The SIBO and the Thyroid Connection

sibo and thyroid

Are you experiencing stomach pains, diarrhea, digestive discomfort, gas, fatigue, or other uncomfortable digestive or body symptoms? You may have SIBO. Small intestinal overgrowth (SIBO) is a condition caused by too much bacteria in your small intestine. While SIBO can lead to a list of symptoms, it may also increase your risk of other health conditions, including thyroid conditions. Yes, that’s right, SIBO and thyroid dysfunction are connected in many cases, and it’s critical that you address both through a holistic treatment approach.

In this article, I will explain what SIBO is. You will learn about its symptoms and causes. I will explain everything you need to know about SIBO and thyroid diagnosis at a functional medicine doctor. You will understand the connection between SIBO and thyroid dysfunction. I will discuss traditional and functional medicine approaches to SIBO and thyroid dysfunction. I will offer my top natural solutions for SIBO and thyroid health.

What Is SIBO?

Small intestinal bacterial overgrowth (SIBO) is a serious condition characterized by too much bacteria in your small intestine. It happens when bacteria that normally would only grow only in other areas of your gut, start growing in your small intestines as well. Your small intestine is the longest part of your digestive tract. This is also the part where nutrients get absorbed into your bloodstream. It is not surprising that SIBO can have serious consequences. It can lead to nutrient malabsorption, malnutrition, damage to the stomach lining, and a list of unwanted symptoms fro diarrhea to abdominal pain. SIBO may also lead to a variety of other health issues. For example, SIBO and your thyroid are closely connected and I regularly see SIBO in thyroid patients. Later in this article, we will discuss the connection between SIBO and thyroid dysfunction (1, 2, 3, 4).

Symptoms of SIBO

The symptoms that come with SIBO are often similar to conditions such as Irritable Bowel Syndrome. Here are some of the commonly seen symptoms:

    • Bloating
    • Gas
    • Abdominal pain or cramping
    • Malnutrition


  • Diarrhea
  • Constipation
  • Nausea or vomiting
  • Belching
  • Food intolerances
  • Weight loss
  • Joint pain
  • Fatigue
  • Skin issues
  • B12 deficiency
  • Fat malabsorption
  • Chronic pain and health issues


The microorganisms and metabolic waste in your gut due to SIBO can be challenging to your health, which can lead to abdominal pain, nausea, gas, diarrhea, constipation, belching, and other gut health symptoms. However, SIBO can lead to an array of health issues. It is connected to irritable bowel syndrome and has been associated with fibromyalgia, Celiac disease, autoimmune conditions, chronic fatigue, neuromuscular issues, liver problems, gallstones, rosacea, gastritis, and thyroid dysfunction. Later in this article, you will learn more about how your thyroid and SIBO connected (5, 6).


Causes of SIBO

SIBO may develop for a variety of reasons. Some of the causes and risk factors of SIBO include (7, 8, 9, 10, 11, 12):

  • Complications of abdominal surgery, such as gastric bypass for obesity or gastrectomy for stomach cancer and peptic ulcers
  • Structural problems in and around your small intestine, such as scars and bulging pouches of tissue
  • Certain medication, including pharmaceutical drugs for Celiac disease, Crohn’s disease, diabetes, radiation enteritis, and scleroderma
  • Low stomach acid that can lead to poor digestion and malabsorption
  • Poor gut motility
  • Intestinal neuropathy, or damage to nerves and muscles in the gut
  • Diverticulosis
  • History of radiation therapy of the abdomen
  • Diabetes 
  • Crohn’s disease, scleroderma, or intestinal lymphoma involving the small intestine
  • An abnormal passageway, or fistula between two segments of the bowel

SIBO Diagnosis

The breath test is the most commonly used test for SIBO which measures the concentration of hydrogen and methane in your breath. Before the test, you have to fast for 12 hours then breathe into a small balloon and repeat it every 15 minutes for 3 hours. Modern medicine practices tend to only use this test for SIBO. Functional medicine practitioners, like myself, take a more comprehensive approach.

Along with the breath test, there are two tests that can help us to understand your gut health better. An organic acid test is a simple urine test that looks at metabolic biomarkers to detect mitochondrial issues, toxicity, neurotransmitter disruption, B vitamin deficiencies, bacterial overgrowth, and yeast overgrowth. A comprehensive stool analysis helps us understand your large intestinal health better. Individuals with SIBO often also struggle with bacteria, parasites, yeast overgrowth, and gut flora imbalance in their large intestines as well. Remember, it is important to look at your entire good health and address it all, not only your small intestines and SIBO. 

In my practice, after going through your symptoms and health history, I do a comprehensive analysis looking at all kinds of markers to understand the state of your health and potential root causes in order to create an individualized comprehensive treatment plan. Whenever a patient comes to my practice with gastrointestinal symptoms I will always check for gut infections, and this includes SIBO. Being that the gut bacteria in our gut plays such a crucial role in the health of every other part of the body, including the thyroid addressing gut health is one of the most important steps in feeling better.

SIBO and Your Thyroid

So, what does SIBO have to do with the thyroid? First and foremost, gut health and thyroid health are connected. Having thyroid issues such as hypothyroidism can actually cause SIBO. When you are dealing with a thyroid condition such as hypothyroidism, your thyroid is not performing the way that it should be. This means that your metabolic processes slow down and this includes digestion. 

One of the most common symptoms of hypothyroidism is constipation. Unfortunately, being chronically constipated can lead to an overgrowth of harmful bacteria. A 2017 study has found that those with constipation-predominant SIBO (SIBO-C) also had thyroid panels with characteristics of hypothyroidism compared to the control group. Not only that, but many people who suffer from hypothyroidism also have lower levels of stomach acid, HCL. HCL helps us digest food so when we do not have enough it can be easy for the pathogenic bacteria in the gut to grow.

There is another connection between SIBO and the thyroid and that is the opposite of what we were just talking about. SIBO can also lead to hypothyroidism. A 2017 study found that hypothyroidism and T4 therapy were linked to a 2.6 and 3.0 times higher risk of SIBO. Since about 21 percent of T4 to T3 conversion occurs in the gut, problems can occur when you do not have optimal gut flora. When your gut is dealing with an overgrowth of harmful bacteria this can cause issues with the T4 to T3 conversion which can then lead to hypothyroidism.

The SIBO and thyroid connection is huge and unfortunately, it can lead to hypothyroidism but hypothyroidism can also lead to bacterial overgrowth. A 2007 study found that 54 percent of participants with hypothyroidism also had SIBO. The best thing to do if you suspect you have either one of these conditions is to work with a functional medicine practitioner, like myself, to get the proper testing to uncover if SIBO is affecting the health of your thyroid. In my practice, I offer extensive gut health testing, and based on your test results, I develop an individualized plan to address each patient’s unique health needs.

But why is it better to work with a functional medicine doctor and take on a holistic approach instead of working with a traditional medicine practitioner? Great question, I will go over everything that you need to know about traditional medicine and functional medicine approach to SIBO and thyroid health (13, 14, 15, 16).

Traditional Medicine Approach to SIBO

Unlike the functional medicine approach that I practice, traditional medicine doesn’t take a holistic approach and doesn’t look at underlying root causes of your symptoms and health problems. Dietary, lifestyle, and environmental factors are often ignored.

If SIBO is detected in a traditional medical practice there is a good chance that a patient will be prescribed antibiotics. The problem with this is that even with the use of antibiotics, SIBO can be very difficult to get under control and a healing dietary and lifestyle protocol need to be put into place. Not including dietary changes can make getting SIBO under control very difficult and you will learn why, so keep reading.

Research has found that people with SIBO who were only prescribed antibiotics actually had a higher recurrence rate. The problem here is that prescription antibiotics may not be enough to really deal with this digestive condition at its source. Dietary, lifestyle, and environmental factors need to be taken into consideration to achieve full recovery and health (17).

The great news is that there is a different way of going about getting SIBO under control and that’s with the use of functional medicine. Let’s take a look at how a functional medicine approach to dealing with SIBO is much different from the traditional medical approach.

Functional Medicine Approach to SIBO & Thyroid Dysfunction

In functional medicine, we use a holistic approach to addressing disease including things like thyroid disease and gut infections. The first step we take is to offer the proper testing to determine if SIBO is causing some or even all of your symptoms. Through these tests, we can uncover the potential root causes of your SIBO and address them appropriately. We will also understand how your other health issues, including thyroid dysfunction, may be connected to SIBO, and create a personalized holistic treatment.

After the test results come back, I often work with patients to eliminate certain foods from their diets such as sugar, refined carbohydrate, gluten, and alcohol. I also recommend a soil-based probiotic supplement. These are important for overall gut health as they will help to give the healthy bacteria in your gut a boost while your body is working to rid itself of the harmful bacteria overgrowth that may be occurring in the small intestine. 

We also work on addressing specific dietary needs and come up with a lifestyle plan to get the SIBO under control as quickly and efficiently as possible. It takes some patience to get SIBO under control but with the right changes, it can be done. If you are also dealing with thyroid dysfunction or other health issues along with SIBO, we continue using the same holistic approach which includes testing, dietary and lifestyle changes, and supplementation.


The FODMAPS diet is a specific dietary approach that many people with SIBO find very beneficial. This diet focuses on removing FODMAPS from the diet. 

FODMAPS are fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. Don’t worry about understanding what each of those terms mean. Just know that FODMAPS are fermentable short-chained carbohydrates and they are not very well absorbed in the gut. They are sugars that are found in certain foods and in those with SIBO they can make symptoms worse. These foods can actually ferment in the digestive tract which is the very last thing you want when you are already dealing with bacterial overgrowth. When these foods ferment, they can feed the bacterial overgrowth and then make your SIBO symptoms worse or make it much more difficult to get this condition under control. 

While some people find this diet helpful, I do not typically use this diet in my practice. Instead, I stick with a diet high in foods like this and typically have great success with this approach:

  • Eggs
  • Grass-fed beef
  • Grass-fed lamb
  • Free-range chicken & turkey
  • Wild-caught fish
  • Cucumbers
  • Lettuce
  • Carrots
  • Bananas
  • Oranges
  • Blueberries
  • Coconut oil
  • Avocado oil
  • Sprouted nut butter

Natural Solutions for SIBO & Thyroid Dysfunction

If you are experiencing symptoms of SIBO and may also have thyroid dysfunction, don’t worry. You can improve your health naturally with some simple yet effective natural solutions. Here are the natural solutions for SIBO and thyroid dysfunction I recommend.

Eat an Anti-Inflammatory, Gut-Friendly Diet

The natural approach to improving SIBO and thyroid imbalance always starts with an anti-inflammatory diet. To tackle SIBO, it is critical that you eliminate sugar, gluten, and refined carbs. Eat smaller meals instead of large ones. Eat 5 to 6 times a day instead of 2 to 3 times. Remove other inflammatory foods, such as caffeine, refined oils, grains, pasteurized dairy, artificial sweeteners, conventional animal products, junk food, and processed foods. 

Eat plenty of greens, vegetables, herbs, spices, and fruits. Eat healthy fats, such as avocado oil, coconut oil, avocados, and sprouted nut butter. Consume high-quality organic animal protein such as grass-fed beef and lamb, free-range, pasture-raised poultry and eggs, and wild-caught fish. Add bone broth and glycine-rich foods, including oxtail, beef shanks, brisket, and chuck roast. Eat plenty of fermented foods, such as sauerkraut, yogurt, kefir, and kimchi for gut health, unless you have histamine intolerance or don’t tolerate probiotic-rich fermented foods well. Drink plenty of clean, purified water.

Take Soil-Based Probiotics

Probiotic supplementation can help to improve gut barrier strength and integrity, lower pathogenic bacteria levels, modulate the immune system, and decrease inflammation throughout the body. Your small-intestines are not supposed to have too much bacteria in it. However, most probiotics contain strains of lactobacillus or bifidobacterium which can add fuel to the fire and compromise your SIBO recovery because they release in your small intestine as well. This is where soil-based probiotics or SBO probiotics come in. Soil-based probiotics do not contain lactobacillus or bifidobacterium strains, yet they still provide all the benefits of a probiotic. I recommend MegaSporeBiotic, a probiotic supplement created without lactobacillus or bifidobacterium (18, 19, 20, 21, 22, 23).

Try Natural Antibiotic Herbal Supplements

Modern medicine treats SIBO with antibiotics. However, there are some natural herbal supplements with antibiotic properties that can support your SIBO recovery. Berberine is a plant alkaloid derived from Oregon grape root and other herbs. It has been known to destroy bacteria and microbes, lower inflammation, and improve your gut lining. Grapefruit seed extract (GSE) is full of anti-oxidant, disease-fighting, antibacterial, and antiviral properties that may benefit your gut health. Oregano oil is a potent antioxidant with natural antibiotic and pathogen-fighting properties that can help to destroy pathogenic bacteria, yeast, and viruses, and improve your gut health (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34).

Try Digestive Enzymes

Digest Care is comprised of a proprietary blend of digestive enzymes along with betaine HCl to support optimal digestion of proteins, fats, and carbohydrates. This product contains the special protease DPP IV (dipeptidyl peptidase IV), which aids in the breakdown of the peptides gluteomorphin (from gluten) and casomorphin (from casein). Digest Care also includes the enzyme lactase, which helps break down the dairy sugar lactose. The use of Digestzymes™ before meals may be helpful when patients experience gas and bloating after eating, constipation, or a feeling of fullness after eating only a small quantity of food.

Improve Your Lifestyle

Chronic stress, poor sleep, and poor lifestyle choices can lead to and increase the symptoms of both gut health issues and thyroid dysfunction. Lower your stress levels and learn to cope with stress better. Practice meditation, journaling, gratitude, breathwork, and yoga. Take healing baths or get a massage. Engage in relaxing activities and spend time with loved ones and positive people. Spend time in nature. Make sure to get some ‘me-time’ in daily, even if it’s just a few minutes. Exercise regularly and lead an active lifestyle. Make sure to get 7 to 9 hours of quality sleep each night.

Try a 30-Day Thyroid Reset

If you are experiencing thyroid dysfunction as a result of or along with SIBO, I recommend a 30-day thyroid reset. To learn more about the Paleo-style anti-inflammatory diet I recommend or if you have Hashimoto’s or another thyroid disease, I recommend reading and following the recommendations in my book, The 30-Day Thyroid Reset Plan: Disarming the 7 Hidden Triggers That are Keeping You Sick. You will learn everything you need to know about thyroid disease. I offer a 30-day plan to improve your health and my favorite thyroid-friendly recipes to nourish your body with delicious meals.

Final Thoughts

Small intestinal overgrowth (SIBO) is a common condition caused by too much bacteria in your small intestine leading to abdominal pain, gas, belching, diarrhea, and a list of other symptoms. it may also increase your risk of other health conditions, including thyroid conditions. SIBO and your thyroid health are connected and SIBO and thyroid issues need to be both addressed. Follow my natural solutions for SIBO and thyroid dysfunction to repair your body and regain your health naturally.

If you are dealing with symptoms of SIBO, Hashimoto’s disease, or other thyroid issues, I invite you to schedule a consultation with me. I can help to identify the root cause of your condition and recommend a personalized treatment plan to repair your body and regain your health and well-being. Schedule your consultation here.

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Hi, I am Dr. Becky Campbell. I work with men and women who’ve had a health set back and are willing to do whatever it takes to reach optimal health so they can perform their best in their careers and be fully present with their family again.

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