Chapter Introduction

14

TRACE MINERALS

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Small Quantities with Big Importance HOW LACK OF TRACE MINERALS CAN WREAK HAVOC ON YOUR HEALTH

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LEARNING OBJECTIVES

  • Describe the major functions of copper, fluoride, iodine, iron, selenium, and zinc in the body (Infographics 14.1 and 14.12)

  • Identify the general properties of trace minerals (Infographic 14.2)

  • Describe how the use of iodine and the production of thyroid hormone are controlled (Infographic 14.3)

  • Describe the symptoms of deficiency and toxicity for copper, fluoride, iodine, iron, selenium, and zinc (Infographics 14.4 and 14.12)

  • Identify at least two dietary sources of copper, iodine, iron, selenium, and zinc (Infographics 14.5 and 14.8, 14.9, 14.10, 14.11, and 14.12)

  • Discuss the dietary sources of heme and non-heme iron and the factors that affect their absorption (Infographics 14.6, 14.7, and 14.8)

GOITER enlargement of the thyroid gland, most often caused by lack of iodine in the diet

In the days that led up to World War I, a great swath of the United States was known as “the goiter belt,” because alarming numbers of men, women, and children in the area were showing signs of goiter, an enlargement of the thyroid gland. During the draft for World War I, the Michigan State Department of Public Health found that the prevalence of goiter reached as high as 64.4% in some parts of Michigan. Many of the military recruits were deemed too unhealthy to serve in the war effort.

The soils of the Great Lakes, Appalachians, and Northwestern regions of the United States are poor in the trace mineral iodine. The body needs iodine, an element that is transported in the body as iodide, to make thyroid hormones, which play key roles in many essential metabolic processes. Most of Earth’s iodine is found in oceans and iodine content in the soil varies by location, which affects the iodine content of crops. In some regions of the world, particularly mountainous areas, or flooded river valleys, iodine-deficient soil is common, increasing the risk of iodine deficiency among people who consume foods primarily from those areas.

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An abnormal enlargement of the thyroid gland is called a goiter. The thyroid is a butterfly-shaped gland located at the base of the neck. It secretes several hormones that affect metabolism, growth, and development.

Since the days of World War I, many countries have implemented programs to add iodine to table salt and have dramatically reduced the prevalence of iodine deficiency worldwide. However, iodine deficiency is still “one of the most important public health issues globally,” according to a 2012 study published by researchers at the Boston Medical Center. In the United States, where much of our table salt is iodized, most people appear to consume sufficient iodine to offset deficiency, although certain groups, such as pregnant women, may be at risk of suboptimal intake and iodine status.

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