Immune System Influences Relationship Between Sleep and Gut Health
It has long been recognized that a lack of nighttime sleep opens us up to a greater number of medical conditions. People who work nights or graveyard shifts are significantly more likely to develop cancer, ulcers, obesity and a long list of other illnesses, which suggests that the circadian rhythm plays a role.
In the most recent study, researchers working out of Portugal’s Champalimaud Centre for the Unknown wanted to see if the lymphoid immune cells (ILC3 cells) that help the body fight off infection were influenced by the body’s circadian rhythm. Using mice, the team found that ILC3 cells were very sensitive to changes in the circadian rhythm. In fact, they noted that there was a circuit in the brain that directly connects the circadian rhythm to the ILC3 cells in the gut.
When the body’s biological clock is disrupted by changes to the normal cycle of light and dark, the ILC3 cells are also affected, disrupting the entire gut microbiome as well as the body’s lipid absorption rate. In short, a dysregulated circadian rhythm resulted in changes to both metabolic health and intestinal inflammation. When the circadian rhythm is disrupted regularly, the researchers found that it resulted in fewer ILC3 cells in the gut microbiome. This led to higher instances of inflammation throughout the body and an increased risk of obesity.
Normally, there is a protein that tells the ILC3 cells where to go to help protect the body. However, disrupting the sleep patterns and altering the circadian rhythm prevents this protein from functioning properly. As a result, the ILC3 cells don’t know where to go and the immune system is weakened. This may explain why people with irregular sleep patterns also take longer to heal or recover from sickness.
How Does Sleep Affect Gut Health?
We’re just beginning to learn that there’s a relationship between sleep quality and the health of the gut microbiome. This is a reciprocal relationship, meaning a deficiency on one end will result in a deficiency in the other. In 2016, researchers tested this relationship in a study that used nine male subjects. The subjects were in good physical condition, had not experienced any sleep disorders and consumed regular diets.
When the participants were deprived of sleep for just two nights, the researchers noted some significant changes in their health: They found that the test subjects had experienced a drop in the number of healthy bacteria in their gut microbiomes. There was a notable increase in the bacteria that affected obesity and type 2 diabetes as well. Finally, they noted that the body of each participant exhibited decreased insulin sensitivity.
That relationship works in the opposite direction as well. Studying subjects aged 50 to 85, researchers in another study looked at how a compromised gut microbiome affected sleep and cognitive functioning. They discovered that a healthier and more diverse gut microbiome resulted in subjects getting better-quality sleep. Their cognitive functioning was also improved, although it’s difficult to say whether this was directly related to gut microbiome diversity or to getting a good night’s sleep. Better sleep and more bacterial diversity may have played equal parts in helping subjects improve their cognitive functioning. While more research is needed, it’s clear that a healthy gut microbiome does affect sleep quality just as sleeping habits influence the health of the gut microbiome.
Sleep and Immunity
In other research, it was found that the quality and duration of sleep can also affect the functioning of the immune system. This is because the immune system releases proteins called cytokines during sleep, which affect the body’s ability to fight off illnesses and infections. If you’re not sleeping well, your body won’t produce a sufficient amount of cytokines, which means you’ll have a greater risk of developing inflammation or infections.
While you’re sleeping, your body is working hard to repair the strain or damage that you experienced throughout your waking hours. This means sending out antibodies to help reduce inflammation and tissue damage. The body needs seven to eight hours of sleep each night to accomplish this task, so by failing to get enough sleep, you’re also hampering this process. This is why you feel more fatigued and less productive when you don’t get enough sleep.
Over time, you build up a sleep deficit, leaving your immune system in an extremely weakened state. As a result, you’ll feel more stressed and you’ll be more prone to develop illnesses or infections. The relationship between sleep and immune system functioning also explains why people working night shifts are more likely to contract colds or the flu. The link between sleep and immunity further explains why getting enough sleep every night is essential to overall health.