GI Motility Part 1 – What it is, why it matters and what causes problems

What is motility?

Motility of the gastrointestinal tract or gut is defined as contractions of the smooth muscle of the digestive system, and the transit of the contents within it. Smooth muscle is a type of muscle tissue used by various systems of the body to apply pressure to vessels and organs. These contractions are known as peristalsis.

If nerves or muscles in any part of the digestive tract don’t function with normal strength and coordination, motility problems develop.

More specifically, motility includes

The movement of food down the oesophagus and into the stomach
Supporting the breakdown of food in the stomach
The movement of this broken down food from the stomach into the small intestine (duodenum) in wave type motions
Segments of the small intestine or bowel contracting and relaxing to allow sufficient time for the digestion and absorption of nutrients
The migrating myoelectric (motor) complex (MMC), which is a pattern of electrical activity that occurs during fasting e.g. overnight or between meals, and sweeps through the small intestine to ‘clean’ it
In the colon with the recycling and reabsorption of the water and electrolytes (minerals) needed to hydrate the rest of digestion

If smooth muscle contractions are unrestrained or uncoordinated, they’re unable to produce useful movements or motility.

Signs and symptoms of motility problems

Possible signs and symptoms of motility issues include

Constipation
Diarrhoea
Heartburn
Bile reflux
Hernias
Difficulty swallowing
The need for coffee, magnesium or stool softeners to have a bowel movement
A negative reaction to dietary fibres
Gas, bloating, cramps, vomiting
Gastroparesis
Various other gut disorders

The consequences of poor motility

Without good motility these health problems can develop

Gut infections or overgrowths of yeast, bacteria, parasites, viruses
SIBO (small intestinal bacterial overgrowth)
A lack of short-chain fatty acid growth to feed our gut cells
Low microbiome diversity necessary for good general health
Immune issues
Hormone and neurotransmitter production issues
Nutrient deficiencies
Detoxification issues

What causes gut motility problems?

Motility problems with can be due to either

A problem within the smooth muscle that controls gut contractions or peristalsis
A problem with the nerves or hormones that control these muscle contractions

You may have noticed a chicken and egg scenario here. For example, poor gut motility can create brain degeneration, which can lead to worsening motility. Similarly, metabolic or endocrine (hormonal) problems can lead to poor motility, but they can in part be due to poor gut health. While research on the gut and motility has advanced leaps and bounds in the last 15 years, there’s still a lot to learn.

More specific causes include

Dehydration
Diets low in fibre, and/or high in refined carbs and processed fats
Gut infections including bacterial, yeast, parasitic, viral
Drugs
Laxatives
Blood sugar dysregulation
Gut-brain axis issues
Neurodegenerative disorders
High methane release (caused by dysbiosis with gut infections and SIBO)
Low nutrient diet
Chronic stress

Examples of secondary causes of motility problems include

Diabetes
Lupus
Ehlers-Danlos Syndrome (EDS)
Neurological Disorders
Parkinson’s
Vagal injury
Multiple Sclerosis
Thyroid disorders

The role of the brain

By now you may have gathered that the brain plays a vital role in gastrointestinal function.

Importantly, it controls the movement of food through the intestines, or motility, via the vagus nerve. Through this nerve (the vagus complex and the vagus nuclei) that runs from the base of the brain to the gut, the brain is able to release digestive enzymes to break down food, regulate blood flow carrying nutrients important for gut health, and controls contraction and intestinal motility.

When the brain ages, degenerates or becomes impaired, however, the activation of the brainstem is hindered through a lack of output or stimulation (like any muscle when it isn’t exercised). This can impair the vagus nerve, which may cause poor gut motility and constipation.