Selenium Toxicity in Dietary Supplements

ATLANTAInvestigators from the National Center for Environmental Health and the Center for Disease Control (CDC) stated, Toxic concentrations of selenium in a liquid dietary supplement resulted in a widespread outbreak. Had the manufacturers been held to standards used in the pharmaceutical industry, it may have been prevented in an investigation published in the Archives of Internal Medicine (2010;170(3):256-61). Selenium, which is an element necessary for normal cellular function, can potentially have toxic effects at high doses, so an investigation of an outbreak of acute selenium poisoning was conducted. Investigators defined a case as the onset of symptoms of selenium toxicity in a person within two weeks after ingesting a dietary supplement manufactured by "Company A," purchased after Jan. 1, 2008. They conducted case finding, administered initial and 90-day follow-up questionnaires to affected persons, and obtained laboratory data where available.

The source of the outbreak was identified as a liquid dietary supplement containing 200 times the labeled concentration of selenium. Of 201 cases identified in 10 states, one person was hospitalized. The median estimated dose of selenium consumed was 41,749 µg/d (recommended dietary allowance is 55 µg/d). Frequently reported symptoms included diarrhea (78 percent), fatigue (75 percent), hair loss (72 percent), joint pain (70 percent), nail discoloration or brittleness (61 percent) and nausea (58 percent). Symptoms persisting 90 days or longer included fingernail discoloration and loss (52 percent), fatigue (35 percent) and hair loss (29 percent). The mean initial serum selenium concentration of eight patients was 751 µg/L. The mean initial urine selenium concentration of 7 patients was 166 µg/24 hours.