Comparison of national food supply, household food availability and individual food consumption data in Portugal

The present study aimed to compare Portuguese food and nutrient data retrieved from three distinct sources of dietary data: national food supply, household food availability and individual food consumption. In particular it was intended to validate the use of the dietary data derived from the Portuguese household budget surveys (HBS). The data sources used were food balance sheets (FBS) (1990, 1995 and 2000) generated by the Food and Agriculture Organization (FAO), HBS (1990, 1995 and 2000) collected by the National Statistics Institute (INE) and individual consumption obtained through a food frequency questionnaire (FFQ) applied in the context of the EpiPorto study circa 2000. Thirteen comparable food groups were established for analysis. Total energy, macro-nutrients and other selected dietary components were considered. The average daily values of different dietary sources were compared in absolute amounts (g/person per day) and in relative energy contribution (%E). To evaluate association and agreement between sources, Spearman's correlation coefficients and distance matrices based on Euclidian distances were computed. The obtained average daily per capita amounts reflect the different points of data collection in the food chain; HBS fall in the expected position, below FBS and closer to FFQ. Agreement between FBS, HBS and FFQ was higher when data were expressed in relative energy contribution than when absolute amounts were considered. In general, the observed discrepancies between the three data sources could be attributed to known differences in the methodological approaches. This study supports the finding that despite their constraints the HBS-derived data are a valid option to evaluate dietary habits in Portugal.