The effectiveness of nutrition interventions on dietary outcomes by relative social disadvantage: a systematic review.

OBJECTIVE: To determine whether nutrition interventions widen dietary inequalities across socioeconomic status groups.
DESIGN: Systematic review of interventions that aim to promote healthy eating. DATA SOURCES: CINAHL and MEDLINE were searched between 1990 and 2007. REVIEW
METHODS: Studies were included if they were randomised controlled trials or concurrent controlled trials of interventions to promote healthy eating delivered at a group level to low socioeconomic status groups or studies where it was possible to disaggregate data by socioeconomic status.
RESULTS: Six studies met the inclusion criteria. Four were set in educational setting (three elementary schools, one vocational training). The first found greater increases in fruit and vegetable consumption in children from high-income families after 1 year (mean difference 2.4 portions per day, p<0.0001) than in children in low-income families (mean difference 1.3 portions per day, p<0.0003). The second did not report effect sizes but reported the nutrition intervention to be less effective in disadvantaged areas (p<0.01). The third found that 24-h fruit juice and vegetable consumption increased more in children born outside the Netherlands ("non-native") after a nutrition intervention (beta coefficient = 1.30, p<0.01) than in "native" children (beta coefficient = 0.24, p<0.05). The vocational training study found that the group with better educated participants achieved 34% of dietary goals compared with the group who had more non-US born and non-English speakers, which achieved 60% of dietary goals. Two studies were conducted in primary care settings. The first found that, as a result of the intervention, the difference in consumption of added fat between the intervention and the control group was -8.9 g/day for blacks and -12.0 g/day for whites (p<0.05). In the second study, there was greater attrition among the ethnic minority participants than among the white participants (p<0.04).
CONCLUSIONS: Nutrition interventions have differential effects by socioeconomic status, although in this review we found only limited evidence that nutrition interventions widen dietary inequalities. Due to small numbers of included studies, the possibility that nutrition interventions widen inequalities cannot be excluded. This needs to be considered when formulating public health policy.