Unit 10
Water and the Minerals

Maintenance of the body’s 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% 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 much smaller concentrations. Like vitamins, water and minerals do not yield energy, but unlike vitamins, they are inorganic in their chemical composition. Minerals are indestructible, even after being burned to ashes; they 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 also discuss, briefly, the functions, deficiency and toxicity symptoms, and major food sources of sodium, potassium, and calcium.

Instead of providing detailed information on each trace mineral, we look at their general characteristics, such as functions, absorption, transport, excretion, and dietary sources; we cover iron in greater detail than other minerals. Finally, we discuss the need (or lack of need) for vitamin and mineral supplements.

Objectives

After completing this unit, you should be able to

1. discuss at least seven roles of water in the body, state an adult’s daily water needs, and list beverages and foods that can help meet water needs.
2. discuss at least four functions of sodium, the body’s daily requirement and upper limit, the effects of inadequacy and excess, and the major dietary sources.
3. discuss at least three roles of potassium, the body’s daily requirement, the effects of inadequacy, and major food sources.
4. describe at least seven roles for calcium, list five factors affecting calcium absorption, describe body systems affected by toxicity, and list dietary sources.
5. describe the two main functions of trace elements; discuss their absorption, transport, excretion, and potential toxicity; and identify the food groups that provide trace minerals.
6. describe the influence of physical activity on osteoporosis risks, and describe at least seven diet-related factors for osteoporosis.
7. describe at least three functions for iron, six factors influencing absorption, the effects of deficiency and toxicity, and sources of heme and non-heme iron.
8. discuss the appropriate use of vitamin and mineral supplements.