Unit 10
Water and the Major Minerals

Often neglected as an essential nutrient, water is in fact 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 per cent, and death from loss of 20 per cent. The reason is that water is involved in many biochemical reactions, and serves as an important solvent and medium for vital materials.

Maintenance of the fluid and electrolyte balance 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 per cent 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 next unit.

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 water balance is maintained. We discuss the importance of electrolytes in regulating the distribution, composition, and acidity of body fluids. We provide an overview of the functions, deficiency, and toxicity, and major food sources of sodium, potassium, and calcium, and we also discuss, briefly, the use of calcium supplements.

This unit consists of the three sections listed below.

• Section 10.1  Water and Electrolytes
• Section 10.2  Sodium and Potassium
• Section 10.3  Calcium