Abstract
Use of dietary supplements in the U.S. has increased steadily over the last 25 years. While misformulation is uncommon, the consequences can be serious. A March 2008 voluntary market recall removed supplement products responsible for the most serious selenium toxicity outbreak that has occurred in the U.S. We quantified selenium concentrations in the misformulated supplement products, measured the temporal response in the nail biologic monitor, and associated exposure to self-reported selenosis symptoms. Subjects recruited through state health departments and referrals provided samples of the misformulated supplement products, exposure information, monthly toenail and or fingernail clippings or onycholysitic nail fragments, and listed their newly onset adverse health effects attributed to selenium toxicity. Ninety-seven subjects enrolled and submitted at least one test sample. Peak selenium concentrations (up to 18.3 and 44.1 μg/g for toenails and fingernails, respectively) were measured. Multiple samples (52 total) of all six recalled supplement lots were analyzed ranging from 22,300 to 32,200 μg selenium per daily dose. Average consumption was 30.9 ± 13.9 doses; 73 subjects provided follow-up data on selenosis symptoms at 2.50 ± 0.14 years. Nail samples accurately reflect exposure in this selenium toxicity outbreak, which resulted in long-term/permanent adverse health effects.
Highlights
Selenium (Se) is a required trace-element micronutrient having a recommended dietary allowance (RDA) of 55 to 70 micrograms per day [1]
Results including Se concentrations in Total Body Formula‖ (TBF) supplement products, extent of Se overexposure from these products, the temporal response in the TN and FN biologic monitors, and selenosis symptoms experienced and their persistence are reported
The modest overage (17%) we found in the 234 μg/dose product is similar to what we have measured in other dietary supplements containing Se [17]; the 356% overage measured in the 911 μg/dose product substantially exceeds anything we have measured previously but is itself dwarfed by the 6 misformulated TBF lots produced in September
Summary
Selenium (Se) is a required trace-element micronutrient having a recommended dietary allowance (RDA) of 55 to 70 micrograms (μg) per day [1]. Saturation of the serum selenoprotein P concentration, which occurs at a higher Se intake, has been proposed as a better estimate of the Se requirement [2]. There are at least 25 mammalian selenoproteins [3] having biological functions or expressions known to various degrees [4,5]. Se in 1957 [6], the recognition of selenocysteine (Sec) as the 21st amino acid and the mechanism by which Sec is inserted in mammalian proteins [7,8], and the implication of selenoproteins in the etiologies of cancer, and cardiovascular disease [9,10,11], have generated substantial interest in the scientific community that has been translated through the popular press to the general public, often promoting an increased Se intake through supplementation. Studies of higher than normal Se intakes in a seleniferous area in the U.S [12] and Enshi County of Hubei Province of China [13] led to the establishment of the Tolerable Upper Limit (UL), No Observed Adverse Effect Level (NOAEL)
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