Section 12. Disorders of Nutrition and Metabolism

Chapter 155. Minerals and Electrolytes

Topics: Introduction | Calcium | Copper | Fluoride | Iodine | Iron | Magnesium | Phosphate | Potassium | Selenium | Sodium | Zinc

Zinc

Zinc is widely distributed in the body. It is a component of more than 100 enzymes, including those involved in the formation of RNA (ribonucleic acid) and DNA (deoxyribonucleic acid). The level of zinc in the body depends on the amount of zinc consumed in the diet. Zinc is necessary for healthy skin, healing of wounds, and growth. Much of the zinc consumed in the diet is not absorbed.

Zinc Deficiency

Zinc deficiency is most likely to develop in people who eat little meat, liver, eggs, or seafood. Consuming phytic acid (found in grains) and large amounts of iron and calcium may reduce the absorption of zinc. Liver and pancreatic disorders, alcoholism, diabetes mellitus, and disorders that impair absorption can cause zinc deficiency. Taking diuretics can also cause zinc deficiency. People who must be fed intravenously for a long time may develop this deficiency. Acrodermatitis enteropathica, a rare hereditary disorder in which zinc cannot be absorbed, may result in zinc deficiency as well as diarrhea and rashes.

Early symptoms include a loss of appetite and slowed growth in infants and children. Other symptoms include patchy hair loss, impaired taste and smell, inflammation of the skin (dermatitis), and night blindness. In men, sperm production may be reduced. The body's immune system and ability to heal wounds may be impaired. In acrodermatitis enteropathica, symptoms usually appear when an affected infant is weaned.

Doctors suspect zinc deficiency on the basis of the person's circumstances, symptoms, and response to zinc supplements.

Zinc Excess

Consumption of excess zinc is rare. It usually results from consuming acidic foods or beverages packaged in a zinc-coated (galvanized) container. Symptoms include a metallic taste in the mouth, nausea, vomiting, and diarrhea. Consumption of 1 gram or more (about 70 times the RDA) may be fatal. In certain industries, inhaling zinc oxide fumes can cause rapid breathing, sweating, and weakness--a disorder called metal fume fever. Consuming too much zinc for a long time can reduce the absorption of copper and impair the immune system.

Doctors suspect the diagnosis based on the person's circumstances and symptoms. Treatment involves reducing zinc consumption.