Selenium Deficiency

An estimated 500 million to 1 billion people worldwide are overtly deficient in selenium. The phosphorus component of conventional NPK fertilizers renders selenium unavailable to plants, preventing its accumulation up the food chain. Many people have subclinical selenium deficiencies that go undetected. Selenium is distributed unevenly across the earth's crust, concentrating in coastal and iodine-rich soils; iodine-poor regions are likely selenium-poor as well.