Dietary supplements lead to reduced medical costs: Fact or wishful thinking?

To estimate the association between supplement use and reduced medical costs among Korean adults, using nationally representative data.

A population-based retrospective case-control study using difference-in-difference (DID) model with a propensity score weighting.

Data from the 2018-2020 Korea National Health and Nutrition Examination Survey (KNHANES) were merged with National Health Insurance Claims (NHIC) data for the years of 2017-2021. A total of 11,414 participants aged ≥19 years (6842 users vs. 4572 non-users) were selected. Outcomes included total medical costs, pharmaceutical costs, number of healthcare visits, hospitalizations and length of stay, measured in the year before and after supplement use. The double difference (β₃) captures changes in the outcome variables overtime among the user group, compared to the non-user group.

The DID estimates confirmed that supplement intake was not significantly associated with reduced medical costs. The results showed a tendency for supplement intake to increase total medical costs (β₃ = 21,149.01, p = 0.810), number of healthcare visits (β₃ = 0.016, p = 0.970), hospitalizations (β₃ = 0.033, p = 0.169), and length of stays (β₃ = 0.273, p = 0.304). However, the opposite tendency was found for prescribed drug costs (β₃ = -5329.60, p = 0.970). Nevertheless, no statistically significant associations were found for all outcomes.

Despite widespread use and popular belief, this population-based observational study did not show a statistically significant association between self-reported dietary supplement use and reduced medical costs among Korean adult. Further research is needed to provide evidence of the health benefits of dietary supplements, and regulatory authorities should promote evidence-based consumption of dietary supplements.