In T.E. Tuormaa, "The Adverse Effects of Zinc Deficiency", J.Orthomolecular Med. 10(3&4):149-164, 1995 we learn that:

Zinc is a vital part of all the major metabolic pathways. This almost ubiquitous "cofactor" is involved in the activity of more than 200 enzymes, as for instance superoxide dismutase and DNA and RNA polymerase.

Zinc is essential for immune function, for fertility, gestation and growth, for neural and brain functions (deficiencies can lead to conditions as grave as psychosis and as common as memory loss). It is also an essential factor in optimal nutrition, optimal wound healing, and the health of skin and hair.

It is particularly necessary in all cases of anorexia, bulimia, immunodeficiency, alcoholism, mental depression, infertility and pregnancy.