The gut is arguably the most important part of the human body. It exerts an effect on practically every bodily function, which is why imbalances in the gut microbiome can have major impacts on both mental and physical health. The gut communicates with the brain via the brain-gut-microbiome-axis, or BGMA for short. This pathway is bidirectional, meaning that not only can the gut influence the brain and your behavior, but your psychological state can actually affect your gut health, too. Being under periods of high stress, for instance, has been shown to have negative effects on the gut microbiome. But it’s not just psychological stressors that exert this effect – physiological stressors can impact gut health, too. Sleep deprivation, for instance, is considered a physiological stressor, and can have major impacts on the health and functioning of the gut microbiome. How are sleep and the gut microbiome connected, and what are the consequences of the alterations that lack of sleep can lead to?
Sleep and the Gut
The gut microbiome is made up of millions, if not billions, of microorganisms that work symbiotically with the body. Everyone’s microbiome is different, but we all have a set ratio of “good” to “bad” bacteria within us. Certain stressors, such as sleep deprivation, can throw off this ratio, leading to what is known as “dysbiosis”. While sleep has been studied in depth for decades, research is just now beginning to emerge on the connection between sleep and the gut microbiome. Despite the fact that there are not a large number of studies available on this topic, practically all of the existing studies have noted the same finding – acute sleep-wake cycle disturbances (that is, short-term sleep losses) lead to alterations in the gut microbiome (2,3,4).
One study looked at the make-up of the gut microbiome at different time points. Fecal samples were collected the day before the experiment began (T0), the morning after a sleep time-shift (T1), and two days after participants returned to their normal sleep schedules (T2). There were no significant alterations between T0 and T2 (baseline and recovery), but at T1 (time shift), there was a significantly higher number of microbes present. This demonstrates that there is the tendency for a significant microbiome alteration immediately after a sleep loss, but that it can be quickly reversed after returning to one’s normal sleep routine (3). A similar study that compared sleep quality and gut microbiome composition in a sample of older adults found that there may be a relationship between sleep quality, gut microbiome composition and cognitive flexibility in this population (6).
In a 2020 study, researchers used the Pittsburgh Sleep Quality Index (PSQI) to evaluate subjects’ self-reported sleep habits, producing a score for each participant. A lower score indicated healthier sleep patterns, while a higher score indicated poorer sleep patterns. They then collected stool samples for each participant to create a profile of their individual gut microbiomes. When researchers compared PSQI scores to gut microbiome diversity, it was found that the ratio of Firmicutes to Bacteroidetes (F/B), as well as microbiome diversity, were inversely related to sleep quality scores (5). Meaning, the more diverse the microbiome and the higher the ratio of F/B, the lower the PSQI score. There is a large body of evidence demonstrating the importance of the F/B ratio in maintaining normal intestinal homeostasis, with an increase being associated with obesity and a decrease with conditions like inflammatory bowel disease, or IBD (7).
Sleep, the Gut, and the Immune System
A more well-studied area of research is the association between the gut and the immune system, as well as between the immune system and sleep. The three are connected, each indirectly influencing the other two and thereby impacting a person’s overall health. The immune system contains cytokines, which are signaling molecules that assist with cell-to-cell communication in the immune response and stimulate the movement of cells towards sites of trauma, infection and inflammation (8). The two important players in the connection with sleep appear to be the acute pathway cytokines IL-1β and IL-6. Cytokine IL-1β directly affects the sleep/wake cycle, and has been shown through studies to increase spontaneous sleep and fatigue when administered to both humans and non-human animals. Levels of this cytokine also increase with ongoing sleep loss (1). Cytokine IL-6 does not directly induce sleep, but sleep loss results in increased circulating levels of IL-6 (1). Levels of IL-6 naturally increase while you are asleep and decrease upon waking. High circulating levels during the day, therefore, indicate poor sleep quality (9).
Cytokines also demonstrate a potential connection between sleep physiology and the gut microbiome (1). When we look at the effects of IL-1β and IL-6 in the gut, we see that their expression leads to inflammation, and their levels fluctuate in response to disease and stress (1). Conditions like intestinal mucositis and chronic stress have been shown to lead to increased expression of these cytokines in the intestines (1). In a study that looked at the connections between sleep, cytokines and gut composition, it was found that IL-6 levels are positively correlated with microbiome diversity and measurements of sleep quality, such as time in bed and total sleep hours (1). Conversely, higher levels of this cytokine are negatively correlated with wake after sleep onset (or WASO), demonstrating its ability to help you stay asleep (1). It was also found that gut concentrations of Firmicutes and Bacteroidetes are associated with IL-6 and sleep efficiency, as well as abstract thought (1). A positive correlation was found between sleep efficiency and both diversity and richness of Bacteroidetes, and sleep efficiency and richness of Firmicutes (1). These results suggest that greater microbiome diversity, coupled with proper circulating levels of IL-6, promotes healthier sleep, as well as assisting in improving mental processes (1).
Complications of Poor Sleep Quality
There are a number of problems that can arise from lack of sleep. As mentioned earlier, sleep loss is considered a physiological stressor, and therefore impacts that BGMA. Alterations in the BGMA have been shown to be associated with a range of conditions, from gastrointestinal disorders to depression and anxiety (1). Poor sleep quality and short sleep durations have been directly associated with decreased cognitive performance, as well as diseases like type II diabetes, Alzheimer’s disease, and cancer (1). Poor sleep quality has also been shown to cause metabolic disturbances, causing certain gut bacteria to overgrow to mediate these alterations. However, the end-products of these bacteria can induce fatigue, thus further interfering with the circadian rhythm (4). This creates a feedback loop, pushing a person deeper and deeper into sleep debt and wreaking more and more havoc on a person’s health.
Improving Your Sleep
There are many lifestyle changes, like getting into a consistent bedtime routine and not using technology while you’re trying to sleep, that can help you to improve your sleep quality. However, for some people, sleep is still a struggle despite all of their efforts. In this case, supplements may be useful. Here are some that research has shown to be effective:
Melatonin is a naturally occurring hormone that helps to regulate the body’s sleep/wake cycle. It is known to help you to stay asleep after you’ve gone to bed, and can also help with the effects of jetlag (10).
Various essential oils have been shown to positively impact sleep. Lavender contains the compounds linalool and linalyl acetate, which can calm the nervous system, decrease insomnia and anxiety, and reduce sleepiness upon waking (11). It can also slow your heart rate, lower your skin temperature, and decrease your blood pressure (10). Cedarwood contains a compound called cedrol, which has been shown to improve sleep quality in young, healthy adults, as well as older adults with dementia (11). This compound activates the parasympathetic nervous system, helping to ease you into sleep, and may increase total sleep time while decreasing the number of early morning awakenings (11). Bergamot is a fragrant herb that is often mixed with various other essential oils to lower blood pressure and improve sleep quality (11). Add a few drops of any of, or a combination of, these oils to a diffuser or to your pillow and let them work their magic.
Chamomile contains the antioxidant apigenin, which provides a calming effect when ingested by acting on certain receptors in the brain to relax you and help you to fall asleep (10). Chamomile can be taken as an extract or drank as a tea to impart its beneficial effects.
Magnesium is a mineral that impacts many bodily functions. In regards to sleep, low levels have been shown to make it harder for you to fall asleep and/or stay asleep (10). Studies indicate that supplementation can improve sleep in older people as well as those with Restless Legs Syndrome (RLS), but more research is needed to determine its efficacy for the general population (12). You can check your magnesium levels through blood tests. InsightTracker offers blood tests for a wide variety of biomarkers, and provides personalized information to you based on your results. Use the code NUTRITIONREWIREDfor 20% off your plan plus a FREE InnerAge 2.0 ($179 value).
CBD is derived from the hemp plant and has been demonstrated to provide a wealth of benefits, such as reducing anxiety and improving sleep. The compounds in CBD that create these effects are known as terpenes, and there are hundreds of them. Two that are known to directly affect sleep are picene, which can induce REM sleep, decrease the time it takes to fall asleep, and lower anxiety, and myrcene, which has sedative effects (13). CBD comes in a variety of products, from oils to salves. I offer a CBD blend specifically for sleep, which contains other sleep-enhancing ingredients like lavender oil, valerian root, and added terpenes. If you’re interested in learning more about CBD, check out this article to help you find which product is right for you.
Disclaimer: Some herbs and supplements can interfere with certain medications – always talk to your doctor before starting something new.
For information on ways to improve your gut health, check out some of my previous blog posts (such as this one on high-fiber foods).
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