Adverse Health Effects of Selenium in Humans

The document reviewed the adverse health effects of selenium exposure in humans, highlighting that chronic exposure to selenium compounds was linked to several health issues. Early toxic effects included disruptions in endocrine function, particularly affecting thyroid hormone synthesis at dietary exposures of around 300 micrograms Se/d, and impacting the metabolism of growth hormone and insulin-like growth factor-1. Selenium exposure also impaired natural killer cell activity and, at higher levels, caused hepatotoxicity and gastrointestinal disturbances. Dermatological effects such as nail and hair loss and dermatitis were noted after high environmental selenium exposure. Neurotoxicity, including motor neuron degeneration and increased risk of amyotrophic lateral sclerosis, was a concern with chronic exposure to both organic and inorganic selenium compounds. The review suggested that selenium might have a dual effect on cancer risk, either increasing or decreasing it. The study concluded that existing environmental selenium exposure limits were insufficient to prevent adverse health effects.