Link between diet, gut microbiome diversity, and mental health: Shifting to vegetarian, Mediterranean, and ketogenic diets improves mood and reduces anxiety

*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

A team of US-based scientists has found a connection between diet, gut microbiota, and mental health in adults. They have shown that while higher fat and protein consumption improves mental well-being, higher carbohydrate consumption increases stress, anxiety, and depression.

The study is currently available on the medRxiv preprint* server.

Study: The Role of Diet on the Gut Microbiome, Mood and Happiness. Image Credit: Marian Weyo / Shutterstock

Background

The human gut microbiota is a collection of microorganisms residing symbiotically inside the gastrointestinal tract. The gut microbiota predominantly comprises bacteria belonging to three major phyla, Firmicutes, Bacteroidetes, and Actinobacteria.

Diet is one of the main drivers for maintaining gut microbiota composition and diversity. In normal physiological conditions, the gut microbiota is vital in regulating various important biological functions, including immune, metabolic, and neuropsychiatric functions. However, any alteration in gut microbiota composition (dysbiosis) can lead to inflammatory diseases and infections.    

In the current study, scientists have explored the relationship between diet, gut microbiota, and mental health. Their main hypothesis is that the diet's nutrient composition influences gut microbiota diversity and distribution, which in turn impact the measures of mental well-being.

Study design

The study was conducted on 20 adult individuals who had maintained a consistent and unchanging diet for at least three days before the study enrollment.

The participants were asked to record their diet for two consecutive days, sample their gut microbiota using the kit provided, and complete five validated surveys of mental health, mood, happiness and well-being.

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After baseline data collection, the participants were subjected to a diet change for a minimum of one week. Afterward, they were asked to repeat the diet recording, microbiome sampling, and five surveys.

Important observations

The majority of participants reported following a Western diet without prebiotics or probiotics at the baseline. During the study period, most participants chose a vegetarian diet plan, followed by ketogenic and Mediterranean diets.

No significant changes in fat, carbohydrate, and protein intakes were observed between the baseline diet and study-period diet. However, a reduction in total calorie and fiber intakes was observed in the study-period diet compared to the baseline diet.

The diet during the study period caused significant alterations in the measures of anxiety, well-being, and happiness. However, no change in gut microbiota diversity was observed because of the diet change.

Relationship between gut microbiota diversity, mental health, and dietary composition

The comparison between dietary composition and mental health revealed that a higher percentage of fat and protein intake due to diet change improves mental well-being and reduces anxiety and depression.

In contrast, a higher carbohydrate consumption due to the diet change led to reduced mental well-being and increased anxiety and depression.

The comparison between dietary composition and gut microbiota revealed that a reduction in total calorie and fat intake due to the diet change results in induction in gut microbiota diversity.

Further analysis revealed that the participants with more diverse gut microbiota experienced less anxiety and depression.

Study significance

The study finds a link between dietary composition, gut microbiome diversity, and mental health in adult individuals. Specifically, the study shows that while fat and protein consumption improves mental well-being, carbohydrate intake has the opposite effect.

The study also states that less consumption of calories and fiber can lead to a more diverse gut microbiome, reducing anxiety and depression.

As mentioned by the scientists, the study opens a new path for future research to more conclusively understand how specific dietary components may help minimize anxiety and depression at the individual level.

*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Dr. Sanchari Sinha Dutta

Dr. Sanchari Sinha Dutta is a science communicator who believes in spreading the power of science in every corner of the world. She has a Bachelor of Science (B.Sc.) degree and a Master's of Science (M.Sc.) in biology and human physiology. Following her Master's degree, Sanchari went on to study a Ph.D. in human physiology. She has authored more than 10 original research articles, all of which have been published in world renowned international journals.