HE-141
TRACE MINERALS
Prepared by Jean M. Howe, Extension Specialist, and Natalie N. Hardison, Extension Associate, Foods and Nutrition

Nutrition affects the health of every individual throughout the life cycle. People need nutrients for optimal growth, functional performance, and continued well-being.
More than 40 nutrients are considered essential to human health—essential in the sense that they must be obtained, preformed from food, because the body does not produce enough of these nutrients on its own.
The minerals present in the body are commonly divided into two general groups. One group consists of the macrominerals—calcium, phosphorus, magnesium, sodium, potassium, and chloride. These minerals are present in the body in larger amounts and are required in diets in amounts ranging from hundreds of milligrams to grams. The other group consists of the trace minerals or trace elements such as iron, manganese, copper, iodine, zinc, fluoride, selenium, molybdenum, chromium, and others. The trace minerals are present in the body in exceedingly small amounts.
During the last two decades remarkable advances have taken place in research on trace minerals. Much has been learned about interactions between minerals and other dietary factors; much remains to be learned. As a group, trace minerals are unique in several ways.
1.	Several known mineral deficiency illnesses are due to geography. For example, simple goiter was prevalent where the soil and water are low in iodine. The use of iodized salt has done much to reduce the incidence of simple goiter and cretinism.
2.	Trace minerals are essential to good health, but we need them in only very tiny amounts. The daily requirements of trace elements is not measured in grams or milligrams but usually in micrograms or millionths of a gram. (It takes 1,000 micrograms to equal 1 milligram and 1,000 milligrams to equal 1 gram. A gram is about 1/28 of an ounce.)
However, many trace elements which enter the human body are incompletely utilized. The factors that influence the utilization of each mineral include the chemical form of mineral, amount of mineral in diet, amount of competing mineral in diet, other food components, and the body’s need for the mineral. All these factors interact in a complex manner. Therefore, the total diet and the nutritional status of the individual are both important because they affect the utilization of trace minerals in the body. The 
degree to which man can utilize a nutrient present in a food or supplement is often referred to as bioavailability.
3.	Any nutrient is beneficial to the body only within a specific range of intake. Lack of adequate amounts of a nutrient impairs health, but overconsumption of a nutrient also can harm health. This concept is very important, especially with trace minerals, because the toxic levels for many trace elements may be only several times usual intakes.
Also, many trace elements interact in such a way that the requirement level, as well as the deficient and toxic levels, of trace elements depend in part on intakes of other trace elements. Excessive intakes of single elements can result in a mineral imbalance and, eventually, in a toxicity or deficiency of one or more trace minerals.
4.	Even though most trace minerals are widely distributed in foods, no one food alone furnishes balanced amounts of trace elements. One-sided dietary habits can promote trace mineral deficiency or imbalance especially when calorie intake is low. On the other hand, self-prescribed use of trace mineral supplements to increase intakes of certain minerals can be dangerous. The consumption of a balanced diet which includes a wide variety of foods is the best assurance of safe and adequate intakes of all essential trace minerals, vitamins, and micronutrients (not yet identified as essential).
The most comprehensive guidelines for nutrient intake are provided by the Food and Nutrition Board of the National Academy of Sciences/National Research Council. The board periodically updates its recommended dietary allowances (RDA’s) for various age and sex groups. An RDA for a nutrient is an intake considered adequate to meet the needs of practically all healthy persons in a given population.
Trace minerals with established RDA’s are iron, zinc, and iodine. Ranges of daily intakes which the board described as “estimated safe and adequate intakes” were published in 1980 for six others: copper, manganese, fluoride, chrominum, selenium, and molybdenum.
Following is a discussion of each of these trace minerals mentioned above. Some inorganic elements present in food for which there is no acceptable evidence of essential need in the diet of animals or human are not included in this publication.
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA