Factors associated with dietary supplement use among physically active adults in Saudi Arabia: an analytical extension of a population-based study.

Background: Dietary supplement (DS) use is common among physically active individuals, but evidence on factors associated with DS use and related behaviors in Saudi Arabia remains limited. This study represents the second stage of a two-part investigation among physically active adults in the Eastern Province of Saudi Arabia. Part I described the prevalence and general patterns of DS use, whereas Part II examined factors associated with DS use, supplementation frequency, self-reported adverse effects, and nutritional fact-label reading. Methods: A cross-sectional study was conducted among 755 physically active adults (379 males and 376 females) recruited by quota sampling. Part II was a secondary analysis of the same dataset and the same participants included in Part I. Data were collected from November 2023 to January 2024. Participants were Saudi nationals aged 18-60 years who had engaged in physical activity for at least 12 consecutive weeks, provided informed consent, and completed the questionnaire. A validated online questionnaire assessed sociodemographic characteristics, physical activity, DS use and practices, self-reported adverse effects, purchase sources, perceived metabolic enhancement (categorized according to the self-reported percentage of improvement), and nutritional fact-label reading. DS use referred to consumption of at least one dietary supplement during the previous year. A four-category multinomial outcome represented sex-specific DS-use status, with female non-users as the reference category. Multinomial and binary logistic regression models were used to identify factors associated with DS use, supplementation frequency, adverse effects, and label-reading behavior. Results: Overall, 505 participants (66.9%) reported using at least one DS during the previous year. Although DS use was similarly prevalent among men and women, associated factors differed by sex. Among women, DS use was associated with fitness-, strength-, and cardio-oriented activities, whereas among men it was associated with training frequency and employment status. Supplementation frequency was associated with training frequency, age, sex, and post-exercise recovery. Self-reported adverse effects were associated with younger age and internet purchasing, while nutritional fact-label reading was associated with female sex, public-sector employment, and greater perceived metabolic enhancement. Conclusions: DS use is common among physically active individuals in Saudi Arabia and is associated with sex-specific, behavioral, and sociodemographic characteristics. These findings emphasize the multifaceted nature of supplementation practices and support targeted, evidence-based strategies to promote informed and safe DS use.