Describing socioeconomic gradients in children's diets - does the socioeconomic indicator used matter?

Background: Children of low socioeconomic position (SEP) generally have poorer diets than children of high SEP. However there is no consensus on which SEP variable is most indicative of SEP differences in children's diets. This study investigated associations between diet and various SEP indicators among children aged 9-13 years. Method: Families (n = 625) were recruited from 27 Adelaide primary schools in 2010. Children completed semi-quantitative food frequency questionnaires providing intake scores for fruit, vegetables, non-core foods, sweetened drinks, and healthy and unhealthy eating behaviours. Parents reported demographic information by telephone interview. Differences in dietary intake scores were compared across parental education, income, occupation, employment status and home postcode. Results: Across most SEP indicators, lower SEP was associated with poorer dietary outcomes, including higher intake of non-core foods and sweetened drinks, and more unhealthy behaviours; and lower intake of fruit and vegetables, and fewer healthy behaviours. The number and type of significant SEP-diet associations differed across SEP indicators and dietary outcomes. Mother's education appeared most frequently as a predictor of children's dietary intake, and postcode was the least frequent predictor of children's dietary intake. Conclusion: Socioeconomic gradients in children's dietary intake varied according to the SEP indicator used, suggesting indicator-specific pathways of influence on children's dietary intake. Researchers should consider multiple indicators when defining SEP in relation to children's eating.