Michael Breus, PhD (known as The Sleep Doctor) and gastroenterologist Doug Drossman, MD (the author of Gut Feelings, $40), have both extensively studied the gut-brain connection, including how sleep fits into the puzzle. Both experts explain that the gut-sleep relationship is complicated; this isn't a straightforward, easy peasy union. There's still a lot to learn about both gut health and sleep, but what we do know is that they are definitely intertwined.
Here, both experts explain how gut health and sleep are connected and give their best advice on how to improve your sleep through your gut.
1. Thriving healthy gut bacteria is linked to better sleep
Dr. Breus says that scientific studies have shown a strong connection between good gut bacteria (known as probiotics) and good sleep; there's even one particular bacteria strain that could make all the difference. "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," he says. "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." (It's a strain found naturally in the human microbiome, as well as in fermented foods like yogurt, he says.)
By the end of the study, the students in the probiotic drink group were enjoying more, higher-quality sleep than those in the placebo group—suggesting, the study authors wrote, that daily consumption of this particular probiotic might support sleep during times of stress.
It's important to note that the participants in this small study (fewer than 200 participants) were all students in Japan; including more people with different cultural backgrounds and eating habits would make the results more conclusive. "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," adds Dr. Breus. But the connection between probiotics and good sleep is still an interesting takeaway.
2. Bad gut bacteria is linked to poor sleep
Dr. Drossman has found with his work that the inverse is also true: just how good gut bacteria is linked to good sleep, bad gut bacteria is associated with poor sleep. "[Researchers] are still studying this and it isn't quite clear if the bad bacteria is affecting the brain or if the brain is affecting gut composition," he says. In other words: it's a bit of a chicken or the egg situation. To his point, one study published in the journal Public Library of Science found some evidence that while total microbiome diversity (aka the number of different microbes in your gut) is associated with better sleep, the presence of certain specific bacterial strains correlated to poor sleep (although the evidence isn't super conclusive that sleep deprivation can change the gut microbiome).
3. Microbes produce sleep-regulating hormones
If you've spent even five minutes looking into how sleep works, you're probably at least a little familiar with melatonin, a hormone made by the pineal gland in the brain that regulates the sleep-wake cycle. Here's what Dr. Breus says many people don't know: microbes in the gut produce melatonin and other sleep-regulating hormones, such as serotonin, dopamine, and Gamma aminobutyric acid (GABA). "There are two types of melatonin, [one] from the pineal gland and intestinal melatonin," he explains.
Dr. Breus says that because microbes in the gut produce sleep-regulating hormones, gut health has a direct effect on circadian rhythm. Research surrounding how what we eat affects serotonin, dopamine, and GABA levels is an emerging field of study for using food to boost mood and lower depression. Because these same hormones are linked to the sleep cycle, this means eating with them in mind could potentially help you sleep better, too.
4. Poor sleep could be a symptom of irritable bowel syndrome
Dr. Drossman says that he has seen through patients and research that IBS can impact sleep. "We know that people with certain health conditions like gastroesophageal reflux disease [GERD] or IBS tend to have more disrupted sleep," he says. "[These conditions are] gut-brain interaction disorders, so factors affecting the gut will affect the brain—and vice versa." He explains that getting to the root causes of GERD, IBS, or other gut health disorders will not only lessen digestive distress, but will also help you sleep, too.
How to improve sleep through gut health
As both experts have shown, what's happening in your gut is very likely related to how well you sleep at night. But the big underlying question comes down to how to use this helpful intel to get better rest. Since there's a strong connection between good bacteria and good sleep (and bad gut bacteria and poor sleep), Dr. Breus recommends eating foods known to boost the good guys. "Your diet has a significant influence over the health of your microbiome," he says. "Diets heavy on sugars, fatty- and highly-processed foods 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."
Dr. Breus also recommends eating a wide variety of plants, which can help feed and support the growth of a wider range of beneficial gut bacteria. "A diet rich in whole fruits and vegetables is the foundation of healthy living, and healthy sleep," he says. "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." It's the same advice gastroenterologist Will Bulsiewicz, MD, previously told Well+Good, saying "it’s scientifically proven that the single greatest predictor of a healthy gut is a diversity of plants [in one’s diet]."
Watch the video below for more tips on how to eat with gut health in mind:
Treating existing gut health issues you may have can also help improve sleep. Dr. Drossman emphasizes that this may take the help of a gastroenterologist since gut conditions are so complex and individual, but something that can help across the board is doing what you can to manage the stress in your life. "Stress can alter the bacteria in the gut," he says. And as you know by now, when bad things are happening in the gut, it's bound to disrupt your sleep cycle. Even simple actions such as five minutes of deep breathing or meditation have shown to reduce stress and positively impact the gut.
While researchers are continuing to learn more about how gut health and sleep are connected, what's crystal clear is that there is a strong relationship. And like with any relationship, what's good for one party is good for the other. So just know that whenever you do something with gut health in mind—like making a mindful effort to eat a veggie-filled meal—you're already prepping yourself for a good night's sleep.
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