The effect of fruit and vegetable consumption on psychological wellbeing in young adults

Abstract

Background: Consumption of fruits and vegetables (FV) is not only linked with lower incidence of mental illness, but also indicators of positive well-being such as life satisfaction, optimism, and happiness – suggesting a broad impact of nutrition on psychological health. The aim of the current project was to test whether this relationship is causal. Methods: Young adults (n=171) were randomly assigned into a diet-as-usual control condition, an Ecological Momentary Intervention condition (receiving text message reminders to increase their FV consumption), or a Fruit and Vegetable condition (receiving two additional daily servings of FV to eat). This RCT tested, (a) the effectiveness of two intervention strategies in increasing daily FV consumption compared to control, and (b) whether increases in FV consumption were associated with improvements in positive well-being including, flourishing, vitality, and eudaimonic behaviours (curiosity, creativity, and motivation). These were assessed nightly for two weeks using a smartphone-accessed survey. Blood samples testing two biomarkers – vitamin C and carotenoids – were taken pre- and post-intervention and psychological expectancies were assessed as potential mediators. Findings: Only those given extra FV to consume reported increased daily flourishing, vitality, and eudaimonic behaviours relative to the other groups. These benefits were not mediated by biomarkers or psychological expectancies. Discussion: This is the first study to show that being provided with extra servings of FV can result in short-term improvements to higher-order states of wellbeing associated with engagement, fulfilment, and curiosity in life. This highlights dietary change as a promising adjunct in promoting psychological well-being.