Creating default codes and assigning nutrient values for non-specific dietary supplements

Capturing dietary supplement intake is difficult when the participant provides insufficient detail. The purpose of this project was to assign default nutrient values to incompletely reported dietary supplements. From 1999 to 2001, all participants in the Hawaii-Los Angeles Multiethnic Cohort were sent a questionnaire requesting information on use of multivitamins or multivitamins with minerals. In Hawaii, 70,058 supplements were reported by 44,662 respondents. If the supplement reported could not be matched to a specific supplement on the market, one of 529 defaults was assigned. The defaults were designed to capture as much detail as possible about the reported supplements. Nutrient values were assigned to each default after data entry was completed. We determined all multivitamins and multivitamins with minerals that were used and the frequency of each. Using this information, each default was linked to appropriate supplement(s) and nutrient values were calculated using a weighted average, determined by the frequency of each linked supplement. When the supplement reported cannot be matched to a supplement on the market, the use of default nutrient values provides a better estimate of nutrient intake than assuming no supplement was consumed.