Ochratoxin A in brewer's yeast used as food supplement

Brewer's yeasts are rich in vitamins of the B-group and contain other nutritive factors; therefore, they are recommended as valuable food supplements for people with special dietary requirements like pregnant women, children, and adolescents, or for people with high physical activity. Additionally, certain strains of brewer's yeast are known to be capable of adsorbing xenobiotics such as mycotoxins. Because of that, these yeasts are regarded as having positive effects in food, beverage, and feed technology. Their potential to bind mycotoxins such as ochratoxin A (OTA), however, can subsequently lead to a contamination of such brewer's yeasts used as food supplements. In the present study, we analyzed 46 samples of brewer's yeasts for the occurrence of OTA by HPLC with fluorescence detector (HPLC-FLD) and for confirmatory measurements by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Nearly 90% of the samples were contaminated with OTA, the levels ranging from the limit of detection (LOD, 0.01 μg/kg) to 4.2 μg/kg. The mean and median levels of contamination were 0.49 and 0.27 μg/kg, respectively. Based on these results, the additional weekly OTA exposure by regularly consuming such supplements was assessed. Depending on different subpopulations (adults, children) and levels of contamination used for calculation, the additional OTA intake via brewer's yeast products ranged from 9.3% (mean case) to 114% (worst case) of the published mean weekly OTA intake in Germany (adults 279.3 ng, children 195.3 ng). At present, maximum levels for OTA in nutritional supplements like brewer's yeast do not exist. Based on our results, however, it is recommended that producers of these dietary supplements should include mycotoxin analyses in ongoing and future self-monitoring programs and in product quality checks.