Clinical Trials of Vitamin Supplements: Are They Meeting the European Medicines Agency Prompt Dissemination Regulation?

Vitamin supplements are over-the-counter medications consumed by the majority of adults. Given that many supplements may be ineffective and/or associated with adverse events, compliance of the registered trials to the European Medicines Agency (EMA) rule for prompt reporting of the results is of crucial importance for consumers’ health. The present retrospective study was designed to evaluate compliance with the European Union (EU) requirement to post the trial results to the EU Clinical Trials Database (EudraCT) and assess the trial characteristics associated with this compliance. Three independent researchers searched the EudraCT for completed trials on vitamin supplements performed on humans. A total of 144 completed trials involving 40,464 participants fulfilled the inclusion criteria. For 45.7% of these, results were due. Trials funded by the industry had approximately quadruple chances of being published, adjusting for their design, masking, comparator, and participant age group. Moreover, trials testing vitamin supplement safety are more likely to report their findings as compared to vitamin efficacy. Many vitamin supplementation trials registered in the EudraCT failed to report their results and adhere to the EMA regulations. Stricter regulations should be imposed concerning trial results reporting to increase transparency and public trust.