Role of Zinc in Human Health with Reference to African Elderly: A Review
This review of the literature was conducted to assess dietary zinc intake among the African elderly, discuss the potential impact of current levels of zinc intake on their health, and to recommend strategies for improving their dietary zinc intake. As zinc plays an ubiquitous role in human metabolism, determination of its dietary intake among African elderly is important from a health standpoint, if the consequences of widely reported deficiency are to be mitigated. Animal meats and seafood are rich sources of zinc, with nuts and legumes being relatively good plant sources. Zinc bioavailability is relatively higher in animal foods due to absence of inhibitors of zinc absorption and the presence of cysteine and methionine, which improve its absorption. Zinc in plant-based foods is less bioavailable for human metabolism due to presence of chelators, phytates and dietary fibre, which inhibit absorption. Individuals at the greatest risk of zinc deficiency include infants and children, pregnant and lactating women, patients being fed intravenously, malnourished individuals including those with protein-energy malnutrition and anorexia nervosa; others are individuals with chronic or persistent diarrhoea, malabsorption syndromes, those with alcoholic liver disease, sickle cell anemia, strict vegetarians, and the elderly aged 60 years and over. A reduced capacity to absorb zinc, increases the likelihood of disease states that may adversely alter zinc utilization, and increased use of drugs that increase zinc excretion, may all contribute to increased risk of mild to moderate zinc deficiency in the elderly. Also, in situations of diminished access to adequate and balanced diets, health care and good sanitation, the likelihood of developing mild to moderate zinc deficiency is high among poor African elderly. Due to the consequences of impaired immune system function in zinc deficiency in the elderly, it is critical to maintain an adequate zinc intake by this group. Despite mild zinc deficiency being unlikely to lead to severe zinc deficiency in individuals without a genetic disorder, zinc malabsorption or conditions of increased zinc loss such as severe burns can also result in mild to severe zinc deficiency. Diets for poor African children, pregnant and lactating women, and the elderly, are deficient in zinc. This is mainly due to low food intake, relatively lower intake of animal foods and high phytate and fibre content of the staple plant-based foods. Fortification of staples and inclusion of inexpensive and available animal protein sources, in plant-based diets for the elderly can increase their dietary zinc intake.