SIBO & the MMC – Part II: Influences

This is part two of a five part series. The parts are:

  1. What is the MMC and why we care
  2. What Influences the MMC
  3. When things go bad with the MMC
  4. Healing with drugs and herbs
  5. Healing with lifestyle measures


MMC stands for Migrating Motor Complex.  The MMC is the ‘housekeeper’ of your gastrointestinal tract. It cleans up the stuff that should not be there, moving stuff along when it is time for it to move along.  But some people have poor housekeepers and then things go wrong, resulting in Small Intestine Bacterial Overgrowth (SIBO) and other horrors.

What influences the MMC?

You knew it was coming, yes our hero of the blog the Vagus Nerve (you can find more about him here)  has a role in the MMC (Miyano, Sakata et al. 2013).  The finer details are a little hazy.

Motilin: is a polypeptide involved in the MMC, especially in dogs and humans.  Its role is species dependent and isn’t involved in rats.  If rats are in the picture research tends to move slower (a tragic truth for both humans and the poor rats).

Ghrelin: is from the same peptide family as Motilin and is shown to create premature phase III contractions.  Motilin and Ghrelin work together to support the MMC.  If rats are given a vagotomy – the ghrelin-induced contractions are abolished.   A vagotomy is the removal of part of the vagus nerve.  See what I meant about the poor research rats.

Serotonin (5-HT): seems to influence the MMC.  Intravenous administration of it increases phase III, but not so by a feeding tube (Deloose, Janssen et al. 2012).  What happens with pills no one is telling me.

The gut microbiome:  Like everything with the dam gut microbiome what/when/how it influences the MMC seems a bit too complex for us to unpick just now.

What interferes with the MMC?

Obesity:  Yep fat folks are blamed for everything to do with their own health.  Well here it goes again, Phase III does not seem to work as well is obese people as in healthy controls.

Age: Poor old people seem to be more likely to have a dodgey MMC.

Bloating: It seems maybe bloating messes it up somewhat (Deloose, Janssen et al. 2012).

Eating: Yes eating is a problem – but so is not eating as anorexia nervosa messes with it too.  However, the eating thing seems more than a little complex.  When Pigs, rabbits and sheep are fed ‘at leisure’ the MMC is not interrupted, but those that were fed once or twice a day, eating did interrupt the MMC. (Deloose, Janssen et al. 2012).

Stress: One study stressed out health peeps and noticed changes in gut motility (Huerta-Franco, Vargas-Luna et al. 2012).  So what about us poor spoonie types who are often wound up like springs and stuck in the ‘fight or flight’?  Also, an older study showed changes to the MMC in stressed dogs (Gue, Peeters et al. 1989).  Healthy people, dogs? it’s everywhere…we are doomed.

Alcohol:  Here is a scary quote for those of us that love a drink.  “The Gastrointestinal tract is one of the most affected systems by alcohol consumption” (Grad, Abenavoli et al. 2016).  Exactly how is not straight forward, with different alcohol amounts and strengths working differently on the gut.  So if I drink the right drink in the right amounts at the right time it is medicine yes? No. Probably not. Dam.

Drugs/Smokes and other evils:  Goes without saying really.  But wait, low doses of morphine speed up the MMC.  Now we are talking.  Don’t try this at home folks.

Coming up

Now we know a bit about what the MMC is, why it matters and what things make it unhappy.

The story next week will take a turn for the worst – we will look at what happens when the MMC goes bad.  Very Bad. Be prepared.


I am not a doctor, I am also a spoonie* and one of my challenges is Small Intestine Bacterial Overgrowth (SIBO).  SIBO tends to reoccur after treatment in many cases.   So I am putting my research skills (I am a middle aged PhD student) into finding out what I can do to help improve my MMC and sharing that with others who also might have an unhappy MMC.  However given my area is not medical research some of this is pretty tough going (because academics never learnt the ‘write for a 10-year-old’ thing, actually some of them never learnt the ‘write for anyone at all’ thing).


Deloose, E., et al. (2012). “The migrating motor complex: control mechanisms and its role in health and disease.” Nature Reviews Gastroenterology and Hepatology 9(5): 271-285.

Grad, S., et al. (2016). “The Effect of Alcohol on Gastrointestinal Motility.” Reviews on Recent Clinical Trials 11(3): 191-195.

Gue, M., et al. (1989). “Stress-induced changes in gastric emptying, postprandial motility, and plasma gut hormone levels in dogs.” Gastroenterology 97(5): 1101-1107.

Huerta-Franco, M. R., et al. (2012). “Effect of psychological stress on gastric motility assessed by electrical bio-impedance.” World J Gastroenterol 18(36): 5027-5033.

Miyano, Y., et al. (2013). “The role of the vagus nerve in the migrating motor complex and ghrelin-and motilin-induced gastric contraction in suncus.” PloS one 8(5): e64777.





Post Tagged with , ,

Leave a Reply

Your email address will not be published. Required fields are marked *