THE IMPORTANCE OF ZINC
Zinc is the 24th most abundant element in the earth's crust at 75 ppm. In seawater, it is found at levels up to 30 ppb. Human tissues and bone contain between 50 and 170 ppm zinc and soils can range from 5 to over 750 ppm.
It is an essential element for animals and plants incorporated in over 200 different enzymes and transcription factors that regulate growth, development, longevity, fertility, digestion, and the immune system. Although zinc is stored in many lifeforms, it is not easily released to make up for a dietary lack. A significant amount is lost daily in waste products and therefore a regular intake is vital. Many diets are more likely to be deficient in zinc than iron. Semen is particularly rich in zinc and has been associated with low sperm counts in men.
In higher organisms zinc in absorbed from foods in the gut. However, it can react with phytic acid, commonly found in many cereals and beans forming zinc phytate, which cannot be absorbed. The need for zinc in the plant kingdom is evident by crops that store and deplete the element from soils subsequently creating future crops deficient in the element. Contrarily, at elevated levels, zinc in soil interferes with absorption of other elements including iron, manganese, and boron.
Higher forms of life that are zinc deficient require 50% more food to gain the same weight as one that is supplied with sufficient zinc. Zinc ion is quite soluble but is easily absorbed by minerals, clays, and organic matter where it is strongly bound.