Physiological function of zinc
Zinc has an important role in growth and development, immune function, substance metabolism and reproductive function.
(1) A component of metalloenzymes or an activator of enzymes. There are about 200 kinds of zinc-containing enzymes in the body, among which the main zinc-containing enzymes are superoxide dismutase, malate dehydrogenase, alkaline phosphatase, lactate dehydrogenase, etc. These enzymes play an important role in participating in tissue respiration, energy metabolism, and antioxidant process. Zinc is an essential trace element for maintaining the activity of RNA polymerase, DNA polymerase and reverse transcriptase.
(2) Promote growth and development and tissue regeneration. Zinc is involved in protein synthesis and cell growth, division and differentiation processes, and growth and development have a close relationship. Zinc can be directly involved in the regulation of gene expression, thus affecting growth and development. Zinc also promotes the normal development of sex organs and sexual functions.
(3) Promote immune function. Zinc is necessary to ensure the integrity of the immune system. Zinc deficiency can cause thymic atrophy, reduced thymic hormones, impaired T-cell function and altered cell-mediated immune function.
(4) Maintaining cell membrane structure and function. Zinc can interact with various groups and receptors on the cell membrane to enhance membrane stability and resistance to oxygen free radicals.
In addition, zinc and salivary protein synthesis of gustatory elements can enhance appetite, lack of zinc can affect the sense of taste and appetite, and even the occurrence of xenophagia. Zinc has a protective effect on the skin and eyesight, zinc deficiency can cause skin roughness and epithelial keratinization.
Zinc absorption and metabolism
Zinc is absorbed by the small intestine, with an absorption rate of 20% to 30%. Zinc is absorbed 15 minutes after ingestion and begins to concentrate in the liver, then distributed to other tissues. zinc concentration in plasma reaches its peak after 4 hours. Most of the plasma zinc is bound to albumin and ? -macroglobulin, and is distributed to the organs and tissues as the blood enters the portal circulation.
Zinc forms a complex with albumin that is readily absorbed by the tissues. The body's absorption of zinc is related to the concentration of zinc in the intestinal lumen, and the rate of absorption increases when the body is deficient in zinc.
Many factors can affect the absorption of dietary zinc. Vegetable food tannins, phytic acid and cellulose are not conducive to the absorption of zinc; iron inhibits the absorption of zinc; alcoholism can hinder the absorption of zinc. Animal zinc bioavailability is higher; some drugs such as iodoquinolines, phenytoinna and vitamin D can promote the absorption of zinc.
Zinc is mainly excreted from the intestinal tract, the kidneys and skin can also excrete a certain amount. In the summer heat and sweating or pathological sweating, zinc is lost in large quantities, and zinc deficiency in the body may occur.