially stick with fermented vegetables such as sauerkraut and kimchi.  In addition to eating fermented foods, I still think it’s a good idea to take a good quality probiotic supplement.  This is especially true if the dysbiosis was caused by taking antibiotics.  But even if antibiotics wasn’t a factor it still is a good idea to take a good quality probiotic.

And if chronic stress is a factor, which is the case with most people, then this of course should be addressed.  Earlier I mentioned how there aren’t too many studies which demonstrate a relationship between toxins and dysbiosis.  However, for obvious reasons I think it’s important for everyone to minimize their exposure to toxins, and to do things to help eliminate toxins from their body.

Since having an unhealthy microbiota can make the person more susceptible to certain pathogens, this of course is something that needs to be addressed.  One of course can conduct certain testing to detect pathogens, such as a stool panel to look for bacterial infections, yeast, and parasites.  Although I do use these tests from time to time, they are expensive, and false negatives are possible.  In other words, someone might have parasites, yet test negative for them.  False negatives are minimized by having the patient collect a stool sample on three different days, although the possibility for false negatives still remain.  Plus, although these stool panels are pretty comprehensive, you need to keep in mind that they don’t test for every pathogen.  Another test which can evaluate some of the markers of intestinal dysbiosis is an organic acids test.  As for how to naturally eradicate pathogens, I’ll refer you to a previous article I wrote entitled “The Role of Pathogens In the Development of Graves’ Disease and Hashimoto’s Thyroiditis [32]“.

However, while taking herbs and supplements to eradicate certain pathogens is sometimes necessary, one of the best things you can do to prevent intestinal dysbiosis from occurring is to improve the health of your immune system.  And of course the best way to accomplish this is by eating well, managing your stress, getting sufficient sleep, and minimizing your exposure to environmental factors.  Hypochlorhydria (low stomach acid) also can lead to an increase in intestinal dysbiosis, and so this also needs to be considered.  Obviously there can be other factors which can cause dysbiosis, many of which I mentioned in this article, and unfortunately we can’t control all of these.  For example, if you were born via a C-section and/or weren’t breastfed as a baby then this will affect your health as an adult.  But even if this was the case you can still do things to improve the health of your immune system, such as eating well, consuming fermented foods and probiotic supplements, do a good job of managing your stress, etc.

In summary, many people with thyroid and autoimmune thyroid conditions have intestinal dysbiosis.  Having intestinal dysbiosis not only can lead to digestive symptoms, but it can also interfere with the synthesis of certain vitamins, and will weaken immunity.  Some of the factors which can cause intestinal dysbiosis include being born via a C-section, not being breastfed, receiving antibiotics, eating a poor diet, chronic stress, and toxic exposure.  Because the intestinal microbiota helps to regulate the cells of the immune system, one of these being regulatory T cells, having intestinal dysbiosis can cause immune system dysregulation and thus lead to a condition such as Hashimoto’s Thyroiditis or Graves’ Disease.  In order to correct intestinal dysbiosis one needs to focus on improving the health of the immune system, although certain supplements and herbs to eradicate pathogens might be necessary at times.