The Development of the Total Nutrient Index

Alexandra Elizabeth Cowan, Purdue University

Abstract

Dietary supplement (DS) use is highly prevalent in the U.S. and can contribute substantial amounts of micronutrients to the one-half of U.S. adults and nearly one-third of U.S. children who use them. Despite their pervasive use, the best practices for assessing the prevalence of use of and measuring nutrient intakes from supplemental sources remain largely unknown, and currently no metric designed to assess total micronutrient exposures from foods, beverages, and DS exists. Comprehensive and robust methods for assessing the prevalence of use of and nutrient intakes from DS are critical for population-level research and surveillance.Therefore, the overarching aims of the research presented in this dissertation were to 1) identify the most comprehensive method for assessing the prevalence of use of and estimating nutrient intakes from DS, 2) characterize DS use and examine trends in overall and micronutrientcontaining DS use among the U.S. population using multiple modes of DS assessment, 3) develop the first micronutrient-based diet quality index designed to capture usual intakes from all sources of under-consumed micronutrients among the U.S. population (i.e., the Total Nutrient Index (TNI)) and 4) to determine if the TNI is a useful measure for assessing total micronutrient exposures among the U.S. adult population.National Health and Nutrition Examination Survey (NHANES) 2011-2014 data among U.S. adults were employed to evaluate four combinations of methods constructed from two data collection instruments (i.e., the 24-hour dietary recall (24HR) and the NHANES in-home inventory with a frequency-based DS prescription medicine questionnaire (DSMQ)) for measuring the prevalence of use of and amounts of selected nutrients from DS. The results from the analysis indicated that a higher prevalence of DS use is reported when using frequency-based methods, like the DSMQ, but higher nutrient amounts are reported on the 24HR. Thus, combining the DSMQ with at least one 24HR (i.e., DSMQ or ≥1 24HR) provides the most comprehensive approach for measuring DS use and estimating nutrient intakes from supplemental sources among U.S. adults.Differences in the estimated prevalence of use of DS on the DSMQ or ≥1 24HR as compared with the DSMQ only were also noted among a nationally representative sample of the U.S. population from the 2007-2018 NHANES. When characterizing DS use and examining trends in overall and micronutrient-containing DS use among the U.S. population using multiple modes of DS assessment, increases in both overall and micronutrient-containing DS use were observed over time, but the prevalence of use was lower on the DSMQ than the DSMQ or ≥1 24HR among the total population and across all population subgroups. Therefore, the findings from this study were congruent with our previous analysis and contributed to a growing body of literature that utilizes multiple methods of DS assessment to improve the comprehensiveness of DS exposure assessment.The insights garnered from identifying the most comprehensive method for approximating micronutrient intakes from supplemental sources were implemented in the development and initial application of the first micronutrient-based diet quality index designed to capture usual intakes from all sources of under-consumed micronutrients among the U.S. population, named the TNI.

Degree

Ph.D.

Advisors

Bailey, Purdue University.

Subject Area

Agriculture|Public health|Medicine|Nutrition|Pharmaceutical sciences

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