I’ve been having lots of conversations lately about sleep and gut health, with patients and with colleagues. (I recently talked with the UK’s The Guardian newspaper about the topic.) I wanted to bring some of these conversations back here, because there have been some significant new scientific developments in our understanding of the relationship between sleep and our microbiome. (You can check out some of my previous writing on the sleep-gut connection here.)
What’s the microbiome?
You’ve probably heard about the importance of “gut health” to your overall health and well-being. Your intestines are home to the largest concentration of micro-organisms that make up what scientists call the “microbiome.” This microbial world within us plays an important role in digestion—and a whole lot more.
The human microbiome is made up of trillions of tiny microbes. Many are bacteria, but there are also viruses, fungi, and protozoa. These microbial organisms live all throughout the body, but it’s the large microbial ecosystem in the intestines that has attracted the most attention, because of all we’re learning about its role in maintaining physical and mental health and function.
Here are some fast facts about the microbiome:
- It’s often referred to as our “second brain.” Why? Our microbiome is home to a nervous system and about 100 million neurons. The nervous system of the microbiome is in constant communication with the brain and our central nervous system, helping to regulate hormone production, immune system function, appetite, digestion and metabolism, mood and stress responses.
- The intestinal microbiome produces and releases many of the same sleep-influencing neurotransmitters—dopamine, serotonin, and GABA among them—that are also produced by the brain. Melatonin is produced in the gut as well as the brain.
- Every individual microbiome is different, and develops as a result of genetics as well as exposure to microbial life, in our environment and in our diet.
- The microbiome is a highly dynamic internal ecosystem, with a constantly shifting make-up of micro-organisms. Most are beneficial to the body’s health, and some smaller number of others are potentially disease-promoting. There is a natural balance that occurs in a healthy body’s microbiome. When that balance is upset, the body may be at greater risk for disease.
- The make-up and the diversity of organisms within the microbiome—both the types and amounts of different bacteria and other microbes—appears to have a truly widespread effect on mental and physical health, influencing mood, metabolism, cardiovascular and circulatory health, as well as the immune system, and our risk for chronic disease.
- Like sleep, and so much else about the body, it appears our microbiome is regulated by circadian rhythms. Emerging research indicates that when circadian rhythms are disrupted, the health and functioning of the microbiome suffers. The health of the microbiome can also be disrupted by poor diet, stress, illness, and overuse of medications including antibiotics.
Let’s take a look at some of the newest and most interesting discoveries that have been made about the relationship between sleep and gut health.
It doesn’t take long for poor sleep to affect your gut
The relationship between sleep and the microbiome is increasingly seen as a two-way street. Our microbiota seems to have an effect on how we sleep. In turn, sleep and circadian rhythms appear to affect the health and diversity of the important bacterial world that lives in our gut.
We’re still at the very beginning stages of understanding this complicated, dynamic relationship. Recent research shows not sleeping enough can quickly have a negative effect on microbiome health.
A 2016 by a group of Swedish and German scientists were among the very first to investigate the impact of insufficient sleep on the composition of the human microbiome. It’s a small study that included nine healthy, young, normal weight men. None of the participants suffered from any sleep disorders, and all had regular sleep patterns and regular eating patterns. After only two nights of partial sleep deprivation, scientists found:
- A significant decrease in types of beneficial bacteria
- Changes to the composition of micro-organisms in the microbiome that are linked specifically to obesity and type 2 diabetes
- A significant decrease in insulin sensitivity
In a two-part series on diabetes, I wrote about the relationship between sleep and metabolic health—including the impact of poor sleep on insulin and blood sugar.
Unhealthy gut may be a link between poor sleep and cognitive decline
There’s a lot of attention paid these days to the potential effects of the microbiome on mental and cognitive health. That’s with good reason. There’s increasingly strong evidence that gut health may be an important factor in the onset of depression, anxiety, and other mental health disorders, including post-traumatic stress disorder. Medications for depression may also affect the microbial life within the gut, and the ability of those drugs to effectively treat the condition.
It probably shouldn’t surprise us much that our “second brain” may have a significant impact on our cognitive health. A 2017 study by researchers at Kent State points to a possible role of the microbiome in the relationship between poor sleep and age-related cognitive decline.
Researchers investigated the influence of the microbiome in a group of adults ages 50-85. They found strong connections between higher sleep quality, better cognitive flexibility, and higher levels of beneficial gut microbes.
Could the effects of poor sleep on gut bacteria be one way that poor sleep contributes to cognitive decline in older adults? Could a healthy gut help protect against the impact of poor sleep on cognitive health? Researchers in this study say it’s possible, and their preliminary findings need additional investigation.
Better understanding age-related cognitive decline is an important public health issue. I talked recently about the links between sleep and Alzheimer’s disease. There’s a growing body of evidence for sleep’s role in cognitive decline and neurodegenerative diseases like Alzheimer’s. Learning more about the microbiome, and its relationship to sleep, may give us critical new insight about how to protect the brain as we age.
Does gut health cause high blood pressure in people with sleep apnea?
I wrote a few years ago about scientific evidence showing that sleep-disrupted breathing can negatively affect the microbiome. Specifically, the interrupted breathing of obstructive sleep apnea appears to have a detrimental effect on the diversity of microbes in the gut. And the damage to the microbiome from sleep apnea may not be easy to correct, according to recent research.
Now, an emerging body of scientific evidence suggests the microbiome itself plays a role in causing high blood pressure in people with obstructive sleep apnea.
High blood pressure and sleep apnea frequently occur together. OSA significantly raises risk for high blood pressure, and high blood pressure can lead to the onset of sleep apnea. OSA-related high blood pressure can be difficult to treat, leaving people vulnerable to significant heart-health risks.
Fragmented sleep affects the microbiome and metabolic health
Fragmented sleep is restless, unrefreshing sleep that’s characterized by many frequent awakenings throughout the night. People who experience sleep disorders, particularly obstructive sleep apnea, often contend with this type of poor sleep quality, which keeps them from spending sufficient time in the most restorative stages of deep sleep and REM sleep.
We have an abundance of evidence that fragmented sleep leads to changes in metabolism and eating patterns that increase risks for obesity and other metabolic disorders, including type 2 diabetes. In the past several years, we’ve also seen a growing body of evidence that dysfunction in the microbiome is a significant factor driving the metabolic changes that lead to obesity and other metabolic disorders.
Recent research suggests that fragmented sleep may play an important role in the microbiome-driven effects on metabolic health, in part by triggering inflammation that leads to metabolic dysfunction.
The relationships between sleep, our microbiome and metabolism are complicated, and we’re just beginning to understand how they relate to one another. Taking steps to sleep better, and addressing issues of poor quality sleep and sleep apnea, can help you protect your metabolic health and reduce your risks for weight gain and diabetes.
Beneficial bacteria may protect against the upset stress causes to sleep
We know that stress is a major contributor to sleep problems. I see this constantly in my patients, as stress about work, finances, and family—which often come together in a pervasive feeling of being overloaded—wreak havoc with their sleep. We’re also learning more about the powerful connection between gut health and stress—one that runs in both directions. Research indicates that stress can negatively affect gut health, and poor gut health can exacerbate the body’s stress response.
Recent research shows that one strain of beneficial bacteria may help blunt the effects of stress on sleep. Scientists in Japan studied the impact of a daily serving of a probiotic on a group of students who were preparing to take an exam. Scientists divided the students into two groups. For eight weeks leading up to the exam, and three weeks after, one group drank a placebo beverage every day, while the other group drank a probiotic beverage containing the bacteria Lactobacillus casei strain Shirota (sometimes referred to as L. casei strain Shirota). The Lactobacillus type is one of the beneficial bacteria found naturally in the human microbiome. It’s also found in fermented foods like yogurt, and sold in supplement form.
Not surprisingly, both the placebo and probiotic groups experienced increasing stress as exam day approached. The placebo group also saw changes to their sleep. They started taking longer to fall asleep and spent less time in deep, slow-wave sleep, as their anxiety grew and test day grew closer.
The group taking the probiotic had a different experience. Their stress levels rose as the exam drew near, just as the placebo group’s did. But the probiotic group didn’t suffer the same negative changes to sleep. On the contrary, the probiotic group:
- Experienced less difficulty falling asleep under pre-exam stress
- Maintained, and even strengthened, their deep, slow-wave sleep
- Woke feeling more rested and refreshed than the placebo group
These findings suggest that the beneficial bacteria contained in the probiotic may have helped protect the students’ sleep during an otherwise stressful time leading up to an exam.
So, if stress impedes your sleep, does this mean you should start taking this particular probiotic? Not so fast. This is one small study—with fewer than 100 people in both groups. It will be important to see these results repeated in other scientific studies. Also, the microbiome is incredibly complex, and varies from one individual to the next. The bacteria that’s beneficial for one person, or small group of people, may not have the same effects on another person.
Still, these are some highly interesting results that point to the potential for our microbiome to influence how well we rest at night, and to the possibility of using probiotics and other microbiome-targeting therapies to protect and improve sleep.
Ways you can improve your gut health—and boost your sleep at the same time
We’ve got a lot still to learn about the human microbiome. But it’s clear that the microbial ecosystem in our gut has a profound influence over our health. Paying attention to your gut health may help reduce your risk for chronic diseases, including diabetes and heart disease. It may help protect your brain and your cognitive functions, and improve your emotional and psychological well-being. It also may help you sleep better.
Focus on whole, minimally processed foods. Your diet has a significant influence over the health of your microbiome. Diets heavy on sugars, fatty- and highly-processed foods in your diet can alter the make-up of your gut microbiome, reducing the abundance of beneficial microorganisms. Limiting these foods, and replacing them with whole, unprocessed nutrient rich foods like vegetables, fruits, and whole grains, can help restore and protect the beneficial bacteria in your gut.
Eat organic whenever you can. There’s research indicating that pesticides alter the microbiome, and are harmful to the beneficial bacteria we want to have thriving in our microbiome. Pay attention to lists like the Dirty Dozen and the Clean 15, and go organic when you can. Remember, organic isn’t only about fruits and vegetables. Look for organic sources of beans, grains, dairy, and other animal products, too.
Eat a wide variety of plants. A diet rich in whole fruits and vegetables is the foundation of healthy living, and healthy sleep. To give your body a true diversity of beneficial bacteria, pay attention to getting as broad a variety of plant-based foods as you can. This is often called “eating the rainbow,” of colorful fruits and vegetables—and it’s great for your gut health, as well as your nightly rest.
Take prebiotics. Prebiotics are an energy source (think: food) for the trillions of tiny organisms in your gut. High-fiber plant foods are good sources of prebiotics, including asparagus, apples, artichokes, bananas, as well as onions, leeks and garlic. Prebiotics are also available in supplement form. Recent research indicates a prebiotic-rich diet can reduce stress and improve sleep.
Eat smart at night. It’s not good for sleep to go to bed hungry. But eating too heavily close to bedtime revs up the digestive system, just when your body is naturally wired to give digestion a rest. At the end of a long day, when you’re mentally and physically tired, it can be harder to resist the cravings for sugar and processed fats, which can interfere with sleep and the health of your microbiome. If nighttime snacking is a temptation for you, plan to have a selection of sleep and microbiome-friendly options on hand.
The perfect pre-sleep snack is easy to digest, a combination of complex carbohydrate and protein, and around 200 calories. I recommend to my patients banana or toast with nut butters, whole-grain, no-sugar added cereal with milk. I also love Nightfood bars, which are designed to be a balanced pre-bed snack.
Get your exercise. You’ve heard me say it before: regular exercise is terrific for sleep. Exercise helps you fall asleep more easily, and sleep more soundly throughout the night. New research shows exercise also may directly benefit your microbiome. Researchers at the University of Illinois at Urbana-Champagne studied the effects of exercise on the microbiome in both mice and in humans, and found physical activity changed the composition of the microbiome, increasing the amounts of beneficial microorganisms that lead to lower inflammation. Scientists found the benefits of exercise on microbiome composition happened independent of diet.
In fact, you may have seen the press release, but I am now part of the Scientific Advisory Board for UBiome! This is an incredible company that helps us all learn more about our own microbiome and how to keep it strong.
We’ve learned a staggering amount about the microbiome and its relationship to sleep in recent years. Still, we’ve only just scratched the surface of what we need to know to truly understand this relationship. What’s increasingly clear? An investment in good sleep is an investment in a healthy gut. And taking care of your gut—by eating well, managing stress, and being active—can pay big dividends for sleep.
Michael J. Breus, PhD
The Sleep Doctor™