Trace elements are inorganic substances required by living things in minute quantities. There are 24 natural elements that are essential to life. The major elements, carbon, oxygen, hydrogen and nitrogen comprise 96% of the weight of living matter. In addition, the major mineral elements, macrominerals, make up another 3.7%. These include calcium (1.5), phosphorus (1.0), potassium (0.4), sulfur (0.3), sodium (0.2), chlorine (0.2) and magnesium (0.1). Trace elements, microminerals, make up the final 0.3% of the body's weight. The trace elements are iron, iodine, copper, zinc, manganese, cobalt, chromium, selenium, molybdenum, fluorine, tin, silicon, and vanadium. Although required in small amounts, organisms need these substances for their well-being. Some of the trace elements are needed by all forms of life, whereas only particular species need others. For example, all forms of life need iron because it is a component of cytochromes that function in cellular respiration. Vertebrates, on the other hand, require iodine to synthesize thyroid hormones.
Nutritionists recommend that humans have macrominerals in amounts more than 100 mg per day, and microminerals in amounts less than 20 mg per day. The normal daily intake of iodine, for example, is only 0.5 mg. Both animal and plant products serve as food sources for trace elements. Minerals exist in small amounts in the soil, but plants are able to take them in and concentrate them. Animals depend on eating plants to obtain many of their trace elements. Microminerals have specific functions in the body.
Vertebrates use iron, not only in cytochromes, but also to produce hemoglobin, the pigment in red blood cells that carries oxygen. Too little iron in the diet causes iron-deficiency anemia and impairs the immune system. Whole grains, legumes, meats, eggs, and green leafy vegetables are iron-containing foods. An iodine deficiency causes, goiter, an enlargement of the thyroid. Zinc, found in meat, seafood, and grains, is a component of certain proteins and digestive enzymes of the body. Lack of zinc results in poor growth and development. Fluorine, found in drinking water and seafood, maintains tooth structure and prevents decay. Manganese, found in nuts, grains, and vegetables, acts as an enzyme cofactor and is required to build normal bone and cartilage.
Scientists have discovered various microelements over a period of years, and continue to do so. Molybdenum, selenium, chromium, vanadium, and silicon are the most recently discovered on the list. Of these, molybdenum serves as an enzyme cofactor, prevents excretory disorders, and is found in grains and legumes. Selenium, found in meat, seafood, and grains, is an antioxidant that works with vitamin E. Chromium, found in yeast and meat, aids in the breakdown of glucose for energy. Nutritionists believe that a well-balanced diet is the best way to get micronutrients. Nevertheless, many people take vitamin and mineral supplements. There is a danger, however, in taking micronutrients in large quantities. In one study, researchers gave high doses of zinc to participants, only to find that many of the subjects suffered from non-fatal heart attacks. In other studies, they found that a high dose of one mineral can block the body's absorption of another.
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