COVID-19 is still the biggest issue worldwide. Many dietary supplements on the market claim to have anti-COVID-19 effects without scientific evidence. To elucidate the prevalence of dietary supplement usage for the prevention of COVID-19, we conducted an online cross-sectional questionnaire survey among Japanese adults in January 2022. The prevalence of dietary supplement use for the prevention of COVID-19 was 8.3%, and there was no gender difference. We also conducted additional research on these dietary supplement users (1000 males and 1000 females). The most popular ingredient used was vitamin C (61.0%), with vitamin D (34.9%) and probiotics (33.4%) following. Half of these participants reported using supplements for more than one year. The information sources that reportedly led them to start using dietary supplements for the prevention of COVID-19 were the Internet (44.0%), television and radio (29.9%), and family or friends (26.0%), and these information sources differed among generations. In conclusion, some of the population used vitamin/mineral supplements for the prevention of COVID-19 that might be beneficial for their health, but some used ingredients with no scientifically proven effects against the virus at this time. Therefore, information-based scientific evidence is important to prevent the inappropriate use of dietary supplements by consumers.
