Relative validity and reproducibility of a diet history questionnaire in Spain. II. Nutrients. EPIC Group of Spain. European Prospective Investigation into Cancer and Nutrition.

BACKGROUND: A pilot study was carried out to evaluate the relative validity and reproducibility of a dietary history questionnaire (DH) administered by interview and designed to be used in a prospective study on diet and cancer.
METHODS: The DH was administered twice, with a year's interval, to 91 volunteers of various occupational categories, aged 35-60 years, of both sexes. Twelve 24-hour recalls applied monthly during the year between the two administrations of the DH were used as a reference method.
RESULTS: Mean values of daily intake between the two methods were very similar for most nutrients. The DH tended to underestimate intake, compared to the 24-hour recall, for some nutrients like saturated fat and dietary fibre in males and saturated and polyunsaturated fat, cholesterol and retinol in females. It tended to overestimate intake of vitamin C, retinol and beta-carotene in males and dietary fibre, vitamin C and beta-carotene in females. Pearson correlation coefficients between the daily intake of nutrients based on the mean of the 12 24-hour recalls and the second use of the DH showed most values to be > 0.80 in males (ranging from 0.28 for retinol to 0.89 for energy, lipids, mono and polyunsaturated fat) and 0.60 in females (ranging from 0.33 for cholesterol to 0.83 for alcohol). For the great majority of nutrients studied, more than 80% of the subjects classified in the two highest quintiles and in the two lowest quintiles according to the DH2 which coincided with the highest and lowest quintiles of the classification according to the average of 24-hour recalls.
CONCLUSIONS: The DH method provides quite good information on the habitual nutrient intake of the individual in a recent 1-year reference period.