The Mechanics of Water
The Science of Nutrition
Perhaps you have heard the phrase “water is life”. When it comes to the human body, nothing could be more accurate. The system of fluids in the body that water affects controls everything from nerve impulse to movement; it is even part of the very structure of our bodies. The following will discuss the vital connection between different systems in the body and how they use water to maintain proper health and function. We will discuss what happens to the body when we intake too much water (water toxicity), likewise when we lose or intake too little (dehydration).
Why is water essential to health maintenance? Water is the “great regulator” in the body. It has several functions: to dissolve nutrients and move them throughout the body, to flush and carry waste particles from the body, and to assist in regulating pressure across all systems within the body. So, where is the water in our bodies? It is estimated the over half your body weight is comprised of water. Men actually tend to carry more water as they tend to have higher muscle mass: about 60 to 65% water. Muscle tissue is comprised of about 75% water. Women fall somewhere between 50 and 60% of water weight (Grosvenor, Smolin, 2006). Water is in the cells that make up tissue and organs: even in our bones. The water inside cells is called intracellular fluid and passes through the walls of cells with the assistance of proteins, sodium, and potassium which are dissolved in the body. This ebb and flow of intracellular fluid controls the levels of dissolved substances in the different compartments of the body. When particle concentrations are too high, water flows in to dilute, lowering the concentration to a proper level. When too low, water flows away from the compartment, thus raising the concentration. This process of diffusion is called osmosis. Osmosis is a mechanism in nature by which water in an organism is used to balance dissolved particle concentrations. Osmosis is also responsible for moving water from the lining in the gastrointestinal tract or lumen, into the blood. The water in blood and which flows between cells is called interstitial fluid. Think of this as the vehicle which moves critical nutrients and oxygen to vital organs. It also moves waste material to the lungs and kidneys and serves as a delivery system for all the chemical defense mechanism in the body such as antibodies which fight of infection and cancerous cells.
Just like we see in nature, water has several housekeeping functions. It is used as a flushing agent to cleanse internal and external surfaces and acts as a lubricant for many functions. Consider saliva: water in saliva lubricates food for easier chewing and to assist in swallowing. The eyes tear up to remove dust. And not unlike the Tin Man in the Wizard of Oz, our joints would creak or not move at all if it were not for water-based synovial fluids. Water even protects against shock in certain compartments by cushioning the eyes and joints.
When considering all this water, one would think we would have to be drinking it all day long in order to function. However, the body has internal mechanisms that regulate water levels in the different compartments and lets us know when we need more or less of it. The primary intake of water for the average person comes from drinking water or other fluids like tea and soda pop. Water is also found in solid foods such as fruits, vegetables, and meats. So, if we are taking in all this water, where does it go? We pass water by way of urine and feces and also through evaporation from the lungs and skin via sweat. Have you ever breathed heavily on a mirror to fog it up? That fog is actually water vapor from your lungs. Because water does not store in the body like fat cells, the daily intake and excretion must balance. Otherwise systems in the body begin to have problems.
Initial loss of water in...
References: Grosvenor, Smolin. (2006). Water and Minerals. In L. S. M.B. Grosvenor, Nutrition: Everyday choices. (pp. 282,285,287). Hoboken: John Wiley & Sons.
Mayo Clinic Staff. (2007, January 7). Dehydration. Retrieved July 11, 2011, from The Mayo Clinic: http://www.mayoclinic.com/health/dehydration/DS00561
WebMD. (2010, February 24). Health and Fitness: Dehydration- Prevention. Retrieved July 11, 2011, from WEbMD.com: http://www.webmd.com/fitness-exercise/tc/dehydration-prevention
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