Trace Elements // Zinc
Zinc plays important roles in growth and development, the immune response, neurological function, and reproduction. On the cellular level, the function of zinc can be catalytic, structural, and regulatory (2).
Zinc plays an important role in the structure of proteins (e.g., antioxidant enzyme) and cell membranes (4, 5). Loss of zinc from biological membranes increases their susceptibility to oxidative damage and impairs their function (5).
Zinc-stabilized proteins have been found to regulate gene expression by acting as ‘transcription factors’, binding to DNA and influencing the expression of specific genes.
Additionally, zinc has been found to play a role in programmed cell death (‘apoptosis’), regulating cellular growth and development, as well as a number of chronic diseases (7).
Supplemental but not dietary levels of iron (38–65 mg/day) may decrease zinc absorption (8) ― a point of concern in the management of iron supplementation during pregnancy and breast-feeding (‘lactation’) (9, 10).
Zinc is a component of a vitamin A (retinol)-binding protein, necessary for transporting vitamin A in the blood. Zinc is also required for the enzyme that converts retinol to retinal, which is necessary for the synthesis of a protein in the eye (‘rhodopsin’) that absorbs light and thus is involved in dark adaptation. Zinc deficiency is associated with decreased release of vitamin A from the liver, which may contribute to symptoms of night blindness that are seen with zinc deficiency (13, 14).
The European Food Safety Authority (EFSA), which provides scientific advice to assist policy makers, has confirmed that clear health benefits have been established for the dietary intake of zinc in contributing to:
- a normal function of the immune system;
- normal DNA synthesis and cell division;
- the protection of cell constituents from oxidative damage;
- the maintenance of normal bone;
- normal cognitive function;
- normal fertility and reproduction;
- normal metabolism of fatty acids;
- normal acid-base metabolism;
- normal metabolism of vitamin A;
- the maintenance of normal vision;
- normal protein synthesis;
- the maintenance of normal serum testosterone concentrations;
- normal carbohydrate metabolism;
- normal macronutrient metabolism;
- the maintenance of normal skin;
- the maintenance of normal hair;
- the maintenance of normal nails.