Does fruit and vegetable consumption impact mental health? Systematic review and meta-analyses of published controlled intervention studies.

Associations between fruit and vegetable (FV) consumption and mental health are suggested, largely from observational studies. This systematic review aimed to identify and summarise all published controlled intervention studies investigating the effects of FV consumption on mental health in adults. Four academic databases (Medline, PsycINFO, PubMed, Web of Science) were searched on 16 September 2022, over all years, for studies that used an intervention design; included FV consumption; included an appropriate non-FV-consumption control; used a validated measure of mental health and were conducted in healthy adults or adults with solely a depressive or anxiety-related condition. Study details were tabulated and combined using meta-analyses. Risk of bias was assessed using the domains of the Cochrane Collaboration. Six studies, enrolling 691 healthy adults and reporting on one or more mental health outcomes, were found. Meta-analyses found small and imprecise effects of FV consumption for: psychological well-being (4 studies, 289 participants) standardised mean difference (SMD) = 0·07 (95 % CI -0·17, 0·30), P = 0·58, I2 = 0 %; depressive symptomology (3 studies, 271 participants) SMD = -0·15 (95 % CI -0·40, 0·10), P = 0·23, I2 = 47 % and anxiety-related symptomology (4 studies, 298 participants) SMD = -0·15 (95 % CI -0·39, 0·08), P = 0·20, I2 = 71 %. Some benefit for psychological well-being was found in change-from-baseline data: SMD = 0·28 (95 % CI 0·05, 0·52), P = 0·02, I2 = 0 %. Risk of bias was high in many studies. Limitations include the consideration only of published studies and stem from the studies found. Given the few, limited studies available and the small size of effects, stronger evidence is needed before recommending FV consumption for mental health.

Protocol: The effects of nutrient- vs food- vs food-substitution-based dietary recommendations for reducing free sugar intakes, on free sugar intakes, dietary profiles and sweet taste outcomes: A randomised controlled trial.

BACKGROUND: Dietary guidelines are intended to inform and aid the general public, with the aim of improving healthy diets and reducing health risk. The effectiveness of these guidelines, however, is rarely investigated. AIM: This work investigates the effects of three different types of dietary recommendations for reducing free sugars, on free sugar intakes over 12 weeks. Secondary aims will also investigate how these different recommendations affect secondary outcomes, outcomes in subsets of the trial population, and identify barriers and facilitators to dietary change. METHODS: Using a randomised controlled parallel-group trial with three intervention and one control arms, 240 individuals consuming >5% total energy intake from free sugars will be randomized to receive: nutrient-based, nutrient- and food-based, nutrient-, food- and food-substitution-based recommendations or no recommendations, with outcomes assessed for the following 12 weeks. Our primary outcomes are free sugar intakes and adherence to the recommendations. Secondary outcomes are daily energy intake, dietary composition, anthropometry, sweet food perceptions and preferences, sweet food choice, attitudes towards sweet foods, eating behaviour and food choice, knowledge and lifestyle variables, quality of life, adverse events, and barriers and facilitators towards intervention adherence. RESULTS: Data will contribute to three distinct analyses: 1) Analyses to investigate the effects of the three different dietary recommendations versus control; 2) Analyses of the effects of the dietary recommendations in different population subgroups, and 3) Investigation of the barriers and facilitators to success. CONCLUSION: This work offers new perspectives on the effects of different dietary recommendations to enact behaviour change.