Water and Hydration



Chapter 1

Water and hydration

Introduction

Water is the only one nutrient which is essential to human existence (Williams, 1988), and the largest single constituent of human body Voke et al. (1998).It makes up from 40 to70 of an individual's body mass, depending on age, sex, and body composition, it constitutes 65 to 75 of weight of muscle and about 5% of the body mass McArdle et al. (2007) .However the most abundant constituent of every tissue ( Adolph et al 1933) although, observe that the water plays a key role in maintaining multiple physiological functions (Tomas et al 2008).Every cell contains fluid of the exact composition Roifese et al. (2006).Approximately 42L of total body water (TBW) is intracellular (ICW) with an 28L and14L extracellular water (ECW)( Gropper et al, 2009).

Water is stared in several body compartments but mores constantly between compartments, about 60 to 65 percent of body water is stored inside body cell as intracellular water Williams (2009),This total collective water inside the cells amounts to about twice that out side the cells(Williams 1988), and about 35 to 40 percent is out side the cells and is termed extracellular water (Williams 2009), the extracellular fluid is collective water through out the body out side the cells makes up a bout 20% of total body weight (Williams 1988), Approximately 25 percent of the extracellular component is in the vascular system and 75% outside the body vessels. The total body volume is about 8% of body weight. (Ganong, 2003).

Water intake:

In normal life the intake of fluid is largely determined by social custom and habit (Passmore et la, 1986).The water intake comprises the fluid drunk (Passmore et al 1986) and water in food that are eaten (Williams 1988). The water formed as a product of cell oxidation when nutrients are burned in the body for energy (Williams 1988), while water losses occur from renal , through the skin, as water vaporing expired air (McArdle et al 2009),and gastrointestinal tract losses (Dietary reference intake 2004). Water is normally enter by moth via liquid and food, this mixture is digested and absorbed within the gastrointestinal tract, therefore, water intake can be estimated from measured fluid volumes and food intake. Water losses can be estimated from a variety of physiological and biophysical measurements and calculations. (Adolph, 1933; Williams, 1988; Passmore, 1986).Depending on environment exposure, age, activity level, functional losses and metabolic needs (Williams, 1988).Metabolic water production is formed by oxidation of hydrogen containing substrate during metabolism or energy-yielding nutrients (Dietary reference intake 2004).Maughan et al( 2007), observed that, for an individual eating a mixed diet (60% carbohydrates, 30% fat and 10% protein) and maintaining energy and macronutrient balance on an intake of about 3000 kcal per day, water of oxidation will amount to a bout 400 ml per day. However oxidation of 1 g of carbohydrate, protein, and fat yields 0.6, 0, 41, and 1, 07 g of metabolic water, respectively (Williams, 1988).

Body water and age

The relationship between age and body water I contrast to ...