Water: The Only Liquid the Body Needs To live a fully healthy and functional life, water is indispensible. From the point in history when primitive species moved from the oceans to land, a major factor of survival has continually been stopping dehydration. The important adaptations that enable this are present in almost all species of animals, including man. Water makes up varying percentages of the body weight of humans from 75% in infants, to about 55% in the elderly, and is crucial for maintenance of cellular homeostasis (Popkin, D'Anci and Rosenberg). Even though humans can survive a couple of weeks without eating, the human body cannot last even a few days devoid of water (Student Nutrition awareness campaign). Even slight dehydration can disturb physiological functions resulting in headaches, exhaustion, dryness of the mouth, and even muscle weaknesses and mental deterioration, according to Heller (Reinberg).

When talking about body fluids we are basically discussing water. Tight maintenance of the delicate balance existing between the intake and output of water, and its circulation, is essential for optimal performance of all the organ systems in the body. Disruptions to this delicate balance do occur and they must quickly be identified and rectified for the return to normal body fluid homeostasis (Gwinnutt and Thorburn).

Everything that will be covered in this paper concerns pure drinking water which is the perfect beverage without any calories. It is also easily available and is not expensive. Water is the single most important fluid that is required by our bodies because it is the main component of all other fluids in the body.

Other sub-topics covered in this paper include water volume and the constituents in the body, the benefits to the human body, and how dehydration affects the body. A conclusion is also given.

Water

Water makes up about 55-65% of the body weight. It is essential for the optimal function of all body cells. The human blood is made of 83% water while the muscles, brain and bones are made up of 75%, 74% and 10% water, respectively. Water distributes nutrients to the entire body through blood, and it helps eliminate waste via carrying it away from the cells. In the form of sweat, water helps to regulate the body temperature. Water is critical for digestion and the optimal performance of organs. It also lubricates joints (Student Nutrition awareness campaign).

The total amount of water present in the body is affected by various factors including age, sex, and definitely the weight of the individual. For an adult male, about 60% of his total body weight is made up of water; for example, a healthy hydrated man who weighs 75 kilograms will be made up of about 45 liters of water. This water is known as the total body water (TBW). Total body water is scattered throughout the whole body and can be imagined as being contained in different body compartments or spaces (Gwinnutt and Thorburn). The spaces are separated from one another by membranes, which regulate the circulation of water among different spaces; this determines the amount of water that can be present in each of the spaces. The largest body fluid 'space' which makes up two thirds of the total body water (30 L) is within the body cells and is known as the intra-cellular fluid (ICF). The balance of one third (15 L) is found outside the cells of the body and is known as extra-cellular fluid (ECF). The ECF is further separated into different compartments; 10 liters are distributed between the body cells and this is known as interstitial fluid (ISF), 3.5 liters of ECF forms blood plasma in the circulatory system and is known as intra-vascular fluid (IVF), and the balance of 1.5 liters makes up trans-cellular fluid, which comprises cerebrospinal fluid (CSF), intraocular fluid, urine and the fluid in the bowel's lumen (Gwinnutt and Thorburn).

Most individuals don't take in enough water; this results in several disturbing symptoms that cause pain including headaches, loss of consciousness, back pain, pain in the joints, and kidney stones (Tennesen).

Benefits of water to the body

Drinking water is essential for many activities in the body. The benefits of water to the body include

• Distribution

Blood, 83% of which is water, is the body's distribution or transport system that enables the supply of oxygen, nutrients, enzymes and minerals that promote optimal functioning of the body cells. Blood also plays a crucial role in eliminating waste products by carrying them away from the organs to other sites.

• Lubrication

The presence of water in the fluids between internal organs and between the joints enables easy movement via the reduction...

This allows the body to easily move when walking.
• Digestion

The mucous lining the digestive tract is mostly made up of water and enables food to slide through the tract enabling its digestion. The salivary juices also contain water, which enables the movement of digestive enzymes to break down food.

• Temperature control

For optimal body functions, it is essential that the human body temperature is maintained within a narrow range. Water generally changes temperature by enabling the movement of heat. Therefore water in the body can not only store this heat but also move it to regulate temperature. Perspiration is another way in which water controls body temperature. This is because through sweat, heat is moved out of the body. One can lose almost a pint of water daily via the evaporation of water from sweat.

• Synthetic reactions

Within the human body there are many chemical and biological reactions that build enzymes and hormones which regulate various reactions in the body. Most of these reactions involve water.

• Waste removal

Upon the consumption of nutrients and oxygen, most of the cells ultimately produce waste products. Water enables the removal of these waste products by transporting them to kidneys and then out of the body through urine. Waste products are also removed through perspiration.

Water Intake and Sources

As human beings we ingest water as the normal plain drinking water, as beverages, and also in food. Water in food could be natural, from the food itself, or it could be added when cooking. It could also be produced in the process of metabolism. Many foods have water that is inherent: fruits and vegetables are made of 75-95% water; poultry, meat and fish are 50-65% water; while breads are about 35% water (Student Nutrition awareness campaign). All these different foods add up to the total water intake. Total water intake includes: water that is ingested in foods and beverages, and that which is produced in the process of metabolism of food which is approximately 350-400 mL/d (Grandjean). A sufficient intake of water is essential particularly for those who lead active lifestyles, because they lose substantial amounts of water through perspiration. Throughout exercise one should consume several glasses of water. It is also recommended that one should make a habit of drinking water throughout the day at regular intervals, even if one does not feel thirsty (Student Nutrition awareness campaign). Indeed, it has been shown that, by the time an individual 'feels thirsty', they are already in a state of 'mild dehyration'. As well, for those who are concerned with weight loss, another interesting factor is that 'feelings of hunger' may rather be signals that the body needs water.

However several medical journals released recently state that there isn't enough scientific evidence to back the claim that taking glass of water (with a capacity of eight ounces), eight times a day can bring about many benefits such as increasing the rate of weight loss, removal of toxins, healing dry skin, reducing fatigue or even speeding up the recovery rate from flu (Beck).

Intake and Output of Water and Electrolytes

To guarantee the best performance of all body functions it is important that the total body water is maintained within the desired volume, which is greatly determined by age, weight and sex among other factors. The distribution of the required amount of water to various 'compartments' is also important. How the body ensures that the fluid balance is maintained at the desired level is a process known as homeostasis. In a healthy body, waters (and by extension electrolytes contained in them) are constantly being lost. These have to be replaced to ensure that equilibrium homeostasis is maintained (Gwinnutt and Thorburn).

There are situations where the amount of water lost in the body is significantly increased e.g. when one suffers burns or has diarrhea. These can result in undesired distribution of body fluids resulting in inadequate or excess amounts in some of the compartments, for example, post- operative sepsis.

For a 75 kg man who is fully healthy, every day he will have a water output of about 2.5 liters; therefore an intake of equal amount is needed for maintenance of homeostasis (Gwinnutt and Thorburn). There are two kinds of fluid loss, sensible and insensible. Sensible fluid loss is that which can be observed and quantified, for example urine output; insensible fluid losses cannot easily be observed and quantified, and may include sweat or water vapor exhaled (Gwinnutt and Thorburn).

Sweat

How much one…