The two faces of selenium.

Area of Science:

• Biochemistry
• Nutritional Science
• Toxicology

Background:

• Nutritionally vital trace elements possess high biological activity, influencing enzymes, hormones, and vitamins.
• This biological activity can lead to metabolic disturbances at elevated intake levels, even if still relatively low.
• Selenium exemplifies this duality, with concerns arising from both deficiency and excess.

Purpose of the Study:

• To explore the dichotomous effects of selenium, encompassing its essential nutrient functions and toxicological impacts.
• To investigate selenium's role in preventing deficiency diseases and its potential anticarcinogenic properties.
• To understand the biochemical mechanisms underlying selenium's bioactivity, toxicity, and interactions.

Main Methods:

• Review of historical and contemporary research on selenium's effects in biological systems.
• Analysis of studies investigating selenium deficiency symptoms and essentiality.
• Examination of research on selenium's teratogenic effects and its potential in cancer prevention.

Main Results:

• Selenium is an essential nutrient, with deficiency (below 0.02 ppm) causing muscle, liver, and pancreas issues.
• Glutathione peroxidase identified as a key active form mediating selenium's protective functions.
• Excess selenium demonstrates toxicity, including teratogenic effects in avian fetuses, and shows anticarcinogenic potential in specific contexts.

Conclusions:

• Selenium's biological activity presents a spectrum of effects, from essential nutrient to toxicant.
• Understanding selenium's biochemical roles is crucial for managing both deficiency and toxicity.
• Further research is warranted to identify other active selenium compounds, understand bioactivity interference, and elucidate toxicity mechanisms.