Chapter 139 Water
The Most Basic Nutrient and Therapeutic Agent
Pure water has been undervalued as a therapeutic tool because of a number of false assumptions and beliefs, according to Dr. Fereydoon Batmanghelidj. Conceptual fallacies in regard to the body’s need for and use of water are as follows:
Water is the predominant compound in the human body. At birth, a baby’s body is 78% water by weight. The average young adult is 70% water, and although the body’s water content declines with age, water content remains at no less than 50% even in the geriatric individual. During youth, most cells with the exception of adipose cells are 90% water. In adulthood, two-thirds of body water resides within cells; the remainder resides in the extracellular spaces.2 Even bone tissue is 22% water.
• Building material. Water molecules facilitate the folding of amino acid chains assembled on the basis of DNA genetic sequences and reinforce the structural integrity of proteins. Water molecules fill every space not occupied by other molecules in every nook and cranny of every cell.
• Solvent. The ionic nature of water molecules makes water an excellent solvent of ionic compounds: salts, glucose, amino acids, etc.4 The tendency of water molecules to surround ions and molecules of solutes allows chemical agents to move freely to wherever they are needed.
• Reaction medium and reactant. The biochemical reactions that sustain life occur within the medium of water. Yet water is not just the medium in the background; it is also an active participant—a reactant in the hydrolysis of macromolecules such as proteins, carbohydrates, and fats. Water is also a by-product of the metabolism of food energy molecules that contain hydrogen: carbohydrates, proteins, and fats.
• Carrier for nutrients and waste products. Water is the transport medium that moves nutrients into cells and waste products out of cells and then out of the body. Water is also the most basic constituent of blood, indispensable to the function of the cardiovascular, respiratory, urinary, and nervous systems.5
• Thermoregulation. The electromagnetic bonds among water molecules give water a great capacity to absorb heat, hold heat, and resist temperature changes. This property allows water to support homeostasis by helping to maintain body temperature. In addition, the evaporation of water from the skin as perspiration releases heat sufficiently to maintain body temperature even when the surrounding atmospheric temperature is higher than body temperature.
• Lubricant. Water combines with molecules forming viscous substances that lubricate and protect tissue functions. Examples include the mucus of the respiratory and gastrointestinal mucous membranes, synovial fluid in joints, saliva, tears, etc.
• Shock absorber. Within the cell, water takes the structural configuration of a gel that maintains cellular shape and form. This property cushions tissues against the shock of movement and mild trauma. Water molecules have an affinity for the electronegative molecules of connective tissue matrix (e.g., chondroitin, keratin, etc.), including the nucleus pulposus of the vertebral discs. It is the water molecules surrounding the compounds of the connective tissue matrix that provide the cushioning effect.
The osmoreceptors in the hypothalamus are sensitive to only certain solutes in the blood (e.g., sodium) but insensitive to others (e.g., urea).6 Thus, the osmoreceptors are not accurate gauges of blood solute concentration and water need at the cell level. The “thirst center” of the hypothalamus, triggered by osmosreceptor reaction to solute concentration, is distinct from the osmoreceptors.
Unfortunately for optimal hydration, the sense of thirst in the mouth (dryness) is quickly and easily satiated by small amounts of water, stimulating the moisture receptors within the mucous membranes of the mouth, throat, and upper gastrointestinal tract. Although thirst returns if the osmoreceptors and thirst center are not satiated, the body is caught in a game of catch-up that it can never win because it is never allowed to be in a continuous state of optimal hydration.
Perspiration is hypotonic; that is, it has lower electrolyte content than plasma or extracellular fluid. This phenomenon means that sweating leads to more water loss than electrolyte loss. As the electrolyte concentration in the extracellular fluid rises, it draws water out of cells (intracellular fluid), leading to cellular dehydration. This state of hypertonic dehydration demands replenishment with hypotonic beverages, such as pure water. Water need supersedes salt need during endurance exercise.8
The National Athletic Trainers’ Association has published guidelines for athletic hydration. Here are some highlights of their recommendations that apply equally to “weekend warriors” and those involved in heavy physical labor10:
• Ensure that athletic activity begins in a well-hydrated state. Pre-exercise hydration entails consuming 500 to 600 mL (17 to 20 fl oz) of water 2 to 3 hours before exercise and 200 to 300 mL (7 to 10 fl oz) of water 10 to 20 minutes before exercise.
• Replace fluids sufficiently to meet sweat and urine losses and maintain hydration by preventing at less than 2% body weight reduction. This need requires 200 to 300 mL (7 to 10 fl oz) every 10 to 20 minutes.
• Hydrate postexercise to correct any fluid loss, ideally within 2 hours after exercise. When rehydration must be rapid, compensate for urine losses during rehydration by drinking 25% to 50% more than sweat losses to assure optimal rehydration 4 to 6 hours after exercise.