Zinc is a mineral classified as an essential trace element, meaning that very small amounts are necessary for bodily functioning. Zinc acts as a catalyst for a number of enzymes, helps synthesize proteins and DNA in cells, and boosts the immune system. Zinc is one of 16 essential minerals that must be obtained from dietary sources or supplements because your body can't manufacture them.
Both vitamins and minerals are essential to support life, but unlike proteins, carbohydrates and fats, they don't supply energy. Instead, they are used for a number of essential physiological processes. Vitamins are organic compounds, meaning that they contain carbon, found in all living things and different types of atoms. Minerals are inorganic elements containing just one type of atom. Mineral have a simpler chemical structure than vitamins.
Zinc, like many minerals, is found in a number of foods. Red meat and poultry are the largest sources of zinc for most Americans, according to the Office of Dietary Supplements, although oysters contain more zinc than any other food source. Legumes, nuts, certain seafood such as crab, whole grains and fortified cereals also serve as good sources of zinc. Phytates in plant sources of zinc bind it and decrease its availability, so plant sources don't supply as much zinc as meat. Supplements containing zinc are also available and often sold as over-the-counter cold medications.
The recommended dietary allowance, or RDA of zinc for men age 19 and over is 11 mg per day; women over 19 should consume 8 mg per day. The 1988 through 1991 National Health and Nutrition Examination Survey, called NHANES III, found that between 35 and 45 percent of adults over age 60 consumed less than the RDA of 9.4 mg for elderly men and 6.8 mg for elderly women, the ODS reports. Other groups at risk for zinc deficiency include vegetarians and people with gastrointestinal disorders that affect absorption. Because alcohol decreases zinc absorption and increases urinary excretion, between 30 and 50 percent of alcoholics have zinc deficiencies, according to the ODS.
Zinc nasal sprays used to treat cold symptoms can cause loss of smell, medically called ansomia. The USDA has advised consumers not to use nasal sprays containing zinc. Taking more than 100 mg per day of zinc for a 10-year period doubles the risk of developing prostate cancer in men, MedlinePlus warns. Typical side effects of zinc include stomach symptoms such as nausea, vomiting, stomach cramps, loss of appetite and headache.