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  • Taylor Richter, RDN, LD

The Migrating Motor Complex... Whatever that Means!

Ever wondered what goes on inside your digestive system when you're not eating? It's not something most of us think about, but understanding what happens after a meal is just as vital as choosing the right foods to eat. Our body orchestrates the movement of food through the intestines using a process known as the migrating motor complex (MMC). This intricate dance of contractions and smooth muscle movements is key to proper digestion and waste elimination. In this blog post, we'll delve into the details of the migrating motor complex, exploring its phases and its crucial role in maintaining a healthy digestive system (2).


Understanding the Basics

The migrating motor complex is a rhythmic pattern of coordinated contractions in the smooth muscles of the gastrointestinal (GI) tract during the fasting state (1, 3). This essential process supports various digestive functions, including the movement of undigested food, debris, and bacteria through the digestive system. It's particularly active between meals, during periods of fasting, and while we sleep. The process kicks in after about 90 minutes of fasting, running its course unless interrupted by ingesting food. So, it's essential to be mindful of constant snacking or consuming sugary drinks, as they can disrupt this cycle.


Phases of the Migrating Motor Complex

The MMC unfolds in three distinct phases, spanning approximately 130 minutes in total. Each phase serves a specific purpose in the digestive journey (1):


Phase I - Quiescence (Resting Phase):

  • Duration: 30-60 minutes

  • This initial phase, occurring between meals, witnesses reduced smooth muscle activity in the GI tract.

  • Its purpose is to allow the digestive system to rest and recover, preparing for the next meal by clearing any residual debris and bacteria.

Phase II - Irregular Contractions (Activity Phase):

  • Duration: 20-40 minutes

  • Characterized by irregular contractions, this phase involves sweeping movements that push remaining content in the digestive tract toward the large intestine.

  • Crucial for efficiently clearing undigested particles and bacteria from the digestive system.

Phase III - Coordinated Contractions (Cleansing Phase):

  • Duration: 10-20 minutes

  • The final phase is marked by powerful, coordinated contractions of the smooth muscles.

  • These contractions ensure a thorough cleansing of the digestive tract by pushing any remaining material into the colon.


Significance in Gastrointestinal Health

The migrating motor complex is indispensable for maintaining the health and proper functioning of the GI tract. Key aspects of its significance include:

  • Preventing bacterial overgrowth: By clearing debris and bacteria, the MMC helps prevent bacterial overgrowth, averting potential digestive issues.

  • Ensuring nutrient absorption: Efficient movement of contents through the digestive tract ensures effective nutrient absorption in the small intestine.

  • Preventing constipation: Regular MMC contractions contribute to the prevention of constipation by promoting the movement of waste toward the colon.

  • Supporting overall gut health: A well-functioning MMC is crucial for maintaining a balanced and healthy gut environment, contributing to overall digestive well-being.


Disorders Related to Migrating Motor Complex Dysfunction

Dysfunction of the migrating motor complex can lead to various digestive disorders. Conditions such as gastroparesis, where there is delayed gastric emptying, and small intestinal bacterial overgrowth (SIBO), characterized by an abnormal increase in bacteria in the small intestine, can be associated with MMC dysfunction (4).


Factors That Interrupt the MMC

Modern diets often involve habits that can disrupt the natural rhythm of the migrating motor complex. Some common dietary practices include:

  • Snacking & grazing: Frequent snacking and grazing can interrupt the fasting state required for the initiation of the MMC.

  • Flavored beverages: Even seemingly innocuous choices like flavored beverages, including non-caloric sparkling waters, may disrupt the intricate cycle of the MMC.

  • Sweetened beverages between meals: Consuming sweetened coffee and tea between meals can also interfere with the proper functioning of the migrating motor complex.


How Can We Support Our MMC?

We can promote a well-regulated MMC, contributing to optimal digestive health and overall well-being. Try some of these strategies to promote healthy motility:

  • Meal spacing: Allowing 90 minutes to 5 hours (300 minutes) between meals provides the necessary fasting period for the MMC to initiate and complete its cycles. Three to four hours between meals is often a sweet spot for most people.

  • Avoiding caloric or sweet-tasting beverages: Steering clear of caloric or sweet-tasting beverages between meals is crucial. This includes flavored drinks that might disrupt the MMC process. We recommend sticking with herbal tea and water between meals.

  • 12-Hour overnight fast: Implementing a 12-hour overnight fast is beneficial. This extended fasting period supports the cleansing and restorative actions of the MMC.


Conclusion

In conclusion, the migrating motor complex is a sophisticated and indispensable process that ensures the smooth functioning of the gastrointestinal tract. Its cyclic nature and coordinated contractions play a pivotal role in maintaining digestive health, preventing bacterial overgrowth, and supporting nutrient absorption. Ongoing research holds promise for developing targeted therapies for digestive disorders linked to MMC dysfunction.


Resources

  1. Deloose E, Janssen P, Depoortere I, Tack J. The migrating motor complex: control mechanisms and its role in health and disease. Nat Rev Gastroenterol Hepatol. 2012 Mar 27;9(5):271-85. doi: 10.1038/nrgastro.2012.57. PMID: 22450306.

  2. “Migrating Motor Complex.” Migrating Motor Complex - an Overview | ScienceDirect Topics, 2020, www.sciencedirect.com/topics/medicine-and-dentistry/migrating-motor-complex.

  3. Rao, S. S., Lee, Y. Y., & Ghoshal, U. C. (2020). Clinical and basic Neurogastroenterology and motility. Academic Press.

  4. Salem, Ahmed, and Bandi Chander Ronald. “Small Intestinal Bacterial Overgrowth.” ResearchGate, 2014, www.researchgate.net/profile/Ahmed_Salem44/publication/269994398_Small_Intestinal_Bacterial_Overgrowth_SIBO/links/549d85860cf2b803713a783f.pdf.

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