Section 12. Disorders of Nutrition and Metabolism

Chapter 155. Minerals and Electrolytes

Topics: Introduction | Calcium | Copper | Fluoride | Iodine | Iron | Magnesium | Phosphate | Potassium | Selenium | Sodium | Zinc

Introduction

Minerals are necessary for the normal functioning of the body's cells. The body needs large quantities of sodium, potassium, calcium, magnesium, chloride, and phosphate. These minerals are called macrominerals. The body needs small quantities of copper, fluoride, iodine, iron, selenium, and zinc. These minerals are called trace minerals.

Minerals are an essential part of a healthy diet. The recommended dietary allowance (RDA)--the amount most healthy people need each day to remain healthy--has been determined for most minerals. People who have a disorder may need more or less than this amount.

Consuming too little or too much of certain minerals can cause a nutritional disorder. People who eat a balanced diet containing a variety of foods are unlikely to develop a nutritional disorder or a major mineral deficiency, except iron or iodine deficiency. However, people who follow restrictive diets may not consume enough of a particular mineral. For example, vegetarians, including those who eat eggs and dairy products, are at risk of iron deficiency. Consuming large amounts (megadoses) of mineral supplements without medical supervision may have harmful (toxic) effects.

Some minerals--especially the macrominerals--are important as electrolytes. The body uses electrolytes to help regulate nerve and muscle function and acid-base balance (see Section 12, Chapter 159). Also, electrolytes help the body maintain normal volume in its different fluid-containing areas (compartments). Electrolytes are dissolved in three main compartments: the fluid within the cells, the fluid in the space surrounding the cells, and the blood.

To function normally, the body must keep the concentration of electrolytes in its compartments within very narrow limits. The body maintains the concentration of electrolytes in each compartment by moving electrolytes into or out of the cells. The kidneys filter the electrolytes in the blood and excrete any excess in the urine to maintain a balance between daily intake and output.

If the balance of electrolytes is disturbed, disorders can develop. An electrolyte imbalance can occur when a person becomes dehydrated; uses certain drugs; has certain heart, kidney, or liver disorders; or is given intravenous fluids or feedings in inappropriate amounts.

To detect nutritional disorders or an electrolyte imbalance, doctors measure the levels of minerals in a sample of blood or urine.

See the table Minerals.