Bloating, Gut Health, and the Migrating Motor Complex

If you have found yourself snacking more these past few months you are definitely not alone.

And I am not here to tell you to stop, or that it's a bad thing to do. My approach to nutrition is not about restriction, deprivation, or stressing about how much you are eating. 

However, I do want to talk about the migrating motor complex (MMC) and its role in maintaining healthy gut function.

What is MMC? Migrating Motor Complex is a sequence of muscle contractions throughout the digestive system that acts as a 'cleaning wave' to help keep contents moving along. (1,3)

These cleaning waves occur after ~ 90 mins of fasting. The majority of the cleaning waves happen at night while we are asleep, and for many people this will be sufficient enough to help maintain a healthy, balanced environment in the digestive tract. For others, it may be beneficial to space out food intake to allow for a couple cleaning waves to occur between meals throughout the day as well.

If you are someone that experiences bloating or other digestive issues, it may be worth trying out a few different options when it comes to supporting the MMC.

Whether or not snacking in between meals is a new habit or something you have always done, try spacing out your snacks/meals by about 4 hours, and only having water in between. 

To help maintain this eating schedule, it is important to eat enough at each meal, and for the meals to include plant based proteins, healthy fats, and complex carbohydrates. 

This type of eating schedule won't be suitable for everyone, and it may be difficult for athletes to get the calories they need by just eating 3 meals a day.

If you try it and feel it doesn't work for you, you could try instead to increase the length of time you are not eating between dinner and breakfast the next day in order to help increase the number of cleaning waves that happen at night (aim for a 12-13 hour window). Then, throughout the day, you may be able to have more frequent meals (i.e. every 2.5-3.5 hours) since you'll likely be increasing the cleaning waves that happen between dinner and breakfast the next day. 

Again, everyone is different so it will be important to figure out what works for you. 

Obviously, this alone may not solve all of your digestive issues, but it is a piece of the puzzle that's worth considering when dealing with bloating, indigestion, heartburn, and other symptoms associated with SIBO or IBS. 

There are multiple underlying factors that can contribute to decreased activity of the MMC:
​

• Chronic stress: as this may decrease the tone/strength of the vagus nerve (i.e. a low vagal tone) - which then decreases MMC activity (1,3,7); high levels of the stress hormone cortisol may also interfere with MMC activity
• Constant snacking/eating: this turns off the next MMC (1,3)
• Gut dysbiosis: certain strains of gut bacteria decrease the activity of the MMC, while other strains are supportive (6,8,10) (getting enough fibre from a highly diverse range of plant foods is key to supporting proper gut bacterial balance); gut dysbiosis also leads to an increase in methane and hydrogen sulphide gases within the colon - these gases decrease bowel transit time and decrease the muscle contractions involved with the MMC (4,5,10) (hydrogen sulphide is one of the gases that increases with increased intake of animal protein - see my protein article HERE)
• Thyroid dysfunction: low thyroid function may lead to decreased MMC activity (13)
• Brain injury or inflammation: as this may affect proper functioning of the vagus nerve
• Low fibre diet: a low fibre diet means there is a low production of Short Chain Fatty Acids (SCFAs), SCFAs play an important role in inflammation, brain health, & vagal tone (7,10)
• Artificial sweeteners and natural alternatives like stevia: these indirectly affect the MMC by altering the gut microbiome (11)

MMC & the Vagus Nerve:

The health of your vagus nerve can sometimes be the missing piece of the puzzle when it comes to examining the root cause of gut imbalances. Work with your doctor to determine whether or not your vagus nerve or MMC may be involved with your digestive symptoms.

The vagus nerve is a 2-way highway of communication between the gut and the brain. (7) And they influence each other in both directions. Low vagal tone can lead to gut disfunction and dysbiosis, and dysbiosis can lead to low vagal tone. (10)

There are many factors when it comes to the involvement of the vagus nerve with digestive health. Low vagal tone may be involved with:

• Low stomach acid production
• Low digestive enzyme production
• Decreased motility, decreased MMC (1,3)
• Decreased blood flow (oxygen/nutrients) to the digestive organs

There are a number of simple ways to support the health of the vagus nerve (12):

• Gargling a couple of times a day 
• Deep breathing
• Ending your shower with cold water
• Yoga, meditation
• Stress management

MMC & IBS/SIBO:

There are often gut motility issues and MMC irregularities involved with Irritable Bowel Syndrome (IBS) and Small Intestinal Bacterial Overgrowth (SIBO). (9)

"The MMC has been considered an “intestinal housekeeper” that prevents SIBO" (9)

• MMC is responsible for clearing out bacteria that may have made its way into the small intestine (6,9)
• MMC helps prevent backwards movement of bacteria from the large intestine to the small intestine via an incompletely closed ileocecal valve (9)
• Many people with IBS test positive for SIBO
• There is decreased MMC activity in people with SIBO 
• Gut motility and MMC issues are involved with relapse of SIBO after antibiotic treatment

Your doctor may include short-term use of prokinetics after SIBO treatment to help prevent relapse (prokinetics stimulate gut motility and MMC - however it is still important to try to figure out the underlying reason(s) for the gut motility/MMC issues as prokinetics are not always a suitable long-term solution)

It is important to treat SIBO and determine the underlying causes of SIBO (2,9), IBS and other digestive issues since SIBO and other gut imbalances eventually lead to nutrient deficiencies and other chronic health issues.

There are many possible underlying causes when it comes to digestive issues, and the MMC and health of the vagus nerve is only one area of possibility. However, it is one that is important to talk to your doctor about, especially when many other factors have already been ruled out as a cause, or have been addressed in your treatment protocol.

1. https://www.ncbi.nlm.nih.gov/pubmed/22450306
2. https://www.tandfonline.com/doi/abs/10.1586/17474124.2016.1110017
3. https://akjournals.com/view/journals/2060/104/2/article-p97.xml
4. https://www.ncbi.nlm.nih.gov/pubmed/19919833/
5. https://www.ncbi.nlm.nih.gov/pubmed/16293652/
6.https://journals.lww.com/ajg/Abstract/2005/11000/Interactions_Between_Commensal_Bacteria_and_Gut.31.aspx
7. https://www.ncbi.nlm.nih.gov/pubmed/26364692
8. https://www.ncbi.nlm.nih.gov/pubmed/11171619?log$=activity
9. https://journals.physiology.org/doi/full/10.1152/ajpgi.00212.2015
10. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112865/#B82
11.https://www.researchgate.net/profile/Brenda_Lorena_Jimenez_Cruz/publication/327179772_Association_of_Natural_and_Artificial_Nonnutritive_Sweeteners_on_Gastrointestinal_Disorders_A_Narrative_Review/links/5b969064a6fdccfd543b541c/Association-of-Natural-and-Artificial-Nonnutritive-Sweeteners-on-Gastrointestinal-Disorders-A-Narrative-Review.pdf
12. https://www.sciencedirect.com/science/article/abs/pii/S1525505016305625
13. https://link.springer.com/article/10.1007/s40618-016-0594-6

Book 15 Min Discovery Call