Consumption of Dietary Guidelines for Americans types and amounts of vegetables increases mean Subjective Happiness Scale scores: A randomized controlled trial

Abstract Background The health benefits of diets rich in fruits and vegetables (FV) are well established. Recent observational and intervention research suggests that FV consumption may also exert a positive effect on psychological well-being. Objective This study aimed to assess changes in mean Subjective Happiness Scale (SHS) scores in response to consuming DGA recommended types and amounts of vegetables. It was hypothesized that increased vegetable consumption would increase mean SHS scores. Design This study investigated a secondary outcome of a randomized, parallel, non-blinded controlled trial with a 1:1 allocation ratio to a provided vegetable intervention or attention control group. Participants/setting Men and women (n=75) aged 18-65 years, body mass index ≥25 kg/m2, with low habitual vegetable consumption were recruited from Grand Forks, ND, December 2016 to January 2018, for this community-based study. Intervention The vegetable intervention consisted of an 8-week feeding phase during which participants were provided with vegetables in DGA recommended types and amounts. The attention control group was not provided vegetables but completed the same testing schedule as the vegetable intervention group. Main outcome measure Mean SHS scores were assessed before and after the intervention. Statistical analyses Mean SHS scores were analyzed using a 2-way factorial mixed linear model analysis of variance. Results A significant interaction between treatment and visit (P=0.015) revealed greater mean SHS scores at week 8 than at baseline in the vegetable intervention group (+0.23 ± 0.11 (mean difference ± standard error of the difference) but no change in the attention control group (-0.15 ± 0.11). Conclusions Greater mean SHS scores were observed after increasing vegetable consumption to meet DGA recommendations, suggesting that adhering to DGA vegetable guidance may help promote psychological well-being.