Vitamin A-containing dietary supplements from German and US online pharmacies: market and risk assessment.

Vitamin A supplements are used by many people, and the number of newly registered dietary supplements is continuously increasing. The preparations fall under food law and are not subject to the strict controls of pharmaceuticals. Risk indications and maximum quantity recommendations, e.g., from the Bundesinstitut für Risikobewertung (BfR) and the U.S. Food and Drug Administration (FDA) are not binding, which means that overdoses and potentially serious health problems can easily occur. The hepatotoxicity and teratogenicity of vitamin A are well documented, and other negative effects of high doses of vitamin A are also being discussed. Nevertheless, preparations with exorbitantly high doses are freely available for sale and unrestricted. In this study, 75 supplements containing vitamin A available in Germany and 26 available in the USA were critically examined on the basis of various parameters such as the recommended daily dose according to the manufacturer, daily therapy costs (DTC), the presence of warnings about overdose, use during pregnancy and breastfeeding, and information on adverse effects/interactions. The aim was to gain insights into their risk potential and to examine the need for closer monitoring and stricter guidelines for these preparations. The results show some considerable country-specific differences. Overall, there are serious deficiencies in compliance with the labeling requirements for both the German and the US preparations, and the dosages are often far too high in view of the applicable expert recommendations. Overall, these deficits can pose a risk for consumers that is difficult to assess in its entirety, especially for vulnerable consumer groups. It should be noted that the US preparations perform better overall than the German preparations. This suggests better regulation of dietary supplements in the US market. Based on the available data and literature research, it is doubtful whether the intake of vitamin A-containing preparations, without a diagnosed vitamin A deficiency, has a positive health benefit. Furthermore, it should be examined whether vitamin A should continue to be offered over-the-counter as a food supplement.