Rationale, design, and analysis of combined Brazilian household budget survey and food intake individual data

BACKGROUND Data on food intake at the individual level and its statistical distribution in population groups defined by age, gender, or geographic areas are important in planning public health and nutrition programs. However, individual-based surveys in representative population samples are expensive to perform. METHODS/DESIGN In Brazil, an individual based survey is under consideration to be conducted alongside the household budget survey (HBS), which will be carried out in 2008-2009. This paper presents the methodological framework of dietary data collection and indicates the directions to combining both sources of data. The 2008-2009 Brazilian HBS sample will include 60,000 households. Of the selected HBS households, 30% will be randomly sampled to gather data on individual food intake. Therefore, individual dietary intake data is expected to be gathered for 70,000 individuals. Data collection procedures will comprise: completion of a diary with information regarding food purchases during a seven-day period; registration of all items consumed during two non-consecutive days for all 10 year-old or older members of the household. The sample will be large enough to capture the variation between individuals, and the two records will assure the estimation of the variation within individuals for food groups, energy and nutrients. Data on individual dietary intake and food family budget will be stratified by the five regions of the country and by rural or urban. A pilot study has been conducted in two states, and it indicated that combining individual and budgetary data in a survey is feasible. DISCUSSION This kind of study will allow us to estimate correlations between individual intake and household purchases, overcoming the limitations of individual dietary surveys, and enhancing the HBS with information on eating out and intra-familiar distribution of food.