Local studies have documented the contributions of minerals to the health status of mammals. Selenium (Se) is an example of such minerals. It is essential for the activation and functioning of enzymes. In Nigeria, the mineral has been reported to be present in water, foods and soils. While the soil selenium concentrations determine selenium levels in foods, difference in food concentrations of the mineral atones for the variations in the plasma and tissue selenium level across the geopolitical zones of Nigeria. Areas in Nigeria prone to erosion could be associated with inadequate soil selenium levels and this might lead to low availability of the mineral in the foods consumed by animals and humans. The plasma selenium levels in Nigerians may vary from as low as 0.006 mg/L to as high as 0.3279+/-0.0546 mg/L depending on the geographical factors and analytical methods employed. Studies in which the physiological effects of selenium supplementations were investigated revealed an improvement in CD4 counts in HIV positive human subjects, reduction in rats’ susceptibility to trypanosomiasis, improvement in reproductive function, acceleration of ulcer healing in animal model of experimental gastric ulcer and mitigation of the adverse effects in animal model of gastric ulcer. Low plasma selenium levels are associated with HIV infection, fertility problems, postpartum cardiomyopathy and diabetes mellitus. Therefore, there is growing need for dietary selenium supplementations in Nigeria.