This Food Group May Be the Secret to Better Sleep, According to a New Study

Having trouble getting enough rest? A new scientific review suggests there might be a link between eating fermented foods and getting better sleep. 

A number of human and animal studies have discovered that probiotics — found in foods like kimchi, miso, and yogurt — helped subjects achieve better sleep, either by falling asleep more quickly, staying asleep for longer, experiencing deeper sleep, having fewer nighttime awakenings, or increasing morning alertness. The review is just the latest in a growing body of research into how the gut interacts with the brain, and what that could mean for improving your shut-eye.  

Published last month in the Journal of Food Science, the study was conducted by two researchers at the Central Food Technological Research Institute in Mysuru, India: research associate Akanksha Singh and Dr. Pradeep Sing Negi, chief scientist and head of the school’s Department of Fruit and Vegetable Technology. The two academics pored over years of research to learn everything they could about the relationship between fermented foods and how we sleep — here’s what you need to know.

What did this research analyze?

To reach their conclusions, Negi and Singh reviewed 61 scientific studies published between 1995 and 2024 relating to sleep, the brain, the gut, and the compounds that contribute to a healthy gut, known as “biotics.” Fermented foods such as kefir, sauerkraut, and tempeh — to name just a few — are made with controlled bacteria growth, which gives them one type of biotic (probiotics), along with their tangy flavor.

Several pieces of research that Negi and Singh looked at found connections between fermented foods and improved sleep. For example, one 2020 study found that fermented milk reduced insomnia in mice. Mice that ingested fermented carrot juice slept for longer, according to research from 2022, and rats that drank fermented milk and pomegranate juice had fewer sleep awakenings and more deep, restorative sleep in a 2023 study.  

Even more significantly, multiple instances of research on humans show similar results. A 2024 report on the findings of the National Health and Nutrition Examination Survey (NHANES) from 2009–2018, reviewing the responses of 49,693 American adults from this time frame, found that people who ate yogurt or took probiotic supplements reported fewer sleep disturbances. According to a smaller 29-person study from 2009, elderly adults who drank around a third of a cup of fermented milk each day fell asleep more swiftly and experienced a decrease in nighttime awakenings. 

Additionally, in one 2017 study of medical students, subjects drank a little less than a half cup of fermented milk each day over an 11-week period before and after exams. Students who drank the fermented milk maintained stable sleep quality, while subjects who took a placebo saw their sleep quality decline as the exams drew closer.   

How are the gut and the brain connected?

Fermented foods’ ability to impact sleep hinges on the relationship between the gut and the brain. The probiotics in fermented foods contribute to a healthy gut by introducing more good bacteria to your digestive system. 

There are trillions of microorganisms, including bacteria, already in your gastrointestinal tract. These are known as “gut microbiota,” and they’re crucial to the healthy functioning of your digestive and immune systems, in addition to many other bodily functions.

Probiotics add more beneficial microbes to your gut, and in turn gut microbiota connect to the brain through something called the “microbiota-gut-brain axis.” This axis mediates the relationship between the gut and sleep. So the chain of relationships here is: probiotics add good bacteria to your gut, gut bacteria is critical for many bodily systems including digestion, and the gut is connected to the brain, which means it’s also connected to your sleep. The microbiota-gut-brain axis is complex, but more and more research is seeking to understand it.

“Over the past decade, researchers have made incredible strides in understanding how the gut microbiota communicates with the brain via neurotransmitters, immune signals, and metabolic pathways,” Negi tells Food & Wine. “Researchers have moved beyond just recognizing the connection to actively exploring how we can manipulate the gut microbiota for benefits like reducing anxiety, improving mood, and even enhancing sleep quality.”

Part of what makes the gut-brain relationship so complicated (and fascinating) is its bidirectional nature, meaning that the gut affects the brain and vice versa. “Poor sleep disrupts the gut microbiome, leading to an imbalance of beneficial and harmful bacteria, which has been linked to increased inflammation, stress hormone imbalances, and even metabolic disorders,” Negi explains. “On the other side, an imbalanced gut microbiome can impair sleep by influencing neurotransmitters, immune responses, and even melatonin production.”

Researchers are exploring the role of the gut-brain axis in other areas of medicine, too. “There is so much interest in the microbiota–gut–brain axis, especially when learning about Parkinson’s and other neurological disorders,” Dr. Rachel Salas, a professor of neurology and Assistant Medical Director at the Johns Hopkins Center for Sleep and Wellness, details to Food & Wine. 

Salas points out that neurological research and sleep research can overlap, explaining that  “Many patients with Parkinson’s have REM behavioral sleep disorder as well, and there is certainly research on how all this connects… The gut is so important not only for our nervous system, but also sleep.”

Should you be eating more fermented foods to improve your sleep?

According to the analysis by Negi and Sing, findings indicate that integrating biotics into your diet may help address sleep-related issues. This includes both probiotics (bacteria found in fermented foods like sauerkraut and kefir) and prebiotics (fiber found in foods like beans and oats). 

However, the two academics also emphasize the need for more research. The existing body of research into fermented foods and sleep is limited by small sample sizes and varying study designs. For example, different studies use different strains of probiotics. This makes it difficult to draw any overarching conclusions, even though existing research does indicate fermented foods could likely help improve sleep quality.

Because conclusions are not yet clear, Salas doesn’t specifically recommend fermented foods for improving sleep quality, noting that, “While many patients are interested in suggestions on which foods to eat, I encourage them to stay more general and not go to bed hungry but also not have spicy or heavy meals at bedtime. 

“After that, it is all about experimenting. I certainly have patients that do eat particular foods (like fermented foods) that they say seem to help their sleep. I might mention that fermented foods have some research behind [them] supporting sleep and overall gut health.”

If you want to experiment yourself and add more fermented foods into your diet, there are a wide variety of options to enjoy. You can try miso, kombucha, tempeh, dairy products like kefir, yogurt, buttermilk, and even cheeses like provolone, Gouda, and cheddar. You can also eat brined vegetables like kimchi, sauerkraut, and (sometimes) pickles.

When purchasing pickles, double check to make sure they’re actually fermented, not just pickled in vinegar. If you only see salt, spices, and vegetables on the ingredient list, then they’re almost certainly fermented. These fermented veggies pick up their sour flavor from the reaction between bacteria and the vegetable’s naturally occurring sugar, but if you see vinegar in the ingredient list, it may be a sign that the pickles get their acidic profile from the extra ingredient, and not the process of fermentation.

What’s next?

Before you can look to science to tell you exactly which fermented foods — and how much of them — to eat for a better night’s sleep, researchers will need to conduct more studies. This most recent review recommends that future analyses observe larger and more diverse human populations and adopt standardized research protocols.

The complex, bidirectional nature of the gut-brain relationship also poses a challenge, as it makes it difficult to isolate cause and effect. For Negi this raises the question, “Does poor sleep change the gut, or does an altered gut microbiome cause sleep disturbance?” To solve this issue, he suggests that researchers use controlled trials and advanced microbiome sequencing, which could help scientists better understand microbes’ roles in the body.

Still, the future of research into fermented foods and sleep looks bright. “New studies emerge regularly, particularly in the fields of probiotics, prebiotics, and personalized nutrition,” says Negi. “Future research will likely focus on precision probiotics, tailoring specific strains for targeted benefits like better sleep or reduced stress.” And in the meantime, it can’t hurt to incorporate some more sauerkraut, kombucha, yogurt, or your fermented food of choice into your daily diet.