Mediation of adult fruit and vegetable consumption in the National 5 A Day for Better Health community studies.

BACKGROUND

The 5 A Day for Better Health community studies demonstrated in randomized trials the efficacy of population-based strategies to increase fruit and vegetable consumption in diverse geographic areas and settings.

PURPOSE

Mediation analysis can help to elucidate the theoretical basis of changing dietary habits. This is important for informing more powerful cancer prevention and control interventions to achieve broad public health impact.

METHODS

Five sites that focused on adults were included in mediation analyses to determine whether theoretically derived constructs assessed at baseline and follow-up contributed to explaining change in fruit and vegetable (F&V) consumption. These variables were knowledge, self-efficacy, and autonomy/responsibility. Stage of change also was considered as a potential moderating variable.

RESULTS

Self-efficacy and knowledge of the 5 A Day recommendation increased in those who received the interventions and were positively associated with higher F&V. Mediation of intervention effect was demonstrated for these variables. Autonomy/responsibility did not meet the criteria for mediation. There was no evidence of differential effect of mediators according to baseline stage.

CONCLUSIONS

The present study findings provide strong support for mediation of F&V consumption by two variables: self-efficacy and knowledge. The authors discuss the findings in relation to study limitations and future research directions.