Prebiotic and fermented foods can reduce stress and improve sleep

According to Dr. John F. Cryan, Professor and Head of the Department of Anatomy and Neuroscience and Principal Investigator at the APC Microbiome Institute at University College Cork, Ireland, and lead author of this study, the research team has been working on the relationship between stress and the gut microbiome for over 15 years since they discovered that animals stressed early in life had an altered microbiome.

“Mice that grow up without microbes have an exaggerated stress response, and certain strains of bacteria can attenuate stress in mouse models,” Dr. Cryan explained to Medical News Today.

“Whereas Previous search showed that stress and behavior are also linked to our microbiome, it was not clear until now whether changing our diet – and therefore our microbiome – could have a distinct effect on stress levels. This is what our study set out to do,” he said.

DTM also spoke with Lauren Pelehach Sepe, clinical nutritionist at the Kellman Wellness Center in New York, who delved into the link between stress and the gut microbiome.

“The microbiome is made up of an entire community of microorganisms that live in our bodies. This includes both beneficial bacteria and pathogenic microorganismswhich, if left unchecked, can harm our health.

“The digestive tract contains its own neural network called the Enteric nervous system, which allows direct communication with the brain or the “gut-brain axis”. The gut-brain axis is critical to our ability to handle stress – when the gut is out of balance, it impairs our ability to handle stress appropriately.
—Lauren Pelehach Sepe

Additionally, Sepe mentioned the vagus nerve – known as 10th cranial nerve – which directly connects the gut to the brain.

“In fact, damage to the vagus nerve has been shown to directly impact digestion by slowing stomach emptying. This is also why people often experience gastrointestinal symptoms when under stress” , she continued.

“Although more research is needed, consensus research has shown that there is a link between gastrointestinal dysfunction and stress-related conditions such as Anxiety depressionand irritable bowel syndrome,” she added.

For this study, participants ate foods rich in prebiotic and fermented foods. The researchers call it a “psychobiotic” diet, a term Dr. Cryan said his research team coined in 2013 to refer to microbiota-targeted interventions that support mental health. The psychobiotic diet was later the subject of his team’s book, The psychobiotic revolution.

For this study, Dr Cryan and his team recruited 45 people with a relatively low fiber diet, aged between 18 and 59, from the Cork region. The researchers asked participants in the psychobiotic diet group to eat daily:

• 6 to 8 servings per day of fruits and vegetables rich in prebiotic fiber, including onions, leeks, cabbage, apples, bananas and oats
• 5 to 8 servings per day of cereal
• 2 to 3 servings per day of fermented foods, including sauerkraut, kefir, or kombucha
• 3-4 servings per week of legumes

Meanwhile, the researchers told the participants in the control group to eat according to the food pyramid. And participants in both groups received advice from a registered dietitian.

At the end of the study, researchers found that those who ate a psychobiotic diet reduced their perceived stress – their feelings about the level of stress they were currently under. Additionally, scientists found that the more a person adhered to the psychobiotic diet, the more they reduced their feelings of stress.

“That was what we had expected, but we weren’t sure that the relatively short time window for testing would be enough to induce an effect,” Dr Cryan said.

After reviewing the study, Sepe said the psychobiotic diet includes foods that are naturally high in prebiotics — typically fiber-rich foods, which are the best food sources for beneficial gut microbes — and fermented foods, which are naturally rich in probiotics, the beneficial bacteria that inhabit our gut.

“These foods help promote a balanced and healthy gut microbiota, which, given the link between gut health and our stress response, can help us better manage stress,” she said.

The researchers also found that sleep quality improved in both the psychobiotic diet and the control groups.

Sepe says there are several ways diet can impact sleep. For starters, the gut and its microbes are responsible for producing serotonin – the precursor to melatonin, the hormone that regulates circadian rhythm and sleep.

“If we don’t produce enough serotonin due to an imbalanced gut microbiota, we will have reduced melatonin production, which will lead to sleep disturbances,” she explained.

Additionally, Sepe said, the gut microbiome plays a role in the production gamma-aminobutyric acid (GABA) — to neurotransmitter which promotes calming and aids sleep.

“Therefore, by eating a diet that supports a healthy gut microbiome, we ensure that we produce enough of these crucial neurotransmitters,” she detailed.

“[T]here, studies have shown that there is a link between gut microbiome composition, diversity, and sleep. Therefore, eating a diet that supports the gut microbiome and ensures its diversity also impacts healthy sleep patterns.
—Lauren Pelehach Sepe

For the next steps in this research, Dr. Cryan said he and his research team will try to figure out which component of the diet is more important – fiber or fermented foods.

“Furthermore, these were relatively healthy young participants – it will be important to see how the diet translates for those with stress-related disorders such as anxiety or depression,” he said. added.

Sepe mentioned that diet and nutrition studies are notoriously difficult to conduct because they rely on participants keeping food diaries and self-declaration, subject to errors.

“People generally struggle with dieting, so it’s hard to know for sure if people are really sticking to diet parameters,” she explained.

“While not an easy option, rather than letting people cook their own meals, it would be interesting to see a study like this done where perhaps some sort of meal delivery service was used, which can allow for more consistent eating and make it easier for people to stick to it,” she added.