The study highlighted noteworthy differences in estimates of dietary supplement use and nutrient intake depending on the method used for assessment. For an industry where accurate measurement is central to research, monitoring and policy, the findings raise potentially impactful considerations.

“Valid dietary supplement (DS) assessment methods are critical for nutrition research and monitoring as DS contributes substantially toward micronutrient exposures for millions of Americans,” wrote researchers from Texas A&M University, Florida State University, NIH Office of Dietary Supplements, Tufts University and Wake Forest University.

The study compared two widely used dietary assessment tools: the Diet History Questionnaire-II (DHQII) and the Automated Self-Administered 24-hour Dietary Recall (ASA24).

Key findings from the IDATA study

The analysis involved 795 people between the ages of 50 and 74 participating in the Interactive Diet and Activity Tracking in American Association of Retired Persons (IDATA) cohort. Participants provided multiple dietary supplement reports using both methods. Results revealed significant variation in the reported prevalence of supplement use across product categories.

For instance, multivitamin use was reported by 21% of participants using ASA24 but only 3% with DHQII. Agreement between methods at the individual level ranged widely, and the authors noted, “prevalence of DS use varied by product type [13 of 28 comparisons differed in prevalence],” underscoring that the chosen tool strongly influenced estimates of supplement use.

Nutrient intake estimates also diverged between methods, particularly for vitamin D. Mean daily consumption amounts from supplements were 24–45 μg/day using ASA24, compared with 12–14 μg/day using DHQII, which the authors noted as a statistically significant difference.

“The choice of the DS measurement tool used is impactful for assessing total nutrient exposures [and] has implications for interpreting diet and health relationships and nutrition and monitoring,” the researchers concluded.

A focus on calcium and vitamin D reporting

Calcium and vitamin D were chosen as focus nutrients due to their high prevalence in supplement use and public health relevance. While calcium intake estimates were generally comparable between methods, patterns differed by sex.

Among female supplement users, calcium intakes were higher when reported through ASA24 compared with DHQII, but in contrast, “mean calcium intake per consumption day from DS did not vary between methods for males,” the study noted.

Vitamin D intake showed even greater discrepancies.

“In this IDATA analysis, the differences in mean vitamin D exposure amounts (i.e., the sum of the frequency of use and consumption day amount) from DS were particularly striking (∼45% difference in the mean amounts on the ASA24 compared with DHQII)“, the researchers wrote.

Across both sexes, ASA24 produced considerably higher estimates than DHQII, and “estimated mean consumption day amounts from DS among females was ∼771 mg/d from the ASA24, but only 679 mg/d from the DHQII,” highlighting that the magnitude of difference was more pronounced for women.

These findings suggested that differences in supplement reporting may not only depend on nutrient type but also on sex-specific usage patterns.

Key takeaways for industry stakeholders

For manufacturers and suppliers, the study underscored the importance of recognizing methodological differences in research that informs consumer trends, regulatory policy and product positioning. Divergent estimates of supplement use, particularly for widely consumed nutrients such as vitamin D, can influence how the industry understands market demand and health outcomes tied to supplementation.

The sex-specific differences in reporting add another layer of relevance. For companies developing gender-targeted formulations or evaluating usage data segmented by sex, these methodological discrepancies could shape market analysis and product innovation.

The authors also pointed to broader implications for research design, noting that “DS approaches beyond a questionnaire may be warranted for estimating absolute nutrient amounts.”

As supplement use continues to play a major role in nutrient exposure for U.S. adults, the IDATA study demonstrates that the method used to assess intake is not a neutral choice. For calcium and vitamin D in particular, both the nutrient and the demographic group studied can affect outcomes.

Source: The American Journal of Clinical Nutrition, 2025, 6, 121. doi: 10.1016/j.ajcnut.2025.03.020, “Methods matter for dietary supplement exposure assessment: comparing prevalence, product types, and amounts of nutrients from dietary supplements in the Interactive Diet and Activity Tracking in the American Association of Retired Persons cohort study”. Authors: Alexandra E Cowan-Pyle et al.