Trace minerals are a key part of a well-balanced diet, which is the best assurance of proper nutrition, according to a registered dietitian at New York University Medical Center.

Minerals are inorganic substances that are part of all cells and play a key role in metabolism, the process of the body that transforms food and then uses it for energy and growth."Some minerals are called trace minerals because the body needs them in very small amounts," said Una Finn.

Among the most important of the trace minerals are iron, iodine, copper, zinc, manganese and fluorine. These elements have been shown to work in conjunction with vitamins to be protective to the body. Deficiencies are sometimes diagnosed by blood tests or urinalysis.

"However, experienced health professionals can sometimes make observations which lead them to discover a nutritional problem," she said. "Obvious changes in the appearance of the hair or the skin pigmentation can be signs."

A deficiency of iron can cause anemia. In 1989, there were nearly 4 million reported cases of chronic anemia, a condition marked by a reduction of red blood cells or hemoglobin, the substance that helps red blood cells to transport oxygen to the body. Heavy menstrual flow can cause iron-deficiency anemia in women of child-bearing age.

"Sources of iron in the diet include: red meat, eggs, fish and green vegetables," Finn said. "There is an increased need for iron during pregnancy when an iron supplement is usually required."

She noted that an inadequate amount of copper is also implicated in some forms of anemia as well as in skeletal defects; manganese, in conjunction with other elements, is important for healthy bones; a deficiency of iodine can impair the functioning of the thyroid gland; and fluoride is an established weapon against tooth decay.