Zinc is the 24th most abundant element in the earth's crust and has five stable isotopes. The most common zinc-based mineral is sphalerite (zinc blende - zinc sulphide). Zinc is naturally widespread in inorganic and organic form. The science of compounds that contain carbon-zinc bonds, and which describe their physical properties, synthesis and chemical reactions, is called the chemistry of organozinc reactants / compounds.
.Zinc is a trace element necessary for man and for many other animals, but also for plants and various microorganisms. It represents the second most abundant "metal trace" in man after iron and is the only metal that appears in all classes of biological catalysts but not only. In fact, it is also necessary for the proper functioning of many hormones, including insulin, growth hormone and sex hormones. The body contains a lot of them in muscles, red blood cells and in the white ones; however, large concentrations of zinc can be found mainly in organs. It is essential for the functioning of over 300 enzymes and 1000 transcription factors. It is stored and transferred in metallothioneins (MT) - a family of proteins rich in cysteine, with low molecular weight, mainly located in the Golgi apparatus, capable of binding physiological and xenobiotic metals. There are therefore many biological catalysts of human cells that present centrally a zinc atom, for example alcohol dehydrogenase - the enzyme necessary to metabolise ethyl alcohol.
Zinc is also very important for the development of the embryo and fetus, and for the postnatal growth of the newborn and the child. It has an antioxidant function which, although indirectly, is very important in counteracting oxidative stress.
is 12 mg / day. For children up to 12 months it is 3 mg / day; up to 13 years it is 8 mg / day.Regarding the safety of zinc, the IOM has declared a "Tolerable upper intake levels" (ULs) for adults of 40 mg / day - for children it is lower. Note: UL, such as EAR and RDAs are "Dietary Reference Intakes" (DRIs).
The "European Food Safety Authority" (EFSA - European Food Safety Authority) refers to the "Dietary Reference Values" (DRV - Dietary Reference Values) for "Population Reference Intake" (PRI - reference / recommended intake of the population) , instead of RDA, and the "Average Requirement" (AR - average requirement), instead of EAR.
* PRI: recommended intake for the population, from LARN - Recommended Nutrient Intake Levels for the Italian population
For people aged 18 and over, the PRI calculations are complex, as EFSA has set higher and higher values in relation to the increased content of phytates - chelating antinutrients - in the diet. For women with a "phytate intake increases from 300 to 1200 mg / day, the PRI increases to 7.5 - 12.7 mg / day; for men the range is between 9.4 and 16.3 mg / day. die. Note: These PRIs are higher than the US RDAs. EFSA also set its UL at 25 mg / day, so much less than the US values.
In the labeling of food supplements and dietary foods in the United States, zinc intake is expressed as a percentage of the "Daily Value" (% DV). Still on the labeling, before May 27, 2016, 100% of the daily value was 15 mg, after this date it was revised to 11 mg. Food and supplement companies have until January 1, 2020 to adapt when the parameters are changed.
The main sources of zinc are: fish, red meat, cereals, legumes, nuts and algae. Vegetable zinc is less available because by binding to phytic acid it can form an insoluble complex which is not absorbed.
For more information we recommend reading: Foods rich in zinc.
