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 2010-2015 Dietary Guidelines for Americans (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, nonblinded 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 to 65 years, body mass index ≥ 25, with low habitual vegetable consumption were recruited from Grand Forks, North Dakota, 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 = .015) revealed greater mean SHS scores at week 8 than at baseline in the vegetable intervention group (+0.23 ± 0.11) (mean difference ± SE 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.

Keywords: Dietary Guidelines for Americans; Fruits and vegetables; Happiness; Psychological well-being; Vegetable consumption.