Reduction in vegetable intake disparities with a web-based nutrition education intervention among lower-income adults in Japan: Randomized controlled trial

Abstract

Background: No existing Web-based nutrition education interventions have been evaluated in light of socioeconomic status just in Japan. Objective: The aim was to investigate the effect of a Web-based intervention program on reducing vegetable intake disparities between low- and middle-income Japanese adults. Methods: In this randomized controlled trial, participants were assessed at three time points-baseline, postintervention (5 weeks later), and a follow-up after 3 months-from October 2015 to March 2016. We collected data via a Japanese online research service company from 8564 adults aged 30 to 59 years. Participants were stratified according to national population statistics for gender and age, and randomly selected. They were then randomly allocated into intervention (n=900) and control (n=600) groups such that both groups contained an equal number of individuals with low and middle income. The intervention program encouraged behavior change using behavioral theories and techniques tailored to their assumed stage of change. The outcome was vegetable intake servings per day (1 serving being approximately 70 g). Results: Out of 900 participants who started, 450 were from the middle income group (of which 386 or 85.7% completed the intervention), and 450 were from the low income group (of which 371 or 82.4% completed). In the intervention group, vegetable intake increased in the low-income participants from baseline to postintervention (0.42 servings, 95% CI 0.11-0.72). A two-way analysis of variance showed that low-income participants had significant main effects of group (η2=0.04, P=.01) and time (η2=0.01, P