Dietary Supplement Items on Commonly Used Food Frequency Questionnaires

Abstract

For some nutrients, dietary supplements (DS) contribute substantially to total intakes, and thus assessment of DS use is important. Most large epidemiological studies use food frequency questionnaires (FFQ) to obtain information about DS intake. However, the various FFQs enquire about different DS and use differing methods for assigning values for nutrients and other bioactive constituents in the products. In addition, FFQs differ in the questions about frequencies, duration and dosages of DS, making comparisons of intakes across studies difficult. Inconsistencies in the literature relating DS usage with particular outcomes may be partly due to differences in assessment of DS in these questionnaires. We examined commonly used FFQs available for general use in large epidemiological cohorts including the Diet History Questionnaire II, the Willett questionnaire, the Block questionnaire 2014 full‐length FFQ + physical activity screener, the Women's Health Initiative FFQ, the Vitamins and Lifestyle FFQ and the Multiethnic Cohort Study FFQ and their additional supplement questionnaire used to validate their FFQ supplement data. In addition to the studies mentioned, these questionnaires have been used in large prospective studies including the Nurses' Health Study, the Health Professionals Follow‐Up Study, the Women's Health Study, the Sister Study, the Cancer Prevention Study II Nutrition Survey, and the AARP cohort study. This analysis compared differences and similarities on items querying DS use. The FFQs differed on number of DS with lists varying from 3 to 49 supplements; type of supplement (e.g. One FFQ did not ask about multivitamin with minerals, four did not ask about herbal/botanical, and two did not ask about non‐vitamin/non‐mineral supplements); dosages (Six of the FFQs asked for dosages only for specific nutrients such as vitamin C, vitamin E, vitamin D, and calcium); and frequency and duration categories of use (e.g. Two FFQs did not ask how often DS are used, two asked for seasonal use only for vitamin A, C and D, and only four asked how often herbal/botanical supplements are used). Information on the DS database used to estimate nutrients from supplements on FFQs was also obtained. In summary, all FFQs included questions to determine the use of multivitamins, single vitamins, and single minerals, but differed in the inclusion or exclusion of other types including multivitamins with minerals or other combinations, herbal/botanical, and non‐vitamin/non‐mineral supplements. Moreover, FFQs differed in the number of DS supplements listed, dosage for all DS listed, and frequency and duration of use for some of the DS including herbal/botanical supplements.Support or Funding InformationOffice of Dietary Supplements, NIH