The Gut-Sleep Connection

You’ve probably noticed that when you’re sleep-deprived, you’re more susceptible to the flu or a cold. That’s no coincidence. Like an overheated computer, it’s your immune system malfunctioning because it’s not getting the sleep it needs.

While you sleep, your immune system is hard at work producing infection-fighting antibodies and cytokines that help protect you from pathogens. A study published in the journal Sleep found that people who got at least seven hours of sleep were four times less likely to come down with a cold than those who clocked fewer than six hours, and fewer than five hours of nightly sleep (or fragmented sleep) correlated with an increased risk of coming down with pneumonia.

This dramatic state of immune deficiency associated with sleep deprivation happens quickly—after just one night of poor sleep. Fewer than four hours of sleep is correlated with a 70 percent drop in critical immune cells the next day. There is no denying that good sleep is absolutely essential if you’re trying to stay healthy and avoid coming down with a virus. But what’s the connection between good sleep and good guts?

Your gut impacts your sleep in two important ways: through regulation of a critical sleep hormone, and communication with your brain known as the gut-brain axis.

Serotonin is sometimes referred to as the “feel-good” hormone because of its stabilizing effect on mood, feelings of well-being, and happiness. Manufactured from the amino acid tryptophan, about 80% of serotonin is made by the bacteria in your gut. Serotonin is also the precursor for the sleep hormone melatonin, so an imbalanced or unhealthy community of gut microbes (dysbiosis) can affect serotonin production, which in turn affects melatonin production. And, as you’ll see, melatonin is critical for falling asleep.

How critical? Your circadian rhythm, your body’s internal process that regulates your sleep-wake cycle, relies on melatonin to do its job. As it gets darker, your eyes sense less light and send a message to your brain via your optic nerve that night is coming. In response, your brain increases melatonin secretion to make you sleepy. That’s why darkness—and the melatonin it induces—is so essential for falling asleep. In the morning, the opposite happens: as light increases, melatonin secretion decreases, and you wake up.

In addition to the hormone connection, an unhealthy gut microbiome produces inflammatory metabolites that can travel from your gut to your brain and disrupt the chemical signaling required for healthy sleep. And of course the converse is true: a healthy microbiome leads to healthy gut-brain communication pathways that enhance rather than disrupt your sleep, ensuring that your immune system is rebooted and ready to do battle.

Just as disordered sleep affects your health and well-being, restoring sleep is just as impactful in making your life better, and that can happen with just a few days of good sleep hygiene. Here are seven gut-based tactics to help you get the shut-eye you need to keep you rested and healthy.

1) EAT SOME TRYPTOPHAN: Tryptophan is an essential amino acid that can’t be produced by the human body and must be obtained through your diet, primarily from animal- or plant-based protein sources. Make sure you’re getting enough by consuming foods high in tryptophan, which include peanuts, pumpkin and sesame seeds, chicken, eggs, fish, turkey, tofu, and unprocessed non–genetically modified soy.

2) TRY SOME FERMENTS: Fermented foods like sauerkraut, kimchi, and even pickled vegetables can improve the health of your microbiome, which helps boost serotonin levels and melatonin production.

3) AVOID CAFFEINE: Caffeine has a half-life of several hours, so don’t drink any caffeinated beverages past noon—or cut them out altogether. Even though you may think afternoon or evening caffeine doesn’t bother you, studies show it affects everyone’s quality of sleep.

4) LIMIT ALCOHOL: Alcohol doesn’t make you sleepy, it sedates you, and sedation and sleep are not the same thing. Alcohol is a major sleep disruptor, so if you’re trying to establish a good sleep routine, reducing or avoiding alcohol is really important. If you are going to drink, limit it to not more than one alcoholic beverage and not within two hours of bedtime.

5) DRINK A LITTLE CHERRY JUICE: Fruit juice, even the unsweetened kind, is not a beverage I usually recommend because of the high sugar and low fiber content, but if you’re trying to cut down on alcohol, sipping on some tart cherry juice instead can be a helpful substitute. Tart cherries contain tryptophan and anthocyanins, two compounds that help the body create melatonin. Research shows that supplementing with tart cherry juice increases levels of melatonin and helps improve sleep quality and duration. In one study where participants suffering from insomnia drank either 16 ounces of tart cherry juice or the same amount of a placebo juice each day for two weeks, sleep time increased by an average of eighty-five minutes in the cherry juice group. Those results are superior to valerian and melatonin—the two most studied natural products for insomnia.

6) SIP SOME TEA: Chamomile and passionflower tea have been found to help with sleep, and the nightly ritual of sipping on a cup of tea can also be soothing. Establishing a routine of herbal tea before bedtime can become part of your signaling mechanism that it’s time to wind down.

7) EAT EARLY: Digestion is an active process that can stimulate you and keep you awake. Eating too close to bedtime can also lead to heartburn, which is very disruptive to sleep. Try to finish dinner at least three hours before bedtime and avoid heavy meals at night.