The relationship between the gut microbiome and the thyroid exist on a dynamic axis. When one is compromised, the other is affected. Whenever there are disturbances in the gut, it affects the thyroid, and when the thyroid malfunctions, it leads to inflammation and compromised gut health. So the cycle, once in motion, only perpetuates if left unchecked.
When your thyroid is underactive, it is not producing enough thyroid hormone, resulting in an onslaught of symptoms associated with a slowed metabolism. You may experience fatigue, weight gain or difficulty losing weight, intolerance to cold, muscle aches and cramps, constipation, abnormal menstrual cycles and decreased libido. This notable drop in thyroid hormone can affect fertility in a multitude of ways as well, as it plays a role in ovulation and modulating the sex hormones. This could mean anovulatory cycles, luteal phase defects, hyperprolactinemia and sex hormone imbalances.
But all of these effects are not necessarily the result of a deficient thyroid, and so treating the thyroid directly may not even fix the problem. If it does help with your symptoms, but the improvement isn’t great or sustained, that also may indicate that there could be a better solution. In fact it may be this gut-thyroid connection that is the missing link.
Your gut is home to approximately 100 trillion microorganisms that carry out an array of functions on a daily basis. Although some of this bacteria is inherited, it is also greatly influenced by environmental factors, like diet, stress and antibiotics, so the microbiome is constantly changing based on external factors. Interestingly, different people can even respond differently to identical meals. These varying reactions to the same meal is believed to be a result of having unique collections of gut bacteria that respond completely differently to different types of food. When a person’s diet consists of high-fiber and carbohydrates rather than high fiber and animal protein, the overall makeup of the gut bacteria is radically different, as it is necessary to generate energy from different foods in different ways.
These bacteria are not just digesting food; they are also responsible for other processes. Some of the microbiome’s jobs include balancing blood sugar, reducing inflammation, responding to immune threats and converting thyroid hormones into usable forms. When the microbiome is compromised, these actions cannot be sufficiently handled.
As it turns out, 20% of thyroid function depends on what is taking place in the gut. This is where T4 is converted to the usable form of the thyroid hormone, T3. Having a poor diet means that the bad bacteria starts to overtake the good; this can sufficiently hamper this important conversion from taking place. When reserves of T3 are low, you can start to take on the symptoms of hypothyroidism. But when looked at through this lens, the problem is not inherent to the thyroid itself, and if you can correct the imbalance in the gut, you could solve the problem.
But again, it is not so simple to separate the thyroid from the gut. In fact hypothyroidism is one potential cause of leaky gut syndrome or the impermeability of the intestinal lining. This means that undigested food particles can seep into the bloodstream causing an autoimmune response. Hypothyroidism can also cause low stomach acid, which may not sound terribly threatening, but the stomach needs acid to properly digest food. Without the acid, it leaves the food to putrefy in the stomach and again leads back to problems with inflammation and leaky gut.
This is what makes diagnosing thyroid problems so difficult. Because once we are on this loop of poor gut and thyroid health, it’s difficult to know which came first or which to treat. And most often, the first attempts at fixing the problem are centered on the thyroid, doing comprehensive tests and adding supplements, but often all of that effort leads to minimal results because no matter what you do to help the thyroid, if you are not simultaneously helping the gut, the problems will persist or at best not fully resolve.
By improving gut health, you directly improve thyroid autoimmunity, which will improve absorption of any supplements you might be taking to balance the thyroid. Healing your gut will also improve the conversion of T4 to T3, thus reducing your sluggish metabolic symptoms.
But how do you go about healing your gut? Oftentimes what we think of as healthy foods turn out to not be serving our microbiome at all. The best approach is to eliminate foods that cause inflammation. These are foods that people common have sensitivities to:
Once you eliminate these foods, you want to focus on adding foods that can help heal the lining of the gut and to promote a healthy microbiome. High-fiber fruits and vegetables, unprocessed meat and seafood, healthy fats like, avocado and coconut oil, and non-starchy vegetables are all good choices. After a few weeks, you can slowly start to add back the eliminated foods one at a time while paying close attention to how your body responds. If the response is negative, then you’ll know to keep this particular food out of your diet.
We’d also be happy to work with you directly to come up with a custom diet plan that ensures that both your thyroid and gut are happy.
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Weizmann Institute of Science. “Blood sugar levels in response to foods are highly individual.” ScienceDaily. ScienceDaily, 19 November 2015. www.sciencedaily.com/releases/2015/11/151119143445.htm
Rinninella E, Raoul P, Cintoni M, et al. What is the Healthy Gut Microbiota Composition? A Changing Ecosystem across Age, Environment, Diet, and Diseases. Microorganisms. 2019;7(1):14. Published 2019 Jan 10. doi:10.3390/microorganisms7010014