The use of dietary supplements (DSs) has been steadily increasing all over the world and additionally, the sales of DSs have dynamical increased in the wake of coronavirus disease 2019 (COVID-19) in most of the countries. We investigated DSs phenomenon in 2020 through (1) exploration of Google searches worldwide and in Poland (with Google Trends (GT) tool), and (2) analyses of results of PLifeCOVID-19 Online Studies conducted during the first and second wave of the pandemic. The conducted GT analysis and cross-sectional studies revealed that during the COVID-19 outbreak in March 2020, the interest in immune-related compounds and foods like vitamins C and D, zinc, omega-3, garlic, ginger, or turmeric, as well as their consumption increased. Improving immunity was the main reason behind the supplementation and changes in consumption of pro-healthy foods. GT analysis has shown these interests were positively correlated with the interest in COVID-19, but adversely with cumulative cases or deaths. Respondents tended to start supplementation during the first COVID-19 wave rather than the second one. Except for the role of vitamins D and C, zinc, and selenium in patients with deficiencies of those nutrients, there are no clear and convincing studies that support the role of DSs use in COVID-19 prevention and treatment in healthy, well-nourished individuals. Moreover, as the risk of elevated intake of some nutrients due to the popularity of DSs exists, effective education of consumers in rationale use of DSs and health-protecting behaviors against COVID-19 should be developed.
Keywords: COVID-19; Google Trends; bioactive compounds; dietary supplements; fatty acids; immunity; internet; nutrients; vitamin C; vitamin D; zinc.