Researchers generally agree that the key problem in fibromyalgia is a change in how pain signals from the skin, joints and muscles are processed in the brain, leading to the characteristic and diagnostic long-term, body-wide pain. (1, 3) But, to date, no one has been able to definitively prove what causes these changes, and how. (3, 4)
However, growing evidence suggests that fibromyalgia may be caused by poor gut health — specifically, by a condition called “small intestinal bacterial overgrowth (SIBO)”, in which colon bacteria begin colonizing the normally relatively sterile environment of the small intestine. (5)
Let’s explore this growing body of evidence, what it means, and it’s possible implications for ways to address fibromyalgia symptoms.
Fibromyalgia, SIBO and the Breath Test
The most direct, and perhaps the most important, evidence supporting the idea that fibromyalgia may be caused by SIBO came from a 2001 study by researchers at Cedar-Sinai Medical Center which first linked the two conditions. (6) Inspired by epidemiological studies that showed extremely high rates of gut dysfunction in people with fibromyalgia, (7, 8, 9) the researchers decided to look at the state of their intestinal health more closely. Close examination of the epidemiological studies showed that gastrointestinal symptoms reported by fibromyalgia patients were similar to the symptoms seen in Irritable Bowel Syndrome (IBS). (7, 8, 9)
Since previous work in the Cedar-Sinai lab had established strong links between SIBO and IBS, they thought looking for SIBO in fibromyalgia patients may be a smart place to start. (10)
So, they put it to the test!
They organized a group of 123 volunteers with fibromyalgia to undergo SIBO breath testing. Results showed that nearly 80% of the group tested positive for SIBO, a much higher rate than seen in healthy groups of volunteers, or even in groups of individuals with IBS. (6)
Though not conclusive proof of a direct link, this data was a huge tip-off that it might be a relationship worth looking into further.
Does SIBO Cause Fibromyalgia?
To determine if there was a causal relationship between SIBO and fibromyalgia, researchers set up an experiment that compared markers of SIBO severity to markers of fibromyalgia severity. If one condition causes another, generally you would expect that increasing the severity of that condition would directly cause a worsening of the other.
As a marker for SIBO severity, researchers used the amount of hydrogen detected in a SIBO breath test. Since the hydrogen detected in the test is made by the bacteria in SIBO, greater levels of hydrogen generally indicate greater numbers of bacteria. And as a marker of fibromyalgia severity, they used self-reported pain levels. (5)
When the data was analyzed, they found that, consistent with a causal relationship, greater levels of hydrogen production were associated with greater reported pain levels. (5)
Now the question remained: did SIBO cause fibromyalgia or did fibromyalgia cause SIBO?
In order to figure this out, researchers took a step back and took a look at all the evidence linking gut health, gut bacteria, brain function and pain regulation and asked themselves: which direction makes more sense? Which one does the scientific literature support more?
The clear answer here was — SIBO is more likely to cause fibromyalgia than the other way around. Close examination of all the evidence allowed researchers to find two step-by-step mechanisms by which SIBO could cause the symptoms of fibromyalgia.
Let’s look at them both!
SIBO May Cause a Tryptophan Deficiency
Tryptophan is one of the 20 standard amino acids and your body uses it to help build proteins. It is also absolutely critical for making an important chemical messenger used to carry nerve signals through the brain called serotonin. It is so important, in fact, that changes in tryptophan levels in your body is sufficient to directly change levels of serotonin in your brain. (11)
One of serotonin’s jobs in the brain is to modulate signals that control the sense of pain. (12) Based on the symptoms of fibromyalgia, it was suspected that serotonin signaling might play a role in the disorder. And, indeed, when researchers compared those with fibromyalgia to those without the pain disorder they found that people diagnosed with fibromyalgia consistently had lower levels of serotonin in their bodies. (13, 14, 15, 16)
So, how might SIBO be able to lower tryptophan and serotonin levels?
Well, tryptophan belongs to a group of amino acids called “essential amino acids.” This means that your body can’t make tryptophan by itself; you have to get all of it by absorbing it from the food you eat. SIBO can decrease your ability to absorb tryptophan in three ways:
1. By using up tryptophan from your food
Like us, bacteria use tryptophan to build proteins and keep their cell machinery functioning properly. They can even take it out of the food we eat, just like we can. (17) It doesn’t matter when bacteria do this to food in your colon because you’ve already absorbed what you needed while the food was still in your small intestine.
When colon bacteria move into your small intestine, though, like they do in SIBO, they may use up some of the tryptophan before you get a chance to absorb what you need, driving the levels of tryptophan in your body down. (17)
2. By damaging the lining of your small intestine
SIBO can damage the lining of your small intestine, where tryptophan should be absorbed. This damage may make it difficult for your intestines to absorb the tryptophan not snatched up by the bacteria normally. (17)
3. By decreasing sugar absorption
Changes in the function of your small intestine may also be able to decrease the ability of your body to absorb free sugars. Too many free sugars in your small intestine may directly impair tryptophan absorption. (16)
This is because free sugars, particularly free fructose, can react with tryptophan to create sugar-tryptophan complexes. These complexes are too big to be transported through the intestinal wall the way tryptophan normally is, so they can’t be absorbed. (16)
This, of course, may lower the amount of tryptophan absorbed by the body, and, in turn, lower serotonin levels. (16)
This theory of the development of fibromyalgia is supported by epidemiological studies which consistently show that the disorder is overwhelmingly seen in women; around 96% of those with fibromyalgia are women. (13)
Women’s bodies are less efficient at making serotonin out of tryptophan than men’s. This means that women need higher levels of tryptophan from their diets to make the same amount of serotonin. It also means that decreases in tryptophan absorption lead to a drop off in serotonin levels more quickly in women than men. If tryptophan deficiency were a driving cause behind fibromyalgia, one would indeed expect women to be at much greater risk for developing it, which is exactly what we see in the real world. (16)
SIBO Causes Systemic Inflammation
We now know that when these inflammatory chemicals get into the brain, they can directly induce changes in levels of two other chemical messengers believed to be involved in fibromyalgia called glutamate and γ-aminobutyric acid (GABA). (21) People with fibromyalgia have been consistently found to have an imbalance in signals carried by these two chemicals in a specific area of the brain, the insular cortex. (22, 23, 24)
This area is responsible for integrating sensory signals from the skin, muscles and joints of the body, including pain signals (25) and researchers strongly suspect that this imbalance in the insular cortex play a direct role in the pain dysregulation seen in fibromyalgia. (22, 23, 24)
This theory of the development of fibromyalgia is also strongly supported by epidemiological data. Studies consistently find that those with fibromyalgia have marked increases in levels of inflammation and oxidative stress in their bodies, (2, 19, 26) potentially stemming from SIBO.
What to Do if You Have Fibromyalgia
Given all we know about fibromyalgia, here are a few things to do if you want to reduce the symptoms you experience from this disorder:
1. Get Tested for and Treat SIBO
The evidence clearly supports at least getting tested for SIBO if you have been diagnosed with fibromyalgia.
SIBO is usually tested for by measuring the amount of hydrogen and/or methane in your breath over the course of several hours. It’s simple, non-invasive and may be covered by your insurance.
If your SIBO test comes back positive, your doctor may choose to prescribe a course of antibiotics for you which can kill off the bacteria in your small intestine. You can also use antimicrobial herbs to this effect.
SIBO is linked to a variety of medical conditions, so even if it turns out clearing SIBO does not affect your fibromyalgia, it is still something that absolutely should be dealt with.
If you’re interested in learning more about testing for SIBO and using antimicrobial herbs, check out my 8-week Build Your Biome program.
2. Support Healthy Serotonin Production
As discussed above, serotonin is very important when it comes to fibromyalgia. Here are some steps to take that may help support healthy serotonin levels in your brain:
- Eat a diet full of tryptophan-rich foods, such as walnuts, rice, potatoes and dark chocolate (16)
- Avoid foods rich in free sugars which might bind and inhibit tryptophan absorption, such as processed foods made with table sugar or high fructose corn syrup (16, 27)
- Avoid foods containing aspartame, which can make it difficult for tryptophan to get out of your bloodstream and into your brain (16, 27)
- Exercise regularly; physical activity has been shown to boost serotonin production in the brain and ease the symptoms of fibromyalgia (28, 29, 30)
- Get outside; exposure to natural sunlight may boost serotonin production (29)
3. Decrease Inflammation and Oxidative Stress
The clear markers of systemic inflammation and oxidative stress in fibromyalgia also strongly suggest that steps to combat them may be useful in addressing fibromyalgia symptoms, even if determined not to be caused by SIBO.
Steps that may be useful in decreasing inflammation and oxidative stress include:
- Eating a plant-rich diet; plants are rich in antioxidants and anti-inflammatory phytonutrients (27)
- Avoid smoking and cigarette smoke which has been proven to cause oxidative stress throughout the body (31, 32)
- Consider taking a CoQ10 supplement, which is a natural compound known to be depleted by oxidative stress and which has been specifically shown to be helpful in fibromyalgia (27)
If you have fibromyalgia, have you been tested for SIBO? Let me know in the comment section below!