Selenium, cautions
Is 200 mcg/d selenium too much over the long-term?
What to do when high selenium levels won’t come down, even if you’ve stopped supplementing.
Accidental death from acute selenium poisoning.
High selenium impairs hepatic insulin sensitivity through opposite regulation of ROS
If you have over 3 mg you have toxicity. It causes hair and nail loss or brittleness.
With concentrations of 3 ppm or higher in plants, livestock become afflicted with a variety of symptoms: Chronic poisoning may be manifested in the form of emaciation, loss of hair, deformed growth in hoof and horn. In acute cases, animals may suffer from difficulties in moving or from blindness. Selenium competes with sulfur in the body, interfering with the sulfhydryl enzymes. This causes degenerative changes to occur in most internal organs of the body. Plants which are very high in selenium content give off a smell approximating garlic or rotten eggs, which makes recognition easy. Plants growing in acid soil may contain selenium which isn't bioavailable.
Selenium deficiency may result from treatment with corticosteroids, proton pump inhibitors and H2 blockers.
Vitamin C: High doses of selenium may decrease absorption
Adverse Reactions
Case Report: Oral consumption of 10 g of sodium selenite supplement for treatment of prostate cancer resulted in the death of a 75-year-old man .
Chronic selenosis(doses greater than 1000 mcg/day): Muscle weakness, fatigue, peripheral neuropathy, dermatitis, nail and hair changes/loss, garlic breath/body odor, irritability, growth retardation, hepatic necrosis.
Toxicity: Acute toxicity via selenium poisoning has been reported with either accidental or suicidal ingestion of gun bluing solution or sheep drench. Consumption of gram quantities of selenium can cause severe gastrointestinal and neurological disturbances, acute respiratory distress syndrome, myocardial infarction, and renal failure.