Gut bacteria produce certain chemicals, called muramyl peptides, that are thought to be sleep-inducing. Some gut bacteria such as Corynebacterium and Brevibacterium produce the hormone serotonin which is tied to the body’s sleep/wake cycle.
Gut-dwelling bacteria, called the gut microbiota, have increasingly gained attention in recent decades. Their importance in our overall health and wellness is taking center stage these days because, as it turns out, they play crucial roles in many of our bodily processes.
One of the brain-related influences of gut bacteria is on our sleep cycles. Therefore, if you find yourself tossing and turning throughout the night, it could be because your intestinal tenants are keeping you up at night!
The how and the whys are yet to be fully understood, but scientists have found some definite answers related to the way gut bacteria works in our body.
Gut Bacteria Signal The Brain
In the 1960s, a study found certain bacterial compounds in the cerebral spinal fluid—a colorless supportive fluid that surrounds the spinal cord and brain—of sleep-deprived goats. Further research determined that these bacterial compounds may have come from gut bacteria. This was theorized because these bacterial compounds were proteins that matched those found in bacterial cell walls.
These proteins, named muramyl peptides, are thought to be sleep-inducing, so this research led to the strikingly new finding that sleep can be affected by gut bacteria, even though the exact mechanism as to how these peptides work remains unclear.
There have only been a few studies that have looked at the details between gut bacteria and the sleep cycle. One such study found that even slight sleep deprivation resulted in a change in the types of gut bacteria present within 2 days.
We now know that gut bacteria can control our sleep cycles, and we also know that antibiotics tend to disrupt natural gut bacteria colonies. One fascinating and very recent study put these two puzzle pieces together; they found that mice treated with antibiotics had dying gut bacteria that altered their sleep/wake cycle. This means that if there is some type of disturbance amongst our gut bacteria, we may not get our usual blissful nights of sleep.
Diet Can Affect Sleep
So what else can affect our gut bacteria that makes them keep us awake? Yes, you guessed it—food! If I had to pick one thing in life that plays a significant role in health and wellness, it is what we eat and when we eat it.
When gut bacteria are happily eating the food we so generously put in our bodies, they produce certain compounds or metabolites. These metabolites include serotonin and glutamate. These metabolites can travel through our blood or interact with our nervous system in order to reach the brain. This route of communication from the gut to the brain is the infamously named gut-brain axis.
Serotonin is a hormone that controls sleep and works in tandem with melatonin. Serotonin is a happiness hormone that keeps us energized and active. On the other side of the spectrum is melatonin, which makes us sleepy, tired and lazy.
Both are dependent on each other, meaning that we need serotonin to make melatonin. If there isn’t enough serotonin to make our sleepy hormone melatonin, then we won’t get the fruitful sleep we need.
Glutamate is a somnogenic neurotransmitter, which means it induces sleep. Studies have found that glutamate levels are highest during Rapid Eye Movement (REM) sleep, which is the state of sleep in which we dream.
Any disruption in our gut bacteria caused by poor diet can change the levels of these sleep-inducing metabolites and mess with our sleep/wake cycles.
Probiotics can help improve sleep
Logic dictates that gut bacteria affect sleep. In that case, making improvements and changes to our gut bacteria with the help of probiotics should also be able to improve sleep.
Working off this hypothesis, one very interesting study explored whether probiotics could help improve sleep. Stressed medical school students who were stressed out with exams and assignments weren’t sleeping too well. They were randomly split into two groups, with one given probiotic milk and the other given plain milk.
The probiotic milk was fermented with a strain of bacteria; Lactobacillus casei. You might have come across this bacterial strain in the form of a famous probiotic drink—Yakult.
The study found that the students who were given the probiotic milk reported sleeping better than those students who were given plain milk.
Though plenty of studies have been done on how probiotics improve sleep, most of these used animal subjects. Human studies remain limited and would need to be done on a much larger scale to understand just how much probiotics benefit sleep quality.
When we don’t sleep enough, our brains don’t perform at 100%. As a result, we have a growing population that struggles with sleep deficiency in the madness of these modern times. Focusing on ways to improve sleep is truly an essential task. One of the best ways to do this is to modify the gut bacteria using either medicine, probiotics or an altered diet.
With hundreds of different species and trillions of bacteria in the gut, figuring out how to maintain a healthy gut microbiota that results in better sleep is a huge challenge. Getting them to work in a way we want won’t be easy, but success will definitely be worth the pain!