Vitamin B12, also known as cobalamin, is an essential water-soluble vitamin belonging to the B-complex vitamins. Long-term vitamin B12 deficiency is associated with the development of hematological, neuropsychiatric, and gastrointestinal disorders. Since vitamin B12 naturally occurs primarily in foods of animal origin, the risk of deficiency is higher among individuals following vegetarian or vegan diets. Therefore, adequate vitamin B12 supplementation is important for the prevention of vitamin B12 deficiency, with food supplements being increasingly used for this purpose. These products are becoming progressively widespread on the Slovenian market, however, compared to medicinal products, they are far less regulated. To assess the quality of food supplements containing cobalamins, we evaluated the presence and content of the four forms of vitamin B12 currently authorized for use in food supplements (adenosylcobalamin, cyanocobalamin, methylcobalamin, and hydroxocobalamin). For this purpose, a previously developed high-performance liquid chromatography method was used, which we appropriately validated. A set of 31 food supplements containing one or more vitamin B12 forms, including products of different dosage forms, manufacturers, and price ranges was tested in the study. Initially, we assessed the actual presence of the declared cobalamins in the supplements and found irregularities in 19 out of the 31 analyzed products. The most frequently detected irregularity was the presence of hydroxocobalamin, which had not been declared on the product labeling. Since hydroxocobalamin is a degradation product of other cobalamin forms, its formation is most probably the result of their instability. We also evaluated the content of the declared cobalamin forms and compared the results with the values stated on the labels. In accordance with the European Commission guidelines, the acceptable content range was defined as 80–150 % of the declared value. Among the 31 analyzed food supplements, 17 contained appropriate amounts of vitamin B12, whereas 13 products contained insufficient levels and one product contained an excessively high level. The analysis of food supplements included an evaluation of the impact of dosage form and manufacturer on product quality, as well as an assessment of the relationship between price and quality. Comparison of products in different dosage forms showed that tablets were of the highest quality, while liquid formulations showed the lowest quality. Higher product price was not necessarily associated with better quality but was primarily related to higher labelled cobalamin content. Overall, the results indicate that the quality of cobalamin-containing food supplements on the market often fails to meet the expected quality standards, highlighting the need for more stringent quality control.
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