Zinc is an essential trace element of all highly proliferating cells in the human body. It is essential to the development and growth of all organisms. Zinc plays a critical role in modulating resistance to infectious agents and reduces the duration, severity, and risk of diarrheal disease via improved regeneration of intestinal epithelium, improved absorption of water and electrolytes, increased levels of brush border enzymes, and, possibly, an enhancement in the immune response allowing better clearance of pathogens. On the cellular level, zinc finger motifs play various roles including diverse functions that involve specific gene expression for ion channels throughout the body. It maintains the function and the structure of the membrane barrier by contributing to host defense, which is particularly crucial in the intestines due to the continuous exposure to noxious agents and pathogens. Zinc deficiency is characterized by impaired immune function, loss of appetite, and growth retardation. More severe cases cause diarrhea, delayed sexual maturation, hair loss, eye and skin lesions, impotence and hypogonadism in males, as well as weight loss, taste abnormalities, delayed healing of wounds, and mental lethargy. The objective of this study is a critical review of the molecular and genetic regulation of zinc in various cellular processes and organs, the association between zinc and diarrheal disease, the recommended dietary zinc intake, and the effects of zinc deficiency on the human body.