Zinc is essential for the normal development and function of many immune cells [79].

Because of the critical role it plays in the immune system, even a mild deficiency can impair immune function and increase the risk of bacterial, viral, and parasitic infection [80].

In clinical states associated with immunodeficiency, zinc can restore natural killer cell activity, lymphocyte production, and resistance to infections [81, 82, 83, 84].

Zinc deficiency is associated with hormonal imbalances that can lead to ovarian function problems, menstruation irregularities, and infertility [149].

Several studies have found that zinc administration was able to reduce the severity and duration of menstrual pain in women [160, 161, 162].

One study reported that an intake of antioxidants (i.e., vitamin C, vitamin E, selenium, and zinc) was inversely correlated with the severity of endometriosis progression in women, indicating that zinc may slow the development of this disorder [164].

In 134 disabled hypothyroid patients under anticonvulsant therapy (with zinc deficiency), zinc was able to normalize thyroid hormone levels and restore thyroid function [235].

A study on 25 children with Down’s syndrome suggested similar effects.

It was also able to reverse the damaging effects of computer monitor-emitted radiation on the thyroid hormone levels [236].

Seminal zinc concentration was positively correlated with sperm count, motility, and viability in different clinical trials [197, 198, 199].

This is likely because of zinc’s role in stabilizing the cellular membranes and DNA (by reducing oxidative damage) of sperm cells and enhancing spermatogenesis (formation of new sperm cells) [200, 201, 202].

In infertile men (with low blood testosterone), supplemental zinc led to an increase in sperm count, testosterone, dihydrotestosterone (DHT), and fertility [203].

Zinc is highly concentrated in the prostate and testes and is involved in the synthesis of testosterone [205, 206].

In 60 patients with non-alcoholic liver cirrhosis, zinc improved liver function and prevented excessive copper accumulation, which can damage the liver [165].

It was able to improve liver function, based on alkaline phosphatase and bilirubin levels, in 30 patients with alcoholic liver cirrhosis [166].

Zinc improved the outcome of 62 patients with hepatitis C which, if left untreated, can lead to liver scarring [171, 172].