Gut-friendly diet reduces stress in APC Microbiome Ireland study

With the recognition of the involvement of the gut microbiota in brain processes, mental health and cognitive function, studies are emerging focusing on the impact of supplementation with prebiotics and probiotics as well as single food items (e.g., whole fruits or vegetables or fermented foods), demonstrating some promising results in modulating microbiome-host interactions.

But researchers from APC Microbiome Ireland wanted to look at the synergistic effect dietary components might have on microbiota diversity and composition as humans naturally consume a combination of food groups with every meal.

The goal of this study therefore was to investigate the potential of a "whole diet psychobiotic approach" - via the use of gut-friendly diet education sessions - to modulate the microbiota composition and affect feelings of stress and improve mood.

After conducting a four week study involving 45 adults, they concluded that just two diet education sessions worked to improve perceived stress in a healthy population, while eliciting specific metabolic changes in the gut microbiota.

Importantly, reduction in perceived stress was dose dependent, meaning that higher adherence to the study diet resulted in stronger decreases in the PSS score.

This is one of the first studies to investigate a psychobiotic diet approach to improve mental well-being in healthy adults.

"Given the fundamental influence of stress on the risk for developing other chronic diseases such as depression, these findings hold promise as potential therapeutic and preventative approaches," ​the report states.

"Thereby, using dietary and lifestyle approaches to address mental health concerns will become increasingly important and could become reflected in future dietary guidelines. ​

"Although our study provides one of the first data in the interaction between diet, microbiota and mental health, the subtle changes observed in biological outcomes and limited sample size highlights the necessity for future larger and longer duration studies to confirm the stress-alleviating effect of the psychobiotic diet."​

The study

This study was designed as a single-blind, randomized, controlled study. Healthy adult (male and female) participants with poor dietary habits, aged 18–59 years were recruited from the Cork area between February 2018 and November 2020.

Participants were block randomized (block of 4, stratified by gender) into either intervention (DIET) or control (CONT) group.

Poor dietary habits were determined via a dietary recall with a trained dietitian. At the initial screening visit, participants were screened for any psychiatric disorder using the MINI International Neuropsychiatric Interview (MINI) and demographic data were collected. Participants also completed the National Adult Reading Test (NART) as a brief measure of verbal IQ as well as the State-Trait Anxiety inventory to measure baseline anxiety levels.

The foods in focus of the psychobiotic diet included those known to influence the microbiota, namely, whole grains, prebiotic fruits and vegetables, fermented foods, and legumes while discouraging consumption of “unhealthy” foods such as sweets, fast food or sugary drinks.

The dietary intervention consisted of one 30-minute long education session (baseline) as well as a 15 minute (after 2 weeks) refresher session facilitated by a registered dietitian. During the first session, habitual dietary habits were assessed based on a 7-day food diary. Following this, participants were educated on the components of the study diet, which included consumption of fruits and vegetables high in prebiotic fibers (6–8 servings per day, e.g., onions, leeks, cabbage, apples, bananas, oats), grains (5–8 servings per day) and legumes (3–4 servings per week) as well as fermented foods (2–3 servings per day, e.g., sauerkraut, kefir or Kombucha). Advice also included strategies for meal planning, nutrition label reading, Irish food pyramid guidelines, and calorie guidelines.

A dietitian also facilitated the education for the control group and the session was matched in time and dietitian-contact to the diet intervention. A review of dietary habits was completed like the diet group; however, minimal input was provided and focused mainly on the HSE food pyramid. 

Questionnaire data (assessment of perceived stress and general health assessment) and collection of faecal, whole blood and urine samples was completed pre- and post-intervention. 

A dietary adherence score was calculated based on the ModiMedDiet score​.

Limitations of this study include the limited sample size, which was restricted due to the COVID-19 pandemic, as well as the short duration of the study, plus the fact diet records are susceptible to measurement error and bias in estimating food intake.

Source: Molecular Psychiatry​​​
https://doi.org/10.1038/s41380-022-01817-y​ 
"Feed your microbes to deal with stress: a psychobiotic diet impacts microbial stability and perceived stress in a healthy adult population"​
Authors: K. Berding, et al.