¶ … dehydration impacts on human metabolism. In this sense, a short introduction in the issue of deficient water input is followed by delimitating the notions of metabolism and dehydration in terms of definition and classification. Afterwards, focus falls on the possible degrees of dehydration and body mass loss, and their implications for a human body. According to Susan Kleiner, Ph.D., "water is the one essential element to life as we know it" (Rabkin, 2000). It makes up approximately 60% of an individual's body mass. Each human cell, tissue and organ needs it in specific amounts in order to function properly, and nearly every life-sustaining body process requires it, too. Water is present in human muscles, fat cells, blood and even bones, transporting nutrients and oxygen to cells, helping to discard waste products, moistening skin tissues, mouth, eyes and nose, and most importantly, keeping body temperature in check.

Thus, water is unspeakably essential and the most important nutrient in a human body, comprising up to 70% of muscles and 75% of the brain. The only thing that surpasses water in level of necessity is, oxygen, and yet, with each exhalation, humans lose water, adding up to as much as two cups per day. Moreover, water evaporates unknowingly through the skin surface, making for the loss of an additional two cups per day. In addition, people lose through urination as much as 2 and half pints over the course of 24 hours. During an average day, one healthy adult can basically lose 8 to 10 cups of water (Reilly, 1998).

More than one-third of all Americans are chronically dehydrated. This condition is reached as the body loses 1 to 2% of its weight in fluid, and it can have serious effects on every aspect of bodily function, from memory, to kidney function, to heart rate. In fact, even a mild case of dehydration is a cause for concern, because it leads to fatigue, lethargy, anxiety, and affects muscle and brain function. In serious cases, the body's blood flow decreases, and dehydration pressures the heart into pumping harder in order to keep the blood flowing, which increases the risk for the occurrence of a heart attack.

Main body

Metabolism is the physiological process comprised from a sum of chemical reactions which occur within every cell of a living human body and are designed to provide energy for vital processes and for synthesizing new organic material. As a matter of fact, the energy obtained from metabolic nutrients is funneled into various growth and other maintenance processes.

According to one classification, there are 2 types of dehydration, namely water loss dehydration, or hyperosmolar, occuring due to either increased sodium or glucose, and salt and water loss dehydration, or hyponatremia (Thomas et al., 2008). Dehydration pertaining to a water deficit is either hypernatremic or hyponatremic when it occurs along with hyperglycemia, and dehydration caused by a salt and water deficit is hyponatremic, or, more rarely, isotonic. Nevertheless, in most cases, dehydration connected with disease or the effects of medication, and it is not primarily due to insufficient water intake.

According to a second classification, there are four types of dehydration (Allen & Prentice, 2005). The first type is mild hypovolemia, whereby the fluid intake is insufficient to meet the body's needs, and 2-5% body weight loss occurs, along with a spectrum of yellow urine, dry lips, and reduced skin elasticity. Secondly, hypertonic or hypernatremic dehydration occurs as body water losses surpass sodium losses, enhancing blood osmolality and thus causing hypernatremia. This type of dehydration may be accompanied by fever, intense sweating, and/or evaporative water loss. Thirdly, isotonic dehydration means that the human body loses equal amounts of water and sodium, by other venues than perspiration. In this case, blood electrolytes are normal, but there is gastrointestinal fluid loss, namely vomiting, diarrhea, accompanied by acute weight loss, tachycardia, and orthostatic hypotension. Finally, hypotonic dehydration or dilutional hyponatremia develops anytime the body sodium loss exceeds water loss, or when isotonic dehydration is treated only with water.

Water mediates various enzymatic and chemical reactions in the human body, transporting nutrients, hormones, antibodies and oxygen through the blood stream and lymphatic system. Water is the principal solvent of the body and it regulates all functions, including the activity of each element it dissolves and circulates. Also, the proteins and enzymes that are part of the organism function more efficiently in a low viscosity environment.

When water losses are not replenished, a physiological chain reaction occurs. Receiving the message of water insufficiency, hormones give the signal...

Together with contributing to constipation and bloating, dehydration increasingly affects other body systems as well. For instance, 1% dehydration leads to thirst, whereas 2% dehydration produces feelings of anxiety, reduced appetite, and a 20% decrease in work capacity. 4% dehydration causes feelings of nausea, together with dizziness, emotional instability and fatigue.
Next, 6% dehydration leads to loss of coordination and incoherence in speech. A quota of 10% dehydration causes thermoregulation failure, in addition to all above mentioned symptoms, and cell necrosis starts to appear. At a level of 11% dehydration, drinking water does not suffice because the chemical balance of the organism has undergone serious changes, and thus professional medical care is required in order to restore the initial conditions. Lastly, a 20% dehydration state may lead to death (The effects of dehydration, online).

What is more, at 3% body weight loss, muscular endurance diminishes, at 4% dizziness occurs, and physical labor capacity declines by as much as 30%. At 5%, problems related to concentration appear, along with drowsiness, impatience and headache. 6% body weight loss due to dehydration means that the heart is racing, and the body's temperature regulation system starts to fail, and athletes may even notice that they've stopped sweating. At a level of 7%, there's a fair chance of collapse (Reilly, 1998)

It would be interesting to note that thirst is a poor indicator of fluid requirements or of the precise degree of dehydration. In general, the sensation of feeling thirsty is not perceived until a person has lost at least 2% of body mass. As the body becomes more and more dehydrated, a reduction in blood flow and sweat rate may occur. A high humidity level may limit evaporative sweat loss, which will lead to further rises in core temperature, resulting in fatigue and possible heat injury to body tissues, which could turn out to be fatal (Lanham-New et al., 2011).

Dehydration impacts on a wide range of cardiovascular and thermoregulatory responses, culminating with an increase in core temperature amounting to 0.10-0.40°C for every 1% decrease in body weight as water (Consequences of dehydration, online). Regarding the impairment in cardiovascular and thermoregulatory responses due to dehydration, a possible explanation might be the reduction in skin blood flow and sweating rate, which inevitably leads to a rise in core temperature.

Interestingly, exercise or heat-induced hypohydration increases the osmotic pressure of the plasma. Eccrine sweat is usually hypotonic in relation to plasma, hence the plasma turns hyperosmotic when hypohydration is induced by exercise and sweat secretion. And hypohydration combined with hyperthermia in a moderate environment reduces maximal aerobic power by 6% and exercise time by 12% from euhydration levels (Consequences of dehydration, online).

When dehydration steps in, pains that vary in topography and intensity appear as a desperate request of the body for water, and because of the acid burns inside the cells. Depending on the location of these centers of high acid content, pain may occur in certain areas of the human body. These pains are simply the evidence that acid accumulations need to be purged with large amounts of liquid, and they include heartburn, dyspepsia, angina, colitis, as well as rheumatoid, lumbar, fibro-myalgic pains and migraines.

The regular state of the intracellular fluid is a weakly alkaline environment, and the water that circulates around the body enters the cells and carries out molecules of hydrogen, which determine the level of acidity. The body needs to be adequately hydrated so that it will be able to maintain the normal hydrogen ion concentration, or normal pH, equal to 7.4. In dehydration the acid accumulates inside the cells causing burns that provoke intense pain, yet if the body is adequately hydrated, it keeps the weakly alkaline environment.

The first sign that the acid concentration in the body is becoming critical is heartburn pain, whereby the mucus membrane of the stomach tells that the organism is in dire need of water. Actually, this type of pain appears at the first signs of dehydration and may mislead not only a patient but also a doctor who might misinterpret this symptom as an indication for diagnostic surgery. Sometimes, the pain localizes around the appendix and looks like appendicitis, and in other cases it moves to the intestine and looks like colitis. Nonetheless, all these symptoms are alarms of dehydration and signals of thirst that our body sends out.

Strange as it may seem, bulimia is another manifestation of the sense of thirst that…