Abstract
BACKGROUND: Dietary diversity is an important component of dietary quality. The Nutrient Composition Diversity Index (NCDI) is a dietary diversity metric that quantifies dissimilarity among foods in a diet based on nutrient content. Research has yet to assess NCDI using an extensive food composition database and repeated 24-h dietary intake data or to test its associations with other aspects of dietary quality among United States adults. OBJECTIVES: This study aimed to describe NCDI constructed from dietary data collected over 2 quantitative 24-h recalls in a sample of healthy United States adults and to assess its relationships with adherence to the Dietary Guidelines for Americans and micronutrient intake adequacy. METHODS: We analyzed cross-sectional dietary data from 377 participants (strata balanced for sex, age, and body mass index). Individual NCDI was scored using a dendrogram of 5628 foods and 30 nutrients from USDA food composition tables. We calculated usual NCDI to account for within-person dietary variability. Mean-standardized usual NCDI was compared with the 2015 Healthy Eating Index (HEI)-2015, HEI-2015 dietary components, and mean probability of adequacy for 17 vitamins and minerals in linear regression models, and with nutrient intakes using Pearson correlations. RESULTS: Mean usual NCDI for the sample was 2.1% (standard deviation: 0.60), with an observed range of 0.81% to 4.0%; 70% of participants scored in the same or adjacent quintile of individual NCDI for their 2 recalls. NCDI was positively associated with HEI-2015 and with several HEI component scores while adjusting for total HEI-2015 (P < 0.0001). NCDI was also positively associated with nutrient intakes and with mean probability of adequacy in bivariate and energy-adjusted models (P < 0.0001). CONCLUSION: NCDI measures the dissimilarity dimension of dietary diversity and shows expected day-to-day variability and associations with adherence to Dietary Guidelines for Americans and micronutrient intake adequacy.