Fermented foods and fiber can reduce stress levels

When it comes to dealing with stress, we’re often told that the best option is to exercise, find time for our favorite activities, or try meditation or mindfulness.

But the type of food we eat can also be an effective way to deal with stress, according to research I published with other APC Microbiome Ireland members. Our latest research has shown that consuming more fermented foods and fiber on a daily basis for just four weeks has a significant effect on reducing perceived stress levels.

The men therehealthy diet

The news did not catch us by surprise. Over the last decade, an increasing number of studies have shown that diet can have a huge impact on our mental health. In fact, a healthy diet can even reduce the risk of many common mental illnesses.

The mechanisms underpinning the effect of diet on mental health have not yet been fully elucidated. It could be linked to the relationship 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 communicate constantly, enabling essential bodily functions such as digestion and appetite. It also implies that the emotional and cognitive centers in the brain are closely connected to our gut.

Onions, apples, bananas and oats against stress

Although previous research has shown that stress and behavior are also related to our microbiome, until now it was not clear whether changing our diet (and thus our microbiome) could have a different effect on stress levels.

In order to test this, in our study we recruited 45 healthy people with a relatively low fiber diet, between the ages of 18 and 59. More than half were women. The participants were divided into two groups and randomly assigned a diet to follow during the four weeks of the study.

A bowl of sliced ​​apples
Participants were instructed to eat foods rich in prebiotic fiber, such as apples.
gowithstock / Shutterstock

About half of them were put on a diet designed by nutritionist Kirsten Berding that would increase the amount of prebiotic and fermented foods they ate. This diet is known as “psychobiotic” because it includes foods that are associated with better mental health.

This group received individual education with a dietician at the beginning and in the middle of the study. They were instructed to include 6 to 8 daily servings of fruits and vegetables high in prebiotic fiber (such as onions, leeks, cabbage, apples, bananas, and oatmeal), 5 to 8 daily servings of whole grains, and 3 to 4 servings of legumes. week.

They were also asked to include 2-3 servings of fermented foods per day (such as sauerkraut, kefir and kombucha). Participants in the control diet received only general dietary advice, based on the healthy food pyramid.

The microbiota produces different substances

Interestingly, those on the psychobiotic diet reported feeling less stressed compared to those on the control diet. Likewise, there was a direct correlation between the strictness with which the participants followed 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 following the psychobiotic diet. Other studies have also shown that gut microbes are involved in sleep processes, which could explain this relationship.

The psychobiotic diet caused only subtle changes in the composition and function of gut microbes. However, we did see significant changes in the levels of certain 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-term and only among healthy people

Despite the encouraging results, our research is not without limitations. First, the sample size is small because the pandemic limited recruitment. Second, the short duration of the study may have limited the changes we observed, and it is not clear how long they would last. Therefore, long-term studies will be needed.

Third, although participants recorded their daily diet, this form of measurement may be subject to error and bias, particularly when assessing food intake. And while we did our best to make sure participants didn’t know which group they were assigned to, it’s possible they made a guess based on the dietary advice they received. This could have influenced the answers they gave at the end of the study.

Lastly, our work only included healthy people, so we don’t know what effect this diet might have on someone who isn’t so healthy.

However, our study provides strong evidence that changing your diet is an effective way to reduce stress in the long term. Adding to the evidence in this area of ​​research is the connection between diet, our microbiome and our mental health. It will be interesting to see if these results can also be replicated in people suffering from stress-related disorders such as anxiety and depression.

So the next time you’re particularly stressed, you might want to think more carefully about what you plan for lunch or dinner and include more fiber and fermented foods.

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