How Safe are Antioxidant Food Supplements Containing Selenium?

Three antioxidant food supplements were analysed for selenium (Se) and its species. Sample A main constituents were coenzyme Q10, selenium (as medical yeast), vitamin C and natural vitamin E. The product is used for maintaining health and strengthening physical and mental abilities, stimulating the immune system, inhibiting the development of atherosclerosis, strengthening a weakened heart. Sample B main constituents were coenzyme Q10, selenium, vitamin E and beta-carotene. The product is advertised as high dosage natural coenzyme Q10, which provides supply of energy to all cells of human body. Sample C main ingredients were coenzyme Q10, selenium (as sodium selenite), beta-carotene and vitamin E with the same positive effects described as for the samples A and B. The samples were digested and analysed for Se content by hydride generation atomic fluorescence spectrometry (HG-AFS). For Se speciation, enzymatic hydrolysis with the enzyme protease was performed and soluble Se species was determined by ion-exchange chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The results showed that the value of Se obtained for one of the products (C) far exceeded the declared value; instead of 10 µg Se per capsule, 69 µg of Se per capsule was found. The declared Se species in the same product was sodium selenite, but only SeCys2 was detected (55% of the total Se). In product B that did not have a declared Se form added, we detected 60% of total Se as selenite. In product A 75% of total Se was present as SeMet. It is worrying that the Se species determined and declared were different in two selected antioxidant food supplements.