Key Factors Driving Portuguese Individuals to Use Food Supplements—Findings from a Cross-Sectional Study

Data on food supplement (FS) consumption profiles are scarce. This study aims to characterise FS consumption among Portuguese adults and identify personal, social, professional, and health-related factors influencing FS use. A cross-sectional study was conducted using an online questionnaire between July and September 2023. The participants were categorised into healthcare professionals (supplement users and non-users, i.e., HPS and HPnS) and non-healthcare professionals (supplement users and non-users, i.e., nHPS and nHPnS). Group distributions were compared using the χ2 test. FS use is very prevalent in Portugal. Significant differences emerged between HPs and nHPs regarding factors associated with FS use. Socioeconomic and professional characteristics, nutritional knowledge, and healthy lifestyles (e.g., eating habits) were all linked to FS consumption. Despite the differences between the groups, across groups, higher education levels, higher nutritional knowledge, and healthier lifestyle habits, such as engaging in sports and healthy food habits, translate into a higher consumption of FSs. The frequent use of FSs in Portuguese adults is associated with higher education, nutritional knowledge, and healthy lifestyles. HPs have specific attitudes through FS use. These findings indicate the need for further research to explore the various types of FSs being utilised and the underlying motivations behind their usage. HPs’ access to FS scientific information and providing practical guidance to promote responsible and informed FS use within the population is crucial.