 |
|
|
|
|
|
|
|
 |
|
||||||
 |
 |
 |
 |
 |
 |
 |
|
 |
 |
 |
|
||||
Zinc
Zinc is necessary for proper growth and is involved in more than one hundred enzymes that are essential for digestion and metabolism. It is required for good vision, the replication of DNA, the breakdown and use of carbohydrates, the healing of wounds, and the synthesis of protein. And it plays an important role in the health of the gastro-intestinal tract, the retina of the eye, the immune system, the taste buds, and the production of sperm and the male sex hormone testosterone.
The amount of zinc absorbed by the body is affected by its interaction with other minerals and by the presence of phytates in a meal. Phytates or phytic acid are found in many (but not all) of the same foods as dietary fibre, and they combine with zinc to make it unavailable for absorption. Foods high in phytates include bran, soybeans, barley, oats, corn, peanuts, wheat, peas, and potatoes. As a result vegetarians often find it difficult to get enough zinc.
Zinc is lost from the body each day in sweat, urine and faeces; and an inadequate dietary intake over an extended period of time can produce a state of chronic deficiency. Those most at risk are alcoholics, athletes, vegetarians, sufferers of kidney or pancreatic disease, people with sickle-cell anaemia, and pregnant or lactating women. Alcohol increases the amount of zinc excreted in the urine, and in pregnant alcoholics it impairs the transport of zinc across the placenta to the fetus. Fetal alcohol syndrome is in part linked to the depletion of zinc in the fetal tissue. Athletes (especially endurance runners) are at risk because of the amount they sweat and because many of the high-carbohydrate foods they consume are low in zinc.
Zinc deficiency can be particularly dangerous during pregnancy. It can cause prolonged gestation and labour, and create risks to the fetus during the third trimester. Zinc deficient mothers experience a higher incidence of deformed or stillborn babies. As a result, women who are pregnant or lactating should see their physicians about a supplement. Signs of Zinc deficiency include slow healing of woundss, loss of taste and appetite, impaired mental ability, hair loss, poor night vision, tremors, increased susceptibility to infection, and pustular rashes on the limbs, mouth and genital area. In children it can cause retarded growth and delayed sexual developement. In adults it can cause a reduction in testosterone and sperm production, inability to maintain a constant body weight, and a higher than normal level of ammonia in the blood (a toxic by-product of the breakdown of protein).
Zinc is not very toxic, unless taken in extremely high doses (more than 15 times the RDI (US: RDA). However, large doses may cause vomiting and diarrhoea, and if taken for extended periods of time, may impair the ability of the white blood cells to fight infection, cause an increase in LDL ("bad cholesterol"), a decrease in HDL ("good cholesterol"), and interfere with the absorption of copper and iron; and in pregnant women - premature labour and stillbirth. Good sources of zinc include liver, oysters, lean meat, crabmeat, chicken (especially dark meat), cheese, yogurt, nuts, eggs, bacon, turkey, and pumpkin seeds.
Content & Updated by Reps Mags (MNU)