Zinc is an essential trace mineral occurring in the body jj in larger amounts than any other trace element except iron. The human body contains approximately 1,81 grams of zinc compared to nearly 5 grams of iron.
Zinc has a variety of functions. It is related toll the normal absorption and action of vitamins, especially the B complex. It is a constituent of at least 25 enzymes involved in digestion and metabolism, including carbonic anhydrase, which is necessary for tissue respiration. Zinc is a component of insulin, and g it is part of the enzyme that is needed to break down alcohol. It also plays a part in carbohydrate digestion I and phosphorus metabolism. In addition, it is essential in the synthesis of nucleic acid, which controls the formation of different proteins in the cell. Zinc is essential for general growth and proper development of the reproductive organs and for normal functioning of the prostate gland.
Recent medical findings indicate that zinc is important in healing wounds and burns. It may also be required in the synthesis of DNA, which is the master substance of life, carrying all inherited traits and directing the activity of each cell.
Soil exhaustion and the processing of food adversely affect the zinc value of the food we eat. The best sources of all trace elements in proper balance are natural unprocessed foods. Diets high in protein, whole-grain products, brewer's yeast, wheat bran, wheat germ, and pumpkin seeds are usually high in zinc.
Zinc is readily absorbed in the upper small intestine. Uptake is only as much as the body needs at the time; the rest is unabsorbed.
The major route of excretion is through the gastrointestinal tract; little is lost in the urine. The largest storage of zinc occurs in the liver, pancreas, kidney, bones, and voluntary muscles. Zinc is also stored in parts of the eyes, prostate gland and spermatozoa, skin, hair, fingernails, and toenails as well as being present in the white blood cells.
A high intake of calcium and phytic acid, found in certain grains, may prevent absorption of zinc. If the intake of calcium and phytic acid is higher, zinc consumption should be increased.
The National Research Council recommends a daily dietary intake of 15 milligrams of zinc for adults. An additional 15 milligrams is recommended during pregnancy, and an additional 25 milligrams is recommended during lactation. The average "good" diet may yield only 8 to 11 milligrams of zinc per day.
Older patients have been given 660 milligrams of zinc sulfate per day with minimal side effects. Some experienced diarrhea. Nausea and vomiting are also symptoms of zinc overdose, requiring a reduction in the amount taken.
High intakes of zinc interfere with copper utilization, causing incomplete iron metabolism. Excessive intake of zinc may result in a loss of iron and copper
from the liver. When zinc is added to the diet, vitamin A is also needed in larger amounts.
Deficiency Effects and Symptoms
The most common cause of zinc deficiency is an unbalanced diet, although other factors may also be responsible. For example, the consumption of alcohol may precipitate a deficiency by flushing stored zinc out of the liver and into the urine. Zinc deficiency is also a factor in stress, fatigue, susceptibility to infection, injury, and decreased alertness.
Zinc deficiency can cause retarded growth, delayed sexual maturity, and prolonged healing of wounds. A deficiency of zinc, copper, and vanadium may result in atherosclerosis. Stretch marks in the skin and white spots in the fingernails may be signs of a zinc deficiency. Brittle nails and hair and hair lacking pigment, irregular menstrual cycles in teen women, impotence in young males, and painful knee and hip joints in teenagers are also indications of a deficiency.
Chronic zinc depletion can predispose body cells to cancer.
Cadmium, a toxic mineral, also plays an important role in zinc deficiencies. High intakes of cadmium will accentuate the signs of a zinc deficiency, and the cadmium will be stored in the body in the absence of zinc. This creates a detrimental situation that can be reversed by increasing the consumption of zinc.
Chelating compounds used to remove excess copper from the body also leach out zinc, which then must be replaced.
Recent studies demonstrate conclusively that zinc deficiency causes sterility and dwarfism in humans. The deficiency leads to unhealthy changes in the size and structure of the prostate gland, which contains more zinc than any other part of the human anatomy. In prostate problems, particularly prostate cancer, the levels of zinc in the prostate gland decline.
James A. Halstead and J. Cecil Smith, Jr., of the Trace Element Research Laboratory, Washington, D.C., have made interesting studies on zinc. They found low zinc levels in the blood plasma of people suffering from alcoholic cirrhosis, other types of liver disease, ulcers, heart attacks, mongolism, and cystic fibrosis. Pregnant woman and women taking oral contraceptives also had low levels of zinc in their blood plasma.
Nausea associated with pregnancy may be a result of too-low levels of zinc and vitamin B6. Zinc-deficient pregnant rats had many stillborn or birth-defective babies; also many offspring were mentally retarded or slow learners.
Excessive zinc excretion occurs in leukemia and Hodgkin's disease, but the causes of this are unknown. A zinc deficiency is characterized by abnormal fatigue and may cause a loss of normal taste senitivity, poor appetite, and suboptimal growth. The zinc-deficient patient has poor circulation and a tendency to faint; therefore care must be taken in anesthetic and operative situations. These people can be prone to shock, excessive bleeding, and delayed wound healing.
Beneficial Effect on Ailments
Zinc helps eliminate cholesterol deposits and has been successfully used in the treatment of atherosclerosis. Zinc may contribute to the rapid healing of internal wounds or any injury to the arteries. Zinc supplements given in therapeutic doses will speed up the rate at which the body heals certain external wounds and injuries.
Zinc is beneficial in the prevention and treatment of infertility. It also helps in the proper growth and maturity of the sex organs, in resistance to infection, improved night vision, and reduced body odor.
The administration of zinc may benefit patients suffering from Hodgkin's disease and leukemia. It also is used in treatment of cirrhosis of the liver and alcoholism.
Zinc is beneficial to the diabetic because of its regulatory effect on insulin in the blood. It has been found that the addition of zinc to insulin prolongs its effect on blood sugar. A diabetic pancreas contains only about half as much zinc as does a healthy one.