Nutrient Deficiency Classification Bias Relating to the 24-hour Dietary Recall: A Case Study With Dietary and Red Blood Cell Folate

Abstract

SAB3-PD-07 The 24-hour recall data from food consumption surveys, such as the U.S. Continuing Survey of Food Intake by Individuals (CSFII) or the NHANES, are frequently used to estimate dietary exposure, which is often compared with recommended daily intake (RDI) for micronutrient to classify “nutrient deficiency status” for various population subgroups. However, the 24-hour recall method is not ideal for estimating long-term average daily food intakes since there are considerable variations in day-to-day intake of food within individuals. Single-day intake data usually result in a distribution that is flatter and wider than the true distribution of usual intakes of individuals in the population. Thus, the prevalence of high or low intakes (undernutrition or overnutrition) is overestimated with single 24-hour recall. The U.K. National Diet and Nutrition Surveys collect multiple days of intake data and could provide a mean to quantify the effects of intra-individual variation on estimates of usual food intakes. Individual's dietary folate intakes for day 1 through day 7 are estimated and folate status is established based on different combination of intake days and number of days prior to blood sampling. Using the red blood cell folate data collected in the U.K. survey, individual's folate deficiency status is also defined. Red blood cell folate concentration is thought to be a better index of tissue folate storage than serum folate, ie, longer-term measure of folate status. Classification of folate deficiency status based on the dietary intake estimates is compared with classification based on RBC folates. Bias in the classification of folate status using the single 24-hour recall is discussed.