When it comes to dealing with stress, we’re often told that the best options are to exercise, make time for activities you enjoy, or meditate or make mindful efforts.
But according to research I’ve published with other members of APC Microbiome Ireland, the type of food we eat can also be an effective way to combat stress. Our latest study showed that eating more fermented foods and fiber on a daily basis for just four weeks had a significant impact on reducing perceived stress levels.
healthy menu healthy diet
The news doesn’t take us by surprise. Over the past decade, a growing body of research has shown that diet can have a huge impact on our mental health. In fact, a healthy diet may even reduce the risk of many common mental illnesses.
The mechanisms underlying the effects of diet on mental health are not yet fully understood. This may be linked to a connection between our brain and our microbiome (the trillions of bacteria that live in our gut) through the so-called gut-brain axis.
This two-way communication pathway allows the brain and gut to be in constant communication, and enables essential bodily functions such as digestion and appetite. This also implies that the emotional and cognitive centers of the brain are closely linked to our gut.
Onion, apple, banana and oats against stress
Although previous research has shown that stress and behavior are also linked to our microbiome, until now it was unclear whether changing our diet (and thus our microbiome) could have a different effect on stress levels.
To verify this, in our study we recruited 45 healthy people between the ages of 18 and 59 who had a relatively low fiber diet. More than half were women. The participants were divided into two groups and randomly assigned a diet during the four weeks of the study.
About half were given a diet designed by nutritionist Kirsten Berding that would increase the amount of prebiotic and fermented foods they ate. This diet is known as the “psychobiotic” because it includes foods that are associated with better mental health.
This group received one-on-one educational sessions with a dietician at the beginning and midway through the study. They were told to include 6 to 8 daily servings of fruits and vegetables high in prebiotic fiber (such as onions, leeks, cabbage, apples, bananas, and oats), 5 to 8 servings of grains per day, and 3 to 4 servings of Legumes a week.
They were also told to include 2-3 servings of fermented foods a day (such as sauerkraut, kefir and kombucha). Control diet participants only received general dietary advice based on the healthy eating pyramid.
Microbiota produces various substances
Interestingly, those on the psychobiotic diet reported feeling less stressed than those on the control diet. Furthermore, there was a direct correlation between participants’ strict adherence to the diet and their perceived stress levels: those who ate more psychobiotic foods felt less stressed.
Sleep quality improved in both groups, although the improvement was greater in those who followed the psychobiotic diet. Other studies have also shown that gut microbes are involved in the sleep process, which may explain this connection.
The psychobiotic diet produced only subtle changes in the composition and function of the gut microbes. However, we do see significant changes in the levels of some key chemicals produced by these gut microbes. Some of these chemicals have been linked to mental health, which may explain why dieters reported feeling less stressed.
Limitations: Small sample, short duration and only among healthy people
Despite the encouraging results, our study is not free from limitations. First, the sample size is small because the pandemic restricted recruitment. Second, the short duration of the study may have limited the changes we observed, and it is unclear how long these would last. Therefore, long-term studies will be needed.
Third, although participants recorded their daily diet, this form of measurement may be susceptible to error and bias, especially when estimating food intake. And while we did our best to ensure that participants did not know which group they were assigned to, it is possible that they could make guesses based on the nutritional advice they were given. This may affect the answers they give at the end of the study.
Finally, our work only involved healthy people, so we don’t know what effect this diet might have on someone who isn’t so healthy.
Nevertheless, our study provides strong evidence that changing your diet is an effective way to reduce stress in the long term. In addition to adding evidence to this area of research on the connection between diet, our microbiome, and our mental health. It will be interesting to see whether these results can also be reproduced in people suffering from stress-related disorders such as anxiety and depression.
So the next time you’re feeling particularly stressed, you might want to think more carefully about what you’re planning for lunch or dinner and incorporate more fiber and fermented foods.
With inputs from RTVE