Zinc absorption from infant formulas

Zinc and infant nutrition

Zinc is essential for a wide variety of cellular processes in all cells. It is a critical dietary nutrient, particularly in the early stages of life. In the early neonatal period, adequate sources of zinc can be obtained from breast milk. In rare circumstances, the mammary gland produces zinc deficient milk that is potentially lethal for exclusively breast-fed infants. This can be overcome by zinc supplementation to the infant. Alterations to key zinc transporters provide insights into the mechanisms of cellular zinc homeostasis. The bioavailability of zinc in food depends on the presence of constituents that may complex zinc. In many countries, zinc deficiency is a major health issue due to poor nourishment. Young children are particularly affected. Zinc deficiency can impair immune function and contributes to the global burden of infectious diseases including diarrhoea, pneumonia and malaria. Furthermore, zinc deficiency may extend its influence across generations by inducing epigenetic effects that alter the expression of genes. This review discusses the significance of adequate zinc nutrition in infants, factors that influence zinc nutrition, the consequences of zinc deficiency, including its contribution to the global burden of disease, and addresses some of the knowledge gaps in zinc biology.

The functional effects of nutrients on enterocyte proliferation and intestinal ion transport in early infancy

Nutrition has a key role in the modulation of the developing intestine in early infancy, and nutrients are able to modulate several intestinal functions including nutrient absorption, ion transport, cell growth and differentiation, motility and immunomodulation. Such modulation is exerted in part through a direct interaction between a single nutrient and the enterocyte. Two functions--ion transport and cell growth--are closely connected and appear to be modulated by nutrients. This is supported by the finding that a single nutrient (e.g. zinc) stimulates ion absorption and also promotes enterocyte growth. Interestingly, intracellular signalling for either effect is similar and involves mitogen-activated protein kinase. Other nutrients also modulate enterocyte function and there is evidence that their effect may depend on their side of action (apical or basolateral) and concentration. Knowledge of the interaction between nutrients and enterocytes may be exploited to obtain clinical effects using nutrition as a long-term treatment for intestinal and non-intestinal conditions.