Unit 10
Water and the Major Minerals

Often overlooked as an essential nutrient, water is the most indispensable and abundant component of living cells. A person can survive without food for several weeks, but can live without water for no more than a few days. Severe malfunctions can result from loss of body fluids of 10%, and death from loss of 20%. The reason is that water is involved in many biochemical reactions and serves as an important solvent and medium for vital materials.

Maintenance of fluid and electrolyte balance in the body requires proper amounts of sodium, chloride, and potassium, which—along with calcium, phosphorus, sulphur, and magnesium—constitute the major minerals present in the body. The major minerals in humans are defined as those making up 0.01% or more of body weight. One one-hundredth of a per cent is not a large amount, yet many minerals—called trace minerals—are present in the body in much smaller concentrations; they are discussed in the Unit 11.

Like vitamins, water and minerals do not yield energy; unlike vitamins, they are inorganic in their chemical composition. Minerals are indestructible, even after being burned to ashes. Minerals are lost in cooking only when leached out into the cooking water.

In this unit, we look at the functions of water in the body and at how the body maintains water balance. We discuss the importance of electrolytes in regulating the distribution, composition, and acidity of body fluids. We provide an overview of the functions of water; deficiency and toxicity symptoms; and major food sources of sodium, potassium, and calcium. We also discuss, briefly, the use of calcium supplements.

This unit consists of three sections:

10.1—Water and Electrolytes
10.2—Sodium and Potassium
10.3—Calcium

Objectives

After completing this unit, you should be able to

1. identify the functions of water in the body.
2. describe the causes of fluid and electrolyte imbalance, and describe how acid-base balance is maintained.
3. discuss the following about sodium and potassium:
   1. Identify their functions in the body.
   2. Describe the symptoms of deficiency and excess intake.
   3. Discuss their relationship to blood pressure.
   4. List some of their major food sources.
   5. Discuss dietary strategies to reduce salt and sodium intake.
4. discuss the following about calcium:
   1. Identify its functions in the body.
   2. Describe the hormonal regulation of its blood level.
   3. Discuss the physiological and dietary factors that influence its balance.
   4. Discuss deficiency symptoms.
   5. List some of its major food sources.
   6. Discuss some of the factors to consider when using supplements.
5. list the risk factors for osteoporosis and discuss preventive measures.