Accepted for/Published in: Interactive Journal of Medical Research
Date Submitted: Aug 19, 2025
Date Accepted: Feb 11, 2026
Prevalence and associated factors of excessive dietary supplement use among Japanese adults: cross-sectional study
ABSTRACT
Background:
The use of dietary supplements (DSs) can lead to an excessive intake of certain nutrients, posing potential health risks. However, studies are scarce on whether DS users adhere to recommended doses provided by the manufacturer and what factors are associated with overconsumption of DS.
Objective:
By leveraging purchase history data to estimate DS use precisely, this study aimed to investigate the factors associated with DS consumption exceeding manufacturer-recommended doses and examine the prevalence of excess nutrient intake among DS users.
Methods:
An online survey was conducted from November to December 2024 among 2,002 adults (aged 18–74 years) with a history of buying one of the 25 major DS products and who had used it in the previous month or regularly. Self-reported daily DS consumption was assessed using a questionnaire and compared to the manufacturer-recommended doses indicated in the package. Using multivariate logistic regression analysis, the associations between DS consumption exceeding the manufacturer-recommended doses and sociodemographic factors were examined.
Results:
The prevalence of DS users exceeding Tolerable Upper Intake Levels (ULs), defined according to the Dietary Reference Intake for the Japanese, was calculated based on vitamin and mineral intake from DS only. Consequently, 371 participants (18.5 %) consumed DS above the manufacturer-recommended dose. Consumption of DS above the recommended dose was associated with older age, part-time or full-time employment, use of tablet-form DS, especially single water-soluble vitamin tablets, use of DS for 6 months or more, and intentional consumption above the recommended dose. For the DS containing nutrients with ULs, 297 individuals exceeded the manufacturer-recommended dose. Of these, 172/297 (58%) surpassed the UL by at least one nutrient.
Conclusions:
middle-aged, part-time or full-time jobs, using tablet-form DS, and using DS for 6 months or more were associated with DS consumption exceeding the manufacturer-recommended dose, which may lead to excessive nutrient intake.
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