A predisposition for the efficiency of nutraceuticals is that the product contains a sufficient quantity of a vitamin. Several studies have highlighted different quality issues. Our objective was to investigate whether the contents of the vitamins in selected types of food supplements were in accordance with labeling. We focused on two types of food supplements where content-related quality issues could result in public health risks: food supplements for supplementation with (a) folic acid (as 5-methyltetrahydrofolate (5-MTHF)) in pregnancy and (b) with vitamin D in the general population. The study was done on supplements from the global supply that are typically used by Slovenian consumers. We sampled one production batch of 30 different food supplements-six and 24 samples with 5-MTHF and cholecalciferol, respectively. We found samples with vitamin contents outside the 80-150% tolerance interval in both sets. Particularly, 5-MTHF was found to be more problematic, probably due to its lower stability. This study shows the need for better quality control. Quality control is needed during both the manufacturing process and product shelf lifetimes. Content quality should be also subject to external controls by authorities. Voluntarily quality control schemes would also enable consumers to identify products of sufficient quality.
Keywords: cholecalciferol; dietary supplements; folate; folic acid; food supplements; public health; quality; safety; vitamin D.