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You might never have heard of it, but your Migrating Motor Complex (MMC) is super important. It’s an impulse that moves through your small intestine keeping it clean and healthy. You really need to be aware of this little known biological process if you have IBS or SIBO. When it’s damaged or slowed you could be more at risk of getting small intestine bacterial overgrowth (SIBO). 

When I’m working with my IBS and SIBO clients I find supporting the MMC one of the most important things that help create a strong and healthy digestion. Let’s find out more about this critical part of your digestion.

You’ll find some tips on improving your MMC at the end of this article. 

How does the Migrating Motor Complex (MMC) work?

There are four phases of the MMC. These all have a different strength and frequency of the sweeping motion through the gut. The migrating motor complex clears away bits of old food, bacteria that shouldn’t be there, and dead cells that need to be sloughed off in your gut. 

In healthy people, this process happens around 90 minutes after eating. It normally takes around 1.5-3 hours to complete. But, in people with SIBO this process may be less frequent or take longer which can allow the build up of bacteria.  In one study 86% of people who had an abnormal MMC also had an overgrowth of bacteria in the duodenum.

The MMC mostly starts in your stomach, and the upper part of your small intestine. It can only start if you haven’t eaten for around 90 minutes. Any new food entering your stomach will kick start digestive hormones which put a stop to your internal cleaner.  

The migrating motor complex is controlled by the Interstitial Cells of Cajal in your digestive tract. These are cells which link the smooth muscle of your intestines (which help move contents through your gut), to the nervous system. 

These nerves can become damaged through high stress, nervous system conditions, local inflammation in the gut, or physical changes due to injury or surgery. 

White plate on a wooden table. On the plate are numbers 12,, 3, 6, 9 and some clock hands. Some nuts and fruit are distributed on the plate between the clock hands, leaving a portion blank.

What turns your migrating motor complex off? 

As I mentioned above, any kind of food entering your system can pause the MMC. The main stop signals on your MMC are:

  1. Eating – Whenever you eat food your MMC will pause for around 1.5-2 hours. After this food has moved through your digestion it will attempt to start again. If you’re constantly grazing you can see how the MMC might never get all the way through its work
  2. Stress – Any kind of psychological or physiological stress can affect your migrating motor complex. This is down to blood flow being directed to your fight or flight response to ready your for action in times of danger. 
  3. Downing a huge glass of water could trigger your stretch receptors in your stomach tell your brain a large meal has arrived. This could potentially turn off your MMC. Even though you’ve got no calories coming in by just drinking water, for some people with a sensitive digestion the stretch receptor message to your brain could be enough to slow or stop the MMC.
  4. Medication e.g. – opioid pain killers these are known to slow our digestion and motility, and can cause constipation.

What about non-nutritive sweeteners and the MMC? 

If we know that calories stop the progress of the MMC, what about calorie free sweeteners?

Well, there is mixed research about whether artificial sweeteners affect your migrating motor complex. Some studies have shown that artificial sweeteners won’t affect your MMC. However, the results might depend on the type of sweetener being tested. 

  • Ace-K -Motilin is one of the hormones that propels the MMC impulse through the small intestine. Researchers in 2018 found that Acesulfane K (Ace-K) didn’t slow production of motilin in healthy people. They compared whether the MMC was affected when participants drank glucose, fructose or Ace-K solutions and couldn’t see a difference. 
  • Sucralose is the most studied artificial sweetener and is known to increase hormones and peptides like GLP-1, gastric inhibitory polypeptide (GIP), Peptide YY (PYY), and cholecystokinin (CCK). These hormones are known to slow the MMC, but studies in humans haven’t been able to show a link. People were given sucralose to drink and it didn’t cause the release of their digestive hormones. 
  • Stevia – I’ve seen some discussion on social media and blog posts about stevia stopping the MMC but I can’t find any scientific papers which show there is a correlation or causation. If you’re worried about your MMC you might want to avoid stevia in large doses. 
  • Aspartame – Studies have shown that an intragastric infusion (going straight to the stomach with no taste receptor involvement) didn’t stimulate gastric hormones in the same way sugar solutions would. Of course when you drink or taste aspartame you do get a sweet taste, which could alter the reactions.

Health conditions which can affect your MMC

You may have non-digestive conditions which affect your gut motility. Some of the conditions could include:

  • If you’ve had a previous incidence of food poisoning this could affect your MMC – read more about this on my SIBO page
  • Traumatic brain injury – whiplash, concussion, falling from a bike / horse can damage your nervous system resulting in slowed MMC
  • Antibiotics can change your gut bacteria and may affect your MMC. In fact, some bacteria are known to improve the MMC. 
  • Genetics – does it run in your family? Unfortunately some people are just born with genetic mutations which affect the speed of motility. 
  • Diabetes – Blood sugar issues can play havoc with your digestion as well as your nervous system, brain health and energy. People with diabetes might find they have slow gastric emptying due to insulin levels which can affect the MMC. 
  • Ehlers Danlos – this is a condition where your connective tissues and smooth muscles, including your gut, can be looser and slower. This could result in a slower MMC
  • Hypothyroidism – if your thyroid doesn’t work properly it can slow all kinds of processes in the body. So this means hypothyroidism might show up as signs like feeling cold, inability to lose weight, hair loss, brain fog and hormone issues. 
  • If you have Parkinson’s disease you may also experience motility issues, and Parkinson’s is associated with constipation. 
White napkin and piece of white bread on a white plate with a fork. Next to the plate is a glass of water.

How to fix your MMC

There are some quick wins, and longer term strategies which will help resolve issues with your MMC.

Meal timing

Above all, you want to ensure there are some spaces between your meals to allow the MMC to work.

  1. I suggest aiming for a 12 hour fast overnight. This could be finishing your meal around 7pm, and then eating breakfast at 7am. You don’t want to have any extra calories in this time, only water or herb tea. Of course if you’re super hungry, you need to eat, and I’d rather look at the content of your meals to ensure you’re eating enough protein, healthy fats and fibre before limiting any energy intake. However, allowing a break for the MMC to work overnight is one of the key things you can do to help prevent SIBO.
  2. Aim for some spacing in between meals to help rest your digestion. Basically this means not grazing and nibbling on food in between meals. If you need to snack, aim for just one snack in between your main meals.
Vagus nerve support

The vagus nerve is the connection between the gut and the brain. We can help this link to our brain by stimulating the vagus nerve.  Some things that reportedly help the vagus nerve include

  • Cold water swimming or cold water showers – this acute cold exposure is said to improve the vagus nerve.
  • laughing – this can release tension, as well as stimulate the nerves running from your digestive tract to your brain.
  • humming, chanting or singing – this tones up the muscles in the throat and stimulates the nerves, as well as potentially lengthening the breath
  • Deep breathing – this helps tell your brain you are safe, and could help calm your body, reducing stress
Prokinetics

You can take supplements and medication to stimulate an underactive MMC. Ginger is a natural prokinetic, but you might also want to speak to your doctor about medical management which could include low doses of Prucalopride, Erythromycin or Naltrexone.

Meditation and stress management

Building in time to relax and bring down your stress levels is a very effective way to improve digestive issues. You can start with just 5-10 minutes of deep breathing.

I often recommend following a guided meditation for people who are new to sitting still, it doesn’t come easily to me, and I personally find it much easier with some reminders to come back to focus. There are several apps and websites like Calm or Headspace which update their guided relaxations daily.

Where to start with an underactive MMC

If you are worried about your migrating motor complex and it’s possible impact on your digestion then you can either start with some of the suggested actions above, or get in touch with me for some personalised nutrition advice.

Hi I'm Anna Mapson, registered Nutritional Therapist.

I help people with IBS and SIBO get control of unpredictable gut symptoms to find long term relief from painful and embarrassing IBS without restrictive dieting.

I can help you to:

  • understand your digestion better, so you recognise your triggers
  • eat a well balanced diet, with tasty meals that are simple to prepare
  • develop better digestion and more energy

Find more about my 3 month 1:1 Gut Reset programme

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