If you have hypothyroidism and gut issues, you may want to get tested for a condition called small intestinal bacterial overgrowth (SIBO).
In this article, we’ll explain the relationship between SIBO and hypothyroidism and how treating the root cause of each of these conditions can help you eliminate symptoms.
What is SIBO?
SIBO stands for small intestinal bacterial overgrowth and occurs when too many bacteria end up in your small intestine. While your gut is home to billions of bacteria, most of them are supposed to reside in the large intestine, or colon. SIBO may be caused by low stomach acid, an episode of food poisoning, or recurrent antibiotic use.
SIBO is associated with many different health conditions, like irritable bowel syndrome, acne
, and hypothyroidism.
Testing for SIBO
The main test to diagnose SIBO is a breath test. In a SIBO breath test, you drink a specific syrup and provide breath samples at various time intervals. The bacteria in your small intestine feed on the syrup and produce hydrogen and/or methane gas. If the levels of gas are higher than the provided threshold, this may indicate a SIBO diagnosis. There are also different types of SIBO, so it is possible that a conventional breath test may miss the diagnosis.
The combination of symptoms plus looking at the microbiome can also be useful to make a clinical diagnosis of SIBO. A stool test may also help assess the bacteria in the large intestine to tell us if there are other gut issues like candida (yeast) overgrowth or parasites.
What is Hypothyroidism?
Hypothyroidism is a fairly common condition affecting nearly 12 percent of all Americans at some point in their life. Plus, women are five to eight times more likely to develop a thyroid condition than men (1
). Commonly referred to as an “underactive thyroid”, hypothyroidism occurs when your thyroid gland does not make enough thyroid hormones to meet your body’s demand. Thyroid hormones regulate many vital body functions like metabolism, growth and development, heart rate, body temperature, and more.
An autoimmune condition called Hashimoto’s is the most common cause of hypothyroidism in the United States. Common symptoms of hypothyroidism include fatigue, brittle nails, thinning hair, weight gain, heavy or irregular periods, and cold intolerance.
Testing for Hypothyroidism
Your doctor can diagnose hypothyroidism with a simple blood test looking at your TSH and free T4 levels. A high TSH level with or without a low free T4 first confirms the presence of hypothyroidism.
The conventional range for a normal TSH level is approximately 0.5 - 4.5 mIU/L. However, functional medicine practitioners often prefer a narrower and more optimal range for TSH of 1.0 - 2.5 mlU/L. Using this smaller range may help to identify more thyroid problems, like Hashimoto’s. The additional presence of thyroid antibodies in your blood suggests a Hashimoto’s diagnosis in which the body’s immune system attacks the thyroid gland.
If you suspect a thyroid issue, it is important to request a full thyroid panel to include:
- Free T4
- Free T3
- Thyroid Peroxidase Antibodies (TPO Ab)
SIBO and Hypothyroidism
Your thyroid hormones influence gut motility. This is the amount of time it takes for food to pass through the digestive tract. Without enough thyroid hormones, gut motility is slowed. Unfortunately, slow gut motility increases the risk of developing SIBO. Therefore, it may come as no surprise that SIBO is common in patients with hypothyroidism (2
). One study found over 50 percent of the subjects with hypothyroidism also had SIBO compared to just 5 percent of healthy controls (3
Treatment of SIBO and Hypothyroidism
Like all conditions, we strive to identify and treat the root causes of SIBO and hypothyroidism. Unfortunately, treating SIBO can be difficult and may require use of specific antibiotics and/or herbal antimicrobials. On the other hand, the treatment for hypothyroidism may seem relatively straight-forward with a simple prescription for thyroid hormone replacement. However, given that the most common cause of hypothyroidism is Hashimoto’s (autoimmune thyroid disease), we also focus on calming and supporting the immune system. If you suspect either of these conditions, we recommend speaking with your doctor. In the meantime, here are a few basic tips to support optimal thyroid function and gut health:
Eat regularly scheduled meals
Your intestines move food through the digestive tract with cyclic muscle contractions known as “cleansing waves.” These are essential movements that also propel bacteria through the intestines. To support optional cleansing waves, avoid constant snacking or nibbling throughout the day. Instead, set regularly scheduled meals and snacks that will keep you full and satisfied. Depending on the individual, we may also recommend a form of time-restricted eating at night. Read more about intermittent fasting and hypothyroidism
Support optimal digestion
Digestion is a multiple step process that requires adequate levels of stomach acid, enzymes, and bile. Low levels of these necessary digestive factors may cause or worsen SIBO. To support digestion, eat slowly and chew your food thoroughly. You may also consider using our digestive enzymes
with each meal.
Root’s supplement protocol* for SIBO often includes:
Microbiome balance: 1 each morning before breakfast for one bottle to gently remove overgrowth.
Root Digestive enzymes: one with each large meal up to three times a day taken for about 3 months or as desired.
Gut Health Rebalance: for essential soothing and gut rebuilding nutrients, one scoop in water daily taken for about 3 months or as desired.
*We do NOT use this protocol in pregnancy. These statements have not been evaluated by the FDA. These products are not intended to "diagnose, treat, cure or prevent any disease.
In month two, we would start with a good probiotic and immunoglobulin combination to repopulate good bacteria and help the intestinal cells repair themselves, taken for about 3 months or as desired.
Increase dietary fiber
Fiber is the preferred source of fuel for your beneficial gut bacteria. Eating fiber-rich foods with our meals and snacks ensures the survival and growth of good gut bacteria. You should aim to eat at least 25 grams of fiber per day. The best sources of fiber generally include fruits, vegetables, legumes, nuts, and seeds. If you have trouble tolerating fiber, talk with your doctor about obtaining a SIBO test.
A note on Low FODMAP diets. Sometimes a lower FODMAP diet is used temporarily to help with symptoms. However, a Low FODMAP diet is not meant to be a long term solution and is often not necessary after treating root causes. If your doctor advised a Low FODMAP diet and you aren't sure how to begin, we created a digital Ebook reviewing this here: https://rootfunctionalmedicine.com/product/lowfodmapdiet
Limit added sugar
Added sugar disrupts your gut bacteria by feeding the harmful bugs and starving the good bugs.
The largest sources of added sugar in the standard American diet are sugar-sweetened beverages and desserts or sweet snacks. Aim to reduce or eliminate regular intake of these items. Examples of sugar-sweetened beverages include sweetened coffee, soda, juice, and sweet tea. Many beverages contain high amounts of sugar even if they are marketed as “healthy” options, so consider checking the “added sugar” line on the nutrition label as well.
SIBO and Hypothyroidism: Takeaways
SIBO occurs when too many bacteria end up in the small intestine. Hypothyroidism occurs when your thyroid gland does not produce enough thyroid hormones to meet the body’s demand. Individuals with hypothyroidism are more likely to also have SIBO. If you have hypothyroidism and gut symptoms, consider seeking further testing to rule out SIBO. You can support optimal gut and thyroid health by eating regularly scheduled meals that are rich in dietary fiber, limiting added sugar, and supporting optimal digestion as needed with digestive enzymes, bile extract, and/or HCl.