Reproducibility of estimated nutrients intake collected by means of a dietary questionnaire

A food frequency questionnaire including 181 questions on 146 different foods and drinks was used in a multicentre case-control study on diet and gastric cancer recently carried out in Italy. A reduced set of questions (75), able to quantify at least 95% of the overall inter-individual variability of consumption of 11 nutrients, including calories, proteins, fats and carbohydrates, was determined using the data collected from 1623 population controls. For each nutrient, RRs estimates with the reduced set of nformation were similar to those obtained by means of the full questionnaire in the original study. 106 subjects (59 males and 47 females) were then randomly selected from the 661 controls recriuted in the centre of Florence and re-interviewed using the full questionnaire. The analysis suggests that a similar reproducibility for several nutrients can be obtained using a reduced questionnaire.