Migrating Motor Complex: Why Snacking is Detrimental to Gut Health

May 10, 2023

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It all began with an apple, the ultimate snack.

The clerics proclaimed that the act doomed humanity, but we didn’t forget the habit.

A 2015 survey from Mintel on Snacking Motivations and Attitudes in the US states that 94% of Americans snack at least once daily, and 50% of adults snack two to three times each day. Additionally, Mintel highlights that in America, regular meals may be replaced soon by more frequent snacks, and Americans feel that anything can now be considered a snack. ¹

This was well over 8 years ago, and the numbers have deteriorated further during the pandemic-induced lockdowns when most of the world found itself stuck inside homes and snacking became a kind of a "lifeline" for most, which is confirmed comprehensively by the State of Snacking survey done by Mondelez International.² The habit also seems to have stuck post-covid.

So why is snacking so dangerous, you might ask? You may think of the usual suspects such as weight gain, obesity, blood sugar imbalances, or tooth decay, but one of the most unfortunate victims of our daily snacking habits happens to be our gut—such a surprise. It turns out that digestion is a complicated operation that includes interaction between multiple organs and systems, resulting in a series of complex processes and sub-processes that eventually culminate in the ultimate alchemy of turning food into energy. One of the most important processes in our digestive tract is the Migrating Motor Complex (MMC), which gets disrupted due to frequent meals, snacks, and other multiple factors. Let us explore together this often unknown but essential process and its major disruptors. So we can all live a much more gut-friendly and healthier life.

The migrating motor complex (MMC) is a series of coordinated contractions of the muscles in the gastrointestinal (GI) tract that occurs during periods of fasting. These contractions are important for the movement of food and debris through the GI tract and are regulated by a complex interplay of hormones, nerves, and neurotransmitters. It serves to clear the stomach and small intestine of residual food and debris, helping to maintain ideal digestive function. The MMC also prevents the accumulation of bacteria and waste material in the lower intestine, which can lead to infections and other complications. The Migrating Motor Complex (MMC) is divided into four distinct phases, each with its own unique pattern of contraction and purpose.

Phase 1

The first phase, known as the quiescent phase, begins shortly after eating and lasts about 90 minutes. There is little or no activity in the GI system during this phase as the body digests and absorbs the previously eaten meal.

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Phase 2

The second phase of the MMC, known as the initiation phase, occurs after the quiescent phase ends. The smooth muscles of the stomach and small intestine begin to tighten in unison during this phase, creating small and irregular waves, driving any residual food and debris toward the large intestine.

Phase 3

The propulsive phase of the MMC is characterized by high-amplitude contractions of the small intestine that transport almost all leftover food and debris toward the large intestine. This phase usually lasts about 20-30 minutes.³

Phase 4

The fourth and final phase of the MMC begins immediately after the propulsive phase. Phase four is a transition phase between phases 1 and 3. During this phase, the contractions in the GI tract slow down and eventually stop, allowing the body to rest and recover before the next phase of the MMC begins. The total time duration for the completion of MMC is estimated to be about 130 minutes. ⁴

The Importance of the Migrating Motor Complex (MMC)

The MMC plays many important functions in our digestive systems. The contractions of the MMC help to mix and move the contents of the GI tract, allowing for the proper breakdown and absorption of nutrients. Without the MMC, food and nutrients would not be properly digested and absorbed into our bodies, leading to malnutrition and other deficiency-related diseases. Furthermore, the MMC is involved in appetite and satiety regulation. The MMC contractions assist in sending messages to the brain suggesting that the stomach is empty and it is time to eat. The body can manage hunger and prevent overeating by adjusting meal intervals with the time and frequency of the MMC. The MMC's role in limiting bacterial overgrowth in the small intestine is also one of its most significant roles. During fasting, the contractions of the MMC serve to eliminate any residual food and debris from the small intestine, preventing germs from growing in this area. If bacterial overgrowth occurs, it may result in a condition known as small intestine bacterial overgrowth (SIBO).⁵ The MMC cycle also keeps other digestive diseases and disorders at bay, such as Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD). The MMC also plays a role in preventing reflux of stomach acid into the esophagus, which can cause symptoms such as heartburn and GERD (gastroesophageal reflux disease). This helps us understand that the MMC is a critical physiological process that ensures the proper function of the gastrointestinal tract, and it is indispensable for a healthy lifestyle to keep it running in ideal condition.

Disruptors

The migrating motor complex (MMC) is a process that is easily susceptible to disruption by a variety of factors. One of the most common disruptors of the MMC is food intake. The motor complexes are activated during periods of fasting, and frequent eating disrupts the process by stimulating the release of certain digestive hormones. These hormones make the muscles of the GI tract relax instead of continuing the MMC contractions. Snacking between meals is one of the main culprits for the disruption in MMC rhythms, keeping appropriate fasting periods between meals of about 4-5 hours can help the process function smoothly. Longer fasting periods of up to 12 hours or more are required for the thorough cleaning of the colon which can be achieved through overnight fasting between dinner and breakfast. The longer fasting periods help the MMC to run multiple times clearing the GI tract completely of any residue. Eating large meals and consuming high-fat or high-protein meals can also disrupt the MMC process and are to be avoided.

All physical systems in our body are psychosomatic, and digestion is no exception. Lifestyle and emotional factors such as stress and anxiety can also disrupt the proper functioning of the MMC. Chronic stress and anxiety can lead to prolonged disruptions of the MMC, which can lead to conditions such as irritable bowel syndrome (IBS). Certain drugs can potentially interfere with the MMC. Opioids and antibiotics are well known to impede GI motility and reduce MMC activity. It is extremely important for all individuals to understand the MMC rhythms and keep them running, ideally to lead a more fulfilling life devoid of any gut issues.

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Indexed References
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A snacking nation: 94% of Americans snack daily. (n.d.). Www.mintel.com. https://www.mintel.com/press-centre/a-snacking-nation-94-of-americans-snack-daily/

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foodnavigator-asia.com. (n.d.). Pandemic snack attack: Rise of work-from-home culture driving snacking trend in Australia - Mondelez report. Foodnavigator-Asia.com. https://www.foodnavigator-asia.com/Article/2021/06/01/Pandemic-snack-attack-Rise-of-work-from-home-culture-driving-snacking-trend-in-Australia-Mondelez-report

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The Migrating Motor Complex. (2019). Colostate.edu. http://www.vivo.colostate.edu/hbooks/pathphys/digestion/stomach/mmcomplex.html
Ma, Z. F., & Lee, Y. Y. (2020, January 1). Chapter 7 - Small intestine anatomy and physiology (S. S. C. Rao, Y. Y. Lee, & U. C. Ghoshal, Eds.). ScienceDirect; Academic Press. https://www.sciencedirect.com/science/article/abs/pii/B9780128130377000078
The Role of the Migrating Motor Complex in IBS and SIBO — Gutivate. (n.d.). Gutivate - IBS & SIBO Nutrition Counseling & Coaching. Retrieved April 26, 2023, from https://gutivate.com/blog/migrating-motor-complex

Other References

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Mintel. (n.d.). A snacking nation: 94% of Americans snack daily. Www.prnewswire.com. Retrieved April 26, 2023, from https://www.prnewswire.com/news-releases/a-snacking-nation-94-of-americans-snack-daily-300111225.html

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Gagliardi, N. (n.d.). The New Way Americans Are Snacking. Forbes. Retrieved April 26, 2023, from https://www.forbes.com/sites/nancygagliardi/2014/10/13/the-new-way-americans-are-snacking/?sh=26dd71ef52e4

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Consumers say snacking is a “lifeline” during pandemic, with 88% doing it more or the same. (n.d.). Food Dive. https://www.fooddive.com/news/consumers-say-snacking-is-a-lifeline-during-pandemic-with-88-doing-it-m/588779/

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Deloose, E., Janssen, P., Depoortere, I., & Tack, J. (2012). The migrating motor complex: control mechanisms and its role in health and disease. Nature Reviews Gastroenterology & Hepatology, 9(5), 271–285. https://doi.org/10.1038/nrgastro.2012.57

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Migrating Motor Complex - an overview | ScienceDirect Topics. (n.d.). Www.sciencedirect.com. https://www.sciencedirect.com/topics/medicine-and-dentistry/migrating-motor-complex

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Deloose, E., & Tack, J. (2016). Redefining the functional roles of the gastrointestinal migrating motor complex and motilin in small bacterial overgrowth and hunger signaling. American Journal of Physiology-Gastrointestinal and Liver Physiology, 310(4), G228–G233. https://doi.org/10.1152/ajpgi.00212.2015

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Hasler, W. L. (2004, January 1). Duodenal Motility (L. R. Johnson, Ed.). ScienceDirect; Elsevier. https://www.sciencedirect.com/science/article/abs/pii/B0123868602001969

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