# The Moderating Role of Dietary Quality and Dietary Fibre Intake on the Mood Effects of Positive Expressive Writing: A Pilot Study

## TL;DR

This pilot study found that better diet quality and higher fiber intake enhance the mood benefits of positive expressive writing.

## Contribution

The study is the first to show dietary factors moderate the psychological effects of expressive writing.

## Key findings

- Participants with better diet quality and higher fiber intake had greater increases in positive mood after positive writing.
- No significant changes in negative mood were observed across dietary conditions.
- Dietary factors may influence the gut–brain axis to enhance expressive writing effects.

## Abstract

Background: Positive expressive writing is associated with enhanced psychological wellbeing. Several individual differences are known to moderate the enhancement effects of positive expressive writing, but no studies to date have investigated the optimal dietary conditions under which expressive writing effects occur. In this pilot study, we sought to investigate whether diet quality and dietary fibre intake moderate the effects of positive writing on mood. Methods: The participants (12 males, 25 females, Mage = 33.0, SDage = 13.1) completed self-reported measures of dietary quality, dietary fibre intake, and positive and negative affect. They were then randomly allocated to complete either a positive expressive writing or neutral writing activity for 10 min. Positive and negative affect were measured again immediately after each activity. Results: Those participants who reported better diet quality and greater dietary fibre intake exhibited a significantly greater increase in positive affect following positive expressive writing relative to neutral writing. No significant effects were observed for negative affect. Conclusions: For the first time, we report that the effects of positive expressive writing on positive mood are enhanced under optimal dietary conditions. Further replication studies are needed to determine whether dietary factors can influence the conditions under which positive expressive writing benefits occur. We speculate that dietary influences on the gut–brain axis are a potential mechanism.