The role of sleep in digestion 

Sleep plays a significant role in digestion, although it may not be immediately apparent. The connection between sleep and digestion is complex and multifaceted, involving various physiological processes. Sleep is regulated by the circadian rhythm, also known as the body clock. The digestive system is also controlled by the circadian rhythm, which is why individuals often feel hungry at the same time each day.  

Prefer to listen? Click below

Rest and restoration 

Sleep is essential for the body to repair, rejuvenate, and reset. The deep stages of sleep are particularly vital.  During this time, the organs, tissues, and cells that make up the digestive system can not only take a rest but also undergo repair. During deep sleep, the body prioritises cellular repair and growth. This includes repairing the cells lining the digestive tract, which are subject to wear and tear due to constant exposure to food particles and digestive juices. Deep sleep allows these cells to regenerate, thereby maintaining the integrity of the gastrointestinal lining and improving digestion. 

Deep sleep helps strengthen the immune system, which is vital for the digestive system as it has its specialised immune cells that are activated by the beneficial bacteria in the gut. These immune cells protect the gut and digestive system against harmful microbes.  

The organs of the digestive system play a crucial role in the detoxification process by helping to eliminate waste and harmful substances. Deep sleep supports this by enabling the liver and kidneys to function more efficiently.  

Gut Motility 

A crucial aspect of digestion is the efficient movement of food and waste through the digestive tract. This process, known as gut motility, undergoes slight changes during sleep. During sleep, whether deep or light sleep, the speed of gut motility is significantly reduced. This slowdown is a necessary adaptation during which the digestive system conserves energy, which is redirected towards the repair of digestive tissues. This enables digestion to be more efficient during waking hours.  

The migrating motor complex is a pattern of contractions that occurs in cycles when an individual is not eating. This includes periods of deliberate fasting and sleep, during which fasting occurs automatically. This cycle is an essential aspect of gut motility that sweeps food particles and debris that remain in the digestive system. This cleaning of the digestive tract helps reduce the likelihood of bacterial overgrowth and maintains a healthy gut environment. The migrating motor complex is most active overnight when the individual is both fasting and asleep. This highlights the importance of sleep for the overall health of the digestive system.  

As you wake up in the morning, gut motility gradually increases. This prepares the digestive system to process and digest food effectively. It can also trigger the first bowel movement of the day, showing that the relationship between sleep and gut motility is a finely tuned process.  

Hormone Regulation 

Ghrelin stimulates the appetite and is, therefore, often referred to as the hunger hormone. On the opposite side of the coin is leptin, which signals to the brain that the stomach is full, thereby stopping the individual from eating more. For this reason, this hormone is known as the satiety hormone. These hormones can be negatively impacted by insufficient sleep.  

Even one disturbed night’s sleep can affect digestion by causing an increase in ghrelin. This not only increases appetite but can also lead to cravings for carbohydrates. This feeling is often described as ‘hangry’. To make matters worse, leptin levels decrease after poor sleep, disrupting the signal that tells the body to stop eating.  This creates a perfect storm with the individual not only overeating but also potentially eating unhealthy foods, along with not knowing when to stop eating. The occasional poor night's sleep does not cause too much damage. However, suppose the individual suffers from chronic insomnia.

In that case, it can cause inflammation in the gut. This inflammation can lead to serious digestive issues and other health problems. It may contribute to liver disorders and gastroesophageal reflux disease. It can also lead to inflammatory bowel disease, colorectal cancer, and weight gain.

Disrupted sleep 

When sleep is disrupted, this can also lead to digestive issues. Sleep disruption from working shifts, particularly night shifts, is a common occurrence.
Jet lag can also disrupt the body's internal clock. Likewise, eating late at night or irregularly can also harm sleep. The circadian rhythm of sleep is controlled by natural sunlight.

Unfortunately, in today's technological age, we spend most of our daylight hours indoors. This reduces our connection to natural daylight and its benefits. Instead, we are exposed to blue light waves from laptops, televisions, mobile phones, and electric lights.
This shift can harm our health and well-being.  This can disrupt the sleep cycle and sleep patterns, especially if exposure to these light sources is immediately before bedtime.

The cumulative effect of one or more of these factors can harm gut health. It may lead to diarrhoea, ulcers, or inflammatory bowel disease. These issues can also disrupt the balance between beneficial and harmful bacteria in the gut.  It can also cause damage to the gastrointestinal lining.  

Microbiome Health 

The microbiome refers to the trillions of microbes residing in the gut. These primarily include beneficial bacteria known as probiotics. But it also includes viruses, fungal cells, and even some pathogenic bacteria. These microbes play a crucial role in overall health, as well as digestive health. They not only boost the immune system but also aid digestion, making some vitamins, enzymes, hormones, and amino acids.  Emerging research has shown that the microbiome also benefits human health through its connection with sleep. This is due to disrupted sleep or chronic insomnia, which can disturb the balance of microbes, potentially impacting digestive health and overall well-being. 

Interplay between the microbiome and sleep

The link between sleep and the microbiome is multifaceted and incredibly complex.
Poor sleep impacts the microbiome, and microbiome health, in turn, affects sleep. To explore this complicated relationship, one study examined bacterial cell counts and diversity in the gut. The study found that high numbers and a good mix of bacteria improved sleep patterns and quality.

These factors influenced how quickly people fell asleep and how often they woke during the night. They also affected the overall restfulness of the sleep. While all findings can't be covered here, the key takeaway is clear. Having a rich diversity of beneficial gut bacteria supports better sleep, digestion, and overall well-being.

Stress, sleep and digestion 

A common casualty of stress and anxiety is poor sleep. Likewise, these mental health conditions can also affect the physical health and function of the digestive system. This can affect gut motility, causing indigestion, ulcers, and irritable bowel syndrome. One reason stress affects digestion is due to the action of the hormone cortisol, often referred to as the “stress hormone.”  

Cortisol

When cortisol is present, it triggers the body to enter a state of fight-or-flight mode. Amongst other reactions, the body redirects blood flow to the heart, brain, lungs, and limb muscles. At the same time, it reduces blood flow to the digestive system. This enables the individual to either fight or run away from whatever is causing the danger and acute stress. In prehistoric times, this would have been a predator.  However, these days, stress is often caused by less life-threatening issues, such as paying bills, excessive workloads, or insufficient sleep.

Redirecting blood flow is helpful when escaping a threat, such as an attacking animal. Once the danger passes, blood flow returns to normal. However, chronic stress can harm the digestive system today. Gut motility may slow or become erratic, causing constipation, diarrhoea, gas, indigestion, and bloating. Having strategies to manage stress is essential for gut health. It also supports better sleep and overall well-being.

Getting plenty of sleep is vital for a healthy digestive system, as sleep and digestion are intrinsically linked. Therefore, prioritising good sleep hygiene is well worth doing. This involves minimising exposure to blue light from electronic gadgets. Go to bed and get up at the same time each day. Sleep in a cool, dark room for better rest. Avoid eating within two hours of bedtime to help maintain optimal sleep quality. Get outside in natural daylight during the day. Morning light exposure is invaluable for setting your body clock.

Connect with us on Facebook!

Medical Disclaimer:
The content on Jane Stevens Nutrition is for educational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider before making changes to your diet, lifestyle, or supplement routine. Use of this information is at your own risk. Jane Stevens Nutrition is not liable for any outcomes resulting from your use of this site. Full medical disclaimer here