RESUMEN
Background The purchase of dietary supplements (DS) via the Internet is increasing worldwide as well as in the Czech Republic. Objective The aim of the study is to evaluate the quality of information on DS available on the Internet. Setting Czech websites related to dietary supplements. Methods A cross-sectional study was carried out involving the analysis of information placed on the websites related to the 100 top-selling DS in the Czech Republic in 2014, according to IMS Health data. Main outcome measure The following criteria were evaluated: contact for the manufacturer, recommended dosage, information on active substances as well as overall composition, permitted health claims, % of the daily reference intake value (DRIV) for vitamins and minerals, link for online counseling, pregnancy/breastfeeding, allergy information, contraindications, adverse reactions, and supplement-drug interactions (some criteria were evaluated from both points of view). Results A total of 199 web domains and 850 websites were evaluated. From the regulatory point of view, all the criteria were fulfilled by 11.3% of websites. Almost 9% of the websites reported information referring to the treatment, cure, or prevention of a disease. From the clinical point of view, all the criteria were only met by one website. Conclusions The quality of information related to DS available on the Internet in the Czech Republic is quite low. The consumers should consult a specialist when using DS purchased online.