Migrating motor complex deficiency is seen in 70% of patients who have SIBO, because it creates an environment in the small intestines that is ripe for an overgrowth. An MMC deficiency also contributes to the high relapse rates seen in SIBO patients. Unless the MMC deficiency is addressed, no amount of herbs or pharmaceutical antibiotics will keep the small intestines clear.

So what exactly is the migrating motor complex? The MMC is a cyclical pattern of electromechanical activity that is observed in the smooth muscle of the GI tract between meals. You can think of the MMC as a cleansing wave that sweeps the small intestines clean between meals.

In a healthy individual, these cleansing waves come every 1.5-2 hours, but someone with SIBO has more infrequent MMC activity. With an MMC deficiency, SIBO patients have food, bacteria and waste sitting in their small intestines for longer periods of time. The inefficiency of the MMC will lead to the development of SIBO and if unaddressed, relapse is inevitable.

So, what inhibits the MMC?

I made this handy dandy infographic! And I will give a brief explanation of each one!

MMC function

12 Things that inhibit MMC function

1. High levels of anti-CdtB and anti-vinculin antibodies. 

These are two antibodies that rise following a food poisoning event. When you have food poisoning, your immune system develops antibodies to fight the toxins produced by the micro-organisms that have invaded the body. The toxin that is associated with IBS and SIBO is cytolethal distending toxin or CdtB toxin.

While the antibody helps remove the toxin from the body, it also has a striking resemblance (aka molecular mimicry) to a protein called vinculin that are found in the interstitial cells of Cajal and myoenteric ganglia (bundles of nerve cells). These cells innervate the gut allowing the smooth muscle of the gut to contract.

Shit really hits the fan (pun intended) when your body starts mistaking vinculin as the CdtB toxin. This auto-immune attack of your own vinculin will damage the nerves in the smooth muscle of the GI tract and reduce the ability of the cells to carry out their digestive functions. When these cells that are necessary for producing the MMC between meals atrophy, SIBO is eminent.

Over time the levels of the CdtB toxin should decrease. Repairing the vinculin and nervous function in the gut usually requires prokinetics and vagus nerve exercises.

2. Snacking and Grazing 

The MMC only sweeps the small intestines in periods of fasting between meals. MMC activity shuts down when we eat. By eating snacks or grazing between meals, you may be inhibiting you MMC function even more. Try to space out meals to increase MMC function.

Intermittent fasting can be helpful for some case. Although, some people with hormone issues may want to steer clear of this approach and stick with three meals a day.

3. Stevia

Dr. Pimental has stated that Stevia inhibits MMC function. I know it is a popular choice for many avoiding processed foods, but eating this regularly could do a number on your MMC function. Stick to more natural sweeteners like a little bit of maple syrup or honey if they are well tolerated.

4. Chewing gum

It is not only the sugar alcohols in gum that can cause GI upset. The act of chewing tricks your brain that you are eating and will shut down your MMC. Best to quit gum chewing to restore MMC function.

5. Large intestine pathogens and imbalances 

One of the biggest mistakes I see that many SIBO patients make is failing to address imbalances in the large intestines. Bacteria in the large intestines have been shown to modulate MMC activity in animal studies.

When germ free mice were inoculated with healthy gut bacteria, the intervals between MMC sweeps decreased by 56%! This increase in MMC activity shows that healthy gut bacteria is imperative to produce a robust MMC response.

Later the researchers found that certain bacteria seem to improve the MMC frequency while others reduce it. Bifidobacterium bifidum and Lactobacillus acidophilus have been shown to strengthen MMC activity while Micrococcus luteus and E. coli reduce MMC activity.

If you have dysbiosis with low levels of good MMC strengthening gut bugs, then you are gonna struggle to find long term relief from SIBO. Building a healthy and robust bacterial population in the large intestines needs to be a priority in SIBO treatment.

6. Starving good gut bugs with a low fermentable fiber diet

Long term implementations of low fermentable fiber diets inhibit MMC function by creating large intestine imbalances that I discussed above.

The Low FODMAP diet has been shown to reduce Bifidobacterium. As we mentioned before, Bifido bacteria are associated with increasing the frequency of MMC activity. By lowering these bacteria even further with a low FODMAP diet, you may be decreasing your MMC even further.

7. Weak vagus nerve function

Vagus nerve signals the MMC to fire into the nervous system of the gut. If this nerve is weak and not functioning properly, then you may need to strengthen it.

Being in a chronic state of stress can inhibit MMC by reducing the activation of the vagus nerve. Building vagal tone is a great way to decrease stress and increase MMC activity. Check out this article about how to repair the brain-gut axis to learn more!

8. Brain injury or neuroinflammation 

If you have a history of concussions or even have developed signs of neurodegeneration, you may need to address inflammation in the brain to boost MMC function. MMC activity is an autonomic function that is controlled by the brain. If the brain is inflamed, the signaling to the gut will be suboptimal.

The real kicker is that chronic gut issues lead to brain issues. Datis Kharrazian, a brain and gut health expert) always says that if your gut is on fire, so is your brain. Many SIBO patients experience brain issues like poor concentration, memory decline, handwriting decline and brain fog.

Showing your brain some extra love and support during SIBO treatment can help mitigate some of these symptoms. Resveratrol, omega 3s, curcumin and ginger are all great natural remedies to help turn off inflammation in the brain.

9. Blood Sugar Swings  

Many people who struggle with blood sugar issue are also going to have a weaker MMC. High blood sugar also known as hyperglycemia damages the nerves in the GI tract, which reduces MMC function.

You don’t have to have diabetes or prediabetes for blood sugar issues to be a problem. Many people with hormone imbalances (especially cortisol and thyroid) will have blood sugar swings. SIBO and large intestine dysbiosis can also cause metabolic endotoxemia that leads to blood sugar instability.

I had pretty bad blood sugar swings when my SIBO and hormones were out of whack. I found it helpful to use a glucose meter to track how my body was responding to carbohydrates. This tracking allowed me to determine which carbs worked well for my body and established threshold amounts.

10. Cortisol dysregulation (aka HPA axis dysfunction) and chronic stress

High cortisol levels wreak havoc on the gut. One of the big reasons stress is so bad for SIBO patients is that it reduces MMC activity. Employing stress management techniques should be a top priority during SIBO treatment. You can check out this recent post were I discuss the SIBO-stress connection.

11. Thyroid Dysfunction 

I have talked extensively about the SIBO-thyroid connection. About 50% of hypothyroid patients have SIBO. A big reason for this strong connection is that hypothyroidism will modulates the enteric nervous system in the gut leading to reduced smooth muscle and MMC function in the small intestines.

SIBO can also lead to hypothyroidism by increasing inflammation and reducing conversion of thyroid hormones into their active form. Eliminating the inflammation from SIBO should boost thyroid function.

12. Myofunctional issues like poor tongue posture 

Myofunctional issues can create huge problems for people with SIBO. If you are someone who breathes through your mouth (even at night) and your tongue does not rest at the roof of your mouth, then you may have developed a lazy vagus nerve. Therefore, myofunctional issues cause MMC deficiency by failing to stimulate the vagus nerve on a regular basis.

Myofunctional issues are not discussed very frequently, but can leave your body stuck in a sympathetic or fight or flight state that will raise stress hormones and derail digestion in many different ways.

Myofunctional therapy can be a game changer for certain individuals with GI dysfunction and poor tongue posture! To learn more about the tongue-gut connection you can check out this interview I did with my friend Sarah Hornsby who is an amazing myofunctional therapist.

Bottom Line: 

Try to avoid MMC inhibitors!

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  • Hi Amy! Once again, thank you for a great post. 🙂 I know this question must sound totally annoying to someone who has struggled with SIBO and knows how real it is but I have to ask: is there enough scientific evidence to prove SIBO is real? I’m asking because my GP had no idea what SIBO even is and seemed to think it was a bunch of quackery, as well as the functional stool testing I had done. I found plenty of studies about SIBO and to me it seems very real but she said it sounds far fetched that bacteria in the small intestine could be causing symptoms. What do you think?

    • Hi Sini! Thanks so much for your question! Yes, SIBO is definitely real. Personally, I feel that it may be overdiagnosed since breath testing can lack accuracy and symptoms often mimic large intestinal issues or SIFO. But, there is so much research on the gold standard of testing, which is duodenal aspirate (or culture) taken directly from the small intestines, which shows a correlation in GI symptoms and overgrowth of bacteria in the small intestines. Plus, antibiotics have been shown to reduce symptoms. Your GI doc should know what it is and shouldn’t be dismissive of your concerns. You should find some research articles to send of bring in the next time you see him to support the fact that SIBO is real and should be ruled out if you are having tons of symptoms.

      • Hi Amy, thanks for the reply. I have found some articles and will be sending them for my doc to see. I’m trying to figure out the tests I should have done, I had a GI effects stool analysis taken and I’m waiting for the results. That’s where I’m starting from, then later possible SIBO testing and gastric emptying scan. Do you know anything about the relationship between gastroparesis and SIBO? I’ve understood delayed gastric emptying is different from MMC dysfunction, is this correct? Do you know what could cause gastroparesis? Btw, your knowledge on the subject makes me feel much safer haha.

  • Great post, thanks! Really like the infographic. Haven’t heard much about myofunctional issues being connected with SIBO – I will have to look into that more!