Here is the answer :
Zinc deficiency usually results from inadequate intake of foods high in zinc, such as seafood, oatmeal, bran, meat, eggs, and nuts, or from impaired absorption caused by short bowel syndrome, Crohn's disease, or pancreatic insufficiency. It may also be due to
excessive intake of foods containing iron, calcium, vitamin D, and the fiber and phytates in cereals , that bind zinc to form insoluble chelates that prevent its absorption. It occasionally can results from blood loss caused by parasitism. Alcohol, cirrhosis, dialysis, burns, draining wounds, and corticosteroids increase renal excretion of zinc.
Moreover synthetic zinc compounds, which are often excreted soon after they are consumed, and zinc oxide and zinc sulfate, which must combine with specific organic compounds before the zinc becomes available
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