The role of water

Links: to the Properties of Water Internet Research (I am living in Singapore so library option is limited) There has been much debate over the years about the amount of water the human body needs to survive and maintain optimum health. Howard cites that “Water is a basic nutrient of the human body and is critical to human life”. (1) The human body can survive for weeks without food but only a few days without water. The amount of water that a human needs to consume varies with gender, age, weight and physical exertion. Why is water so important? Water accounts for approximately 60% of the makeup of the entire human body. The body can get around 20% of its water needs through food but the rest must come from drinking fluids. The human body is mainly constituted of just 4 elements, carbon, hydrogen, nitrogen and oxygen but it is the combination of one oxygen atom covalently bonded with two hydrogen atoms and its unique properties that make this tasteless, colourless and odourless liquid that make it crucial in the makeup and functioning of the human body. Water is often overlooked as a key nutrient unlike carbohydrates, proteins and fats as it does not provide energy. It however has its own unique and diverse properties that are essential in the functioning of the body. Water has a unique structure due to its capabilities of intermolecular hydrogen bonding. The water molecules are electrically neutral and because of this there is an unequal distribution of charge. This shift in charge is what attracts water molecules to each other. The oxygen is more electronegative than the hydrogen which makes it a polar molecule. When opposite charged ends of water molecules are nearby, they will attract other water molecules creating hydrogen bonds. It is these hydrogen bonds that are responsible for the adhesive and cohesive properties of water. The cohesion attracts the water molecules to other molecules and the adhesion enables the water molecules to stick to surfaces. The strong dipole created by the hydrogen bonding in water creates surface tension and is responsible for the capillary action transporting blood and other substances dissolved in it round the body through the vessels. Water is unique in the fact that it is known as the “universal solvent” because many elements can be dissolved in it. Water is used as a solvent for blood, tissue fluid and cytoplasm. The polarity of the water molecule allows it to ionize substances easily especially water soluble vitamins and minerals as they can hydrogen bond. The ions can be taken away from their original structures to form a solution. It is the charged nature of the water molecule that makes it stable and allows it to act as a solvent. Water is also crucial in maintaining the electrolyte balance within our bodies. These electrolytes are charged particles and help transmit electrical impulses for the functioning of the nerves and muscles. The main cations are potassium for water balance in cells, muscle and nerve action, sodium for water balance in the extracellular fluids, calcium for bone and tooth formation and magnesium for the transmission of nerve impulses and muscle contraction. These positively charged ions must be kept at certain levels to maintain the correct balance across cell membranes. If this balance is upset it can be life threatening. Water acts a good lubricant as it is a liquid property. It is required to lubricate mucous membranes in the gastrointestinal tract and to aid the digestion of food. A lack of water will result in the hydrochloric acid coming in contact with the stomach lining and producing stomach ulcers. Water is also needed to lubricate the intestines to facilitate the passing of waste through the intestines into the colon. It is the prime component of saliva which moistens the mouth and contains the enzyme amylases which allows the breakdown of food to occur. Membrane layers also contain water which allows organs to move slightly with body movement without being damaged. Lubricant is also found between joints so that the cartilage is able to provide a smooth surface for the bones to move on without any attrition. If this was not there then it would cause much pain and discomfort. A regular intake of water is needed as the body excretes water through respiration, urine, sweat and bowel movements as the body cannot store any excess. Water acts as a temperature buffer as the molecules have a high heat capacity and this makes them capable of absorbing heat without a large change in temperature. “Water in the body serves both as a carrier of heat and as a refrigerant that removes heat by evaporation”. (2) The amount of water needed by an individual varies especially if heat is involved. This is important as the body needs to regulate its temperature is at 98.6F. If this is exceeded then a unique cooling mechanism is triggered and hence sweating occurs which is the body’s natural cooling mechanism. If there is not enough water in the body to perform the cooling process then water is lost from the blood. Dehydration has serious implications on the body. It occurs when the body eliminates more fluids than it absorbs. When water levels in the body are reduced by just 1% a person becomes thirsty, 5% muscle strength decreases and by 20% death occurs. Liquids need to be consumed at regular intervals with the volume depending to activity levels to prevent this from happening to maintain the body’s natural balance. Whilst the discussion amongst health professionals continues regarding the volume of water needed to be consumed for the body to maintain optimum health, there is no doubt as Kravitz suggests that “the unique properties of water place limits on our physiology and anatomy while simultaneously providing the opportunities for physical activity, exercise and life as we know it”.(4)The human body relies on the structure of water and its properties such as its hydrogen bonding and polarity to carry out the essential functions on a daily basis. There is no other substance that can lubricate, regulate temperature, transport essential nutrients and act as a solvent. This is all possible due to the large dipole leading to hydrogen bonding. Without it one simply would not exist.