When it comes to managing stress, we’re often told that the best things to do are to exercise, make time for our favorite activities, or try meditation or mindfulness.
But the types of foods we eat can also be an effective way to manage stress, according to research published by me and others at APC Microbiome France. Our latest study showed that eating more fermented foods and fiber daily for just four weeks had a significant effect on reducing perceived stress levels.
During the last decadea growing body of research has shown that diet can have a enormous impact on our mental health. In fact, a healthy diet can even reduce the risk of many common mental illnesses.
The mechanisms underlying the effect of diet on mental health are not yet fully understood. But one explanation for this link could be via the relationship between our brain and our microbiome (the trillions of bacteria that live in our gut). Known as the gut-brain axis, this allows the brain and gut to be in constant communication with each other, allowing essential body functions such as digestion and appetite to occur. It also means that the emotional and cognitive centers of our brain are closely linked to our gut.
Although previous research has shown that stress and behavior are also related to our microbiomeit was unclear until now whether changing our diet (and therefore our microbiome) could have a distinct effect on stress levels.
This is what our study aimed to do. To test this, we recruited 45 healthy people with relatively low-fiber diets, aged 18-59. More than half were women. Participants were split into two groups and randomly assigned a diet to follow during the four weeks of the study.
About half received a diet designed by nutritionist Dr. Kirsten Berding, which would increase the amount of prebiotic and fermented foods they ate. This is known as a psychobiotic dietbecause it included foods that have been linked to better mental health.
This group received an individual education session with a dietitian at the start and mid-point of the study. They were told they should aim to include 6-8 servings per day of prebiotic fiber-rich fruits and vegetables (such as onions, leeks, cabbage, apples, bananas and oats), 5-8 servings of cereals per day and 3 to 4 servings of legumes per week. They were also told to include 2-3 servings of fermented foods per day (such as sauerkraut, kefir, and kombucha). Participants in the control diet only received general dietary advice, based on healthy eating food pyramid.
Interestingly, those who followed the psychobiotic diet reported feeling less stressed than those who followed the control diet. There was also a direct correlation between how strictly participants followed the diet and their perceived stress levels, with those who ate more psychobiotic foods over the four-week period reporting the greatest reduction in perceived stress levels. .
Interestingly, sleep quality improved in both groups – although those on a psychobiotic diet reported greater sleep improvements. Other studies have also shown that gut microbes are involved in sleep processwhich may explain this link.
The psychobiotic diet caused only subtle changes in the composition and function of microbes in the gut. However, we observed significant changes in the level of some key chemicals produced by these gut microbes. Some of these chemicals have been mental health relatedwhich could potentially explain why plan participants reported feeling less stressed.
Our results suggest that specific diets can be used to reduce perceived stress levels. This type of diet can also help protect mental health long-term because it targets microbes in the gut.
Although these results are encouraging, our study is not without limitations. First, the sample size is small due to the pandemic limiting recruitment. Second, the short duration of the study might have limited the changes we observed – and it’s unclear how long they would last. Long-term studies will therefore be necessary.
Third, although participants recorded their daily diet, this form of measurement can be subject to error and bias, especially when estimating food intake. And while we did our best to make sure participants didn’t know which group they were assigned to, they might have been able to guess based on the nutritional advice given to them. This may have affected the answers they gave at the end of the study. Finally, our study only involved people who were already in good health. This means we don’t understand what effect this diet might have on someone who may not be as healthy.
Yet our study offers exciting evidence that an effective way to reduce stress may be through diet. It will be interesting to know if these results can also be replicated in people with stress-related disorders, such as anxiety and depression. This also adds further evidence to this search fieldshowing evidence of an association between diet, our microbiome and our mental health.
So the next time you’re feeling particularly stressed, you might want to think more carefully about what you plan to eat for lunch or dinner. Including more fiber and fermented foods for a few weeks may just help you feel a little less stressed.