Having Trouble Sleeping? Your Diet May Be the Reason, According to a New Study

Sleep may be one of the most underrated health habits. When we don’t get enough of it, it can affect everything from mood and anxiety levels to immunity and heart health. But quality sleep can feel elusive to many of us. Whether you have a sleep disorder, like sleep apnea or insomnia, or find it difficult to unplug earlier in the evening so you get enough sleep, you’re not alone. Around 40% of American adults are not getting sufficient sleep, according to the Centers for Disease Control and Prevention.

Sometimes the reason for insufficient sleep is difficult to figure out. If you feel like you’re doing everything right—you’ve got a bedtime routine that prepares your body for sleep and you sleep in darkness, allowing your body to produce melatonin—and yet, you still don’t sleep well, you might have a microbiome problem. A new literature review published on July 13, 2024, in Nutrients sheds some light on this very topic. Let’s see what these researchers found when they dug into 203 studies on the sleep-gut connection.

What Does This Study Show?

Your gut contains millions of different microorganisms—both beneficial and potentially damaging—that influence gut and overall health. These microorganisms produce metabolites—substances that are necessary for or a result of chemical reactions in the cells. All these microorganisms and their metabolites make up your microbiome—and this includes disease-causing bacteria, as well as health-inducing types of bacteria.

According to these researchers, our microbiomes begin to form at birth when the baby picks up bacteria—including healthy, beneficial bacteria—from the mother’s skin and vagina, depending on whether it’s a vaginal or cesarean birth. By the age of 5, the foundation of gut bacteria has been laid. And while it’s established early on in life, the microbiome will fluctuate throughout our lives, depending on many factors including diet, sleep, stress, exercise, medications, infections and environment. 

Besides building a healthy gut, these microorganisms also produce chemicals (metabolites) necessary for overall good health. One of these is serotonin, which acts as both a hormone and a neurotransmitter (neurotransmitters carry messages between nerve cells) and plays a pivotal role in your body’s circadian rhythms, cognitive function, pain perception and emotional control. Circadian rhythms are a type of biological clock and are related to sleep-wake cycles. When you’re regularly operating outside of your body’s natural circadian rhythms, you’re more likely to get less quality sleep. It also affects your microbiome’s health.

Serotonin is a precursor of melatonin, the chemical that is necessary for sleep. In other words, you must have enough serotonin to produce melatonin. And you must have enough melatonin to get good sleep. And to have enough serotonin, you need a healthy gut. 

Are you starting to see a connection here?

Gamma-aminobutyric acid, GABA for short, is another chemical that is produced in the gut. GABA plays a role in stress relief and sleep regulation. Like serotonin, you must have a healthy gut to produce enough GABA.

Then there are short-chain fatty acids (SCFAs). These are formed in the gut from fiber, polyphenols (antioxidants) and omega-3 fatty acids. According to these researchers, certain types of SCFAs can signal the brain when it’s time to sleep. There is evidence that people with insomnia have been shown to have a decrease in the number of these SCFAs in their gut.

SCFAs also influence the production of serotonin and GABA. You must have enough SCFAs in your gut to produce enough serotonin (which, remember, is a precursor of melatonin) and GABA, which in turn will influence your sleep.

It’s important to note that all of these connections are bidirectional. For example, while these metabolites—SCFAs, serotonin, melatonin and GABA—can affect sleep, sleep also influences the production of these metabolites. And so the cycle goes.

This literature review also revealed what foods contribute to a healthy gut and which ones negatively affect the microbiome. Regular, excessive intake of saturated fats, sugar, red and processed meats, and alcohol changes the microbiome in unhealthy ways. 

Foods that are high in fiber, polyphenols and unsaturated fatty acids, on the other hand, can stimulate the growth of beneficial bacteria and inhibit the growth of unhealthy bacteria, supporting a lush microbiome that’s loaded with beneficial bacteria and metabolites.

These researchers also point out that the timing of eating matters, too. They found that studies suggest that eating later at night can negatively affect circadian rhythms and the microbiome. There is also evidence to suggest that eating at regular intervals helps with circadian rhythms, whereas irregular eating patterns and skipping meals can mess with the rhythms—and consequently, the microbiome.

How Does This Apply to Real Life?

At EatingWell we believe that all foods can fit into a healthy, balanced diet and that health is about overall patterns. This means that occasionally eating something sweet or having an old-fashioned bologna-and-cheese sandwich on white bread is probably OK in moderation—“probably” because it depends on each individual’s health status and lifestyle. But it's important to consider your eating pattern as a whole. 

Are you regularly noshing on a variety of foods that are high in fiber, antioxidants and healthy fats? This includes fruits, vegetables, nuts, seeds, whole grains and seafood. Many plant-based foods act as prebiotics, providing food for your beneficial bacteria so they can multiply and thrive.

While this study doesn’t specifically mention fermented foods, we know that they also contribute to a healthy gut by adding probiotics—the beneficial bacteria in our microbiome. This includes foods like yogurt, kefir, sauerkraut and miso. 

This also applies to other health habits. For example, we all go through stressful times in our lives. It’s when that stress becomes chronic and habitual that it negatively influences our health. Same with sleep. 

To start, examine your current patterns in the areas of eating, exercise, stress and sleep. Are your patterns contributing to health or deterring from it?

The Bottom Line

This literature review includes hundreds of studies that help connect the dots between sleep and gut health. Hormones that contribute to quality sleep are produced in the gut, so it makes sense that you need to have a healthy, thriving microbiome to produce these hormones at optimal levels. Including a variety of foods that support gut health and limiting those that don’t will go a long way toward cultivating a healthy microbiome. It’s important to remember that this is a bidirectional relationship. While your microbiome will influence your sleep, how much quality sleep you’re getting will influence your microbiome. Other health habits also influence gut health, including diet, exercise and stress.