Food Diversity and Validity of Semiquantitative Food Frequency Questionnaire

Abstract

We hypothesized that validity of semiquantitative food frequency questionnaire would be affected by food diversity (variety of foods consumed), because greater food diversity may be related to greater within-individual variation of nutrient intake, which can attenuate the correlation coefficient measuring validity of the questionnaire. We obtained 12 one-day diet records over one year and responses to a semiquantitative food frequency questionnaire from 37 subjects. The food diversity score for each subject was determined by the total number of different foods consumed during the 12 days for the diet records, and the subjects were divided into two groups according to the score. The within-individual variances were similar in those with higher and lower food diversity scores. We never observed a significantly lower correlation coefficient for any nutrient in those with higher food diversity scores. The observed and corrected correlations for most of the micronutrients were higher in those with higher food diversity scores, and the differences were statistically significant for crude fiber, vitamin C, iron, and potassium. The validity of the semiquantitative food frequency questionnaire did not appear to be lowered greatly by greater food diversity.J Epidemiol, 1998 ; 8 : 297-301.semiquantitative food frequency questionnaire, diet record, within-individual variation, betweenindividual variation, validityNumerous studies have been devoted to the methods of measuring an individuals' usual dietary intake1-4). Currently, semiquantitative food frequency questionnaires (FFQs) are commonly used to obtain estimates of individuals' dietary intake and to relate diet to the development of various diseases. There is no gold standard for directly assessing the validity of dietary assessment methods. However, the validity of the semiquantitative FFQs is often determined by comparing data derived from them with those obtained from diet records (DRs) or 24-hour recalls 5). Because of day-to-day variation in an individual's food intake, memory lapses, misinterpretation, and restriction by a fixed list of foods, it is difficult to assess a usual diet accurately using a semiquantitative FFQ. One of the characteristics of diet among the Japanese in the present day may be food diversity. We hypothesized that a more varied diet should be related to a low validity of semiquantitative FFQ. It is possible that a more varied diet is related to a large within-individual variation in nutrient intake.The ratio of the within-individual to between-individual variance is used as an index of bias and power loss in etiological studies of disease S). A large ratio reduces the strength of any association. A large within-individual variation can distort the correlation coefficient.Our hypothesis implies that food diversity makes it difficult to develop a semiquantitative FFQ with high validity to assess the diet among the Japanese. To examine our hypothesis, we analyzed data from 12 one-day DRs over one year and responses to a semiquantitative FFQ.

A meta-analysis of the reproducibility of food frequency questionnaires in nutritional epidemiological studies

“…Obtaining an accurate estimate of long-term habitual food intake is crucial [3], which is very important to better understand diet and associated diseases. However, assessment of nutritional habits is complex [4], and they are affected by real changes in regular dietary intake and random changes in FFQ [5,6]. FFQs allow covering a wider range of foods, including those consumed rarely, and can be administered once whereas to describe usual dietary habits with a reasonable reproducibility [7].…”

Validity of the Responses to Self-administered Questionnaires as Compared with the Responses to Interviews Using a Structured Questionnaire

“…In most epidemiological studies, information on life style factors such as diet and nutritional intake, smoking and drinking habits or physical activity is quite frequently obtained by an interview using a structured questionnaire or by means of a self-administered questionnaire. In Japan there have been several studies that evaluated the reproducibility [1,4] of a self-administered questionnaire using the same questionnaire twice or evaluated the validity [1][2][3][4] With this in mind we conducted the present study, using the subjects from a case-control study of hepatocellular carcinoma [5,6], to evaluate the validity of self-administered questionnaires about smoking and drinking habits by comparing the responses with those from interviews using a structured questionnaire that was used in the case-control study and which included questions about changes in smoking and drinking habits over time.…”