Comparison of estimated nutrient intake by two methods: validation of a food frequency questionnaire

The validity of a quantitative self-administered food frequency questionnaire (FFQ) was tested by comparison with 7-d weighed food records (7DWR). Subjects for the study were 24 females between 20 and 43 years of age (mean = 24 years). The main aim of the FFQ was to classify subjects according to their total fat intake.
The mean nutrient intakes estimated by the FFQ were consistently and significantly higher than the estimates by the 7DWR. Rank correlations showed that the FFQ was able to rank subjects similarly for total energy intake, fat, alcohol and fibre intake as well as for the percentage contribution of macronutrients to energy intake. Intra-class correlations showed that the two methods did not agree at the individual level for energy and macronutrient intake except alcohol. These results suggest that the FFQ was suitable for ranking the subjects according to their total fat intake but was not suitable for estimating the individual nutrient intake or average nutrient intake of this relatively small group.