Interpretation of data on dietary intake.

Although this discussion has focused on the interpretation of dietary data, assuming that it is representative of actual and usual intake and that the nutrient analysis based on it involved the use of up-to-date food composition tables, the readers should be sensitive to other potential sources of error or bias in obtaining information on food and/or nutrient intake. These include errors due to irregularity of food consumption, under- or overreporting of intake, errors in reporting either the amount or the description of the food consumed, recording errors on the part of the interviewer or coding errors on the part of the coder, limitations in the tables of food composition due to missing data for certain nutrients in certain foods or to biologic variability in the same foods from different sources or in those marketed under different conditions, imputed values, the unknown composition of formulated foods or foods prepared from home or commercial recipes, differences in bioavailability of nutrients as a function of the diet, or the use of abridged tables of food composition. In spite of the many unresolved issues relating to dietary standards and the interpretation of dietary intake data, we are still able to make a reasonable assessment of dietary adequacy of groups and individuals with our current system, which is viewed as a unique federal resource. It is hoped that the eventual passage of the National Nutrition Monitoring and Related Research Act will provide both the impetus and the resources to permit us to develop a more sophisticated system for assessing both food intake and nutritional status.