New Tool Developed at the University of Minnesota to Assess Use of Dietary Supplements

By Lisa Harnack, Dr.P.H., M.P.H.
Associate Professor
Division of Epidemiology and Community Health
University of Minnesota School of Public Health

Over the past decade the availability and use of dietary supplements has dramatically increased.  Approximately 40 percent of U.S. adults currently use one or more dietary supplement. As a result of this trend, it has become imperative that both food intake and supplement use be assessed in studies measuring an individual’s nutrient intake.  If supplement use is not accounted for, the magnitude of measurement error that may result is substantial, with nutrient intake estimates not off by an “inch” but rather a “mile” for supplement users. 

Unfortunately the best methodologies for assessing nutrient intake from foods, 24-hour dietary recalls, and food records are not well suited to assessing use of supplements, which are more akin to pharmaceuticals than foods.  To address this conundrum, the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) is providing funds to the University of Minnesota Nutrition Coordinating Center (NCC) to develop a tool for assessing dietary supplement use that may be used in combination with the collection of a 24-hour dietary recall. 

Dietary Supplement Assessment Tool

The dietary supplement assessment tool being developed by NCC is designed to work in conjunction with Nutrition Data Systems for Research (NDSR) software.  NDSR, which is used by hundreds of nutrition researchers across the country, allows for direct data entry and fully automated coding of interviewer-administered, 24-hour dietary recalls.  NCC (a non-profit organization housed in the School of Public Health’s Division of Epidemiology and Community Health) developed this software.  Dr. Lisa Harnack, an SPH associate professor and assistant director of NCC, has led the development work for this new tool.  To ensure the tool is optimally developed, researchers utilized the expertise of Drs. Margaret Artz from the School of Pharmacy and Joseph Konstan from the Department of Computer Science and Engineering during the design phase.

In developing the tool, the research team was first confronted with the need to devise an approach to assessing dietary supplement use that would be valid and feasible for use in population-based studies where participant burden must be kept in check.  It was decided that the medication inventory method commonly used in pharmaceutical research should serve as the basis for the assessment approach.  In adapting this interviewer-administered approach for use in assessing dietary supplements, a tiered structure was designed that involves first screening for use of dietary supplements, then collecting product detail (e.g. full name of product, number of times taken, etc.), and finally reviewing the information collected to allow for corrections and additions.

Demonstration Study

A demonstration study has been conducted to evaluate the dietary supplement assessment tool, with results indicating it is generally acceptable to both participants and interviewers.  Collecting dietary supplement use information was found to require a reasonable amount of time for most demonstration study participants who reported using dietary supplements (5-10 minutes).  However, the time required was substantial for those who reported using a large number of products.  For example, the time required to complete assessments for those who reported using 10 or more products was generally greater than 30 minutes.  

The dietary supplement tool will be released with the 2007 version of NDSR, providing researchers with an avenue for assessing nutrient intake from both food and supplemental sources.  Next steps include conducting a validation study to determine whether the tool results in accurate estimation of nutrient intake from supplemental sources.