Human Biology and Water
The amount of water in the earth's environment never changes, whether it is as a liquid (fresh water, seawater, rain, tiny droplets in clouds), as a gas (water vapour) or in its solid state (snow, ice or hail). There is also water inside living organisms. Water continually circulates between the land, the oceans and the atmosphere. This circulation is called the Water Cycle or Hydrologic Cycle
The water cycle is fuelled by the energy of the sun. The heat action on the oceans etc causes the water to turn to gas and water vapour. This is called evaporation. As the earth warms currents in the air are created. These convection currents lift the water vapour into the upper atmosphere where it begins to cool forming tiny water droplets that form clouds. The water droplets the fall back to earth as either rain, hail or snow.
The water may evaporate directly from the land or water to return the form more clouds. It may run off to create rivers and streams to eventually flow to the sea. Some of the water soaks into the ground as is absorbed by vegetation these plants release the water vapour in to the air by evapotranspiration.
Water and the body.
Water is a biological necessity at a cellular level. The volume of water within the body decreases with age. In the womb the human body contains 80% water. As a baby the rate drops to 73%. In young adults the amount of water is between 65-70%. 70% of this is within the muscles and 50% in fat deposits.
Water is a special chemical. 2 Hydrogen atoms joined to a single Oxygen atom.
The Oxygen atom has a greater negative charge. This makes the water molecule bi-polar. This polarity enables water to act as an excellent solvent. Many inorganic molecules can be dissolved in water. This allows the cells to store energy as glycogen and allows many of the body's essential functions to be performed. Without enough water life is not possible.
Water also requires a lot of energy for its temperature to be increased. This allows the body to cope with a wide range of environmental conditions before problems arise. If little energy was requires to heat water then the cells would boil and burst.
The water in the blood enables the body to react to environmental factors. When we are too hot the blood is directed to the extremities (Vasodilatation) to aid cooling. This transports heat to the surface.
When too cold the blood is directed to the core away from the extremities to reduce heat loss (Vasoconstriction).
The most recognisable way water controls heat is the production of sweat. Sweat reduces body temperature when the water droplets evaporate from the skin surface.
Digestion and metabolism are both water-based mechanisms. Water is required to break the amino acid bonds to digest proteins etc. Several vitamins are water-soluble.
Water is used to eliminate waste products and toxins from the body. Water is also required for respiration. The small sacs in the lungs require water to enable the oxygen in the air to be dissolved in the blood and for Carbon Dioxide to be removed.
Water is also required for good mental function. Without adequate water the nerves cannot pass an electrical signal efficiently.
Water also baths the joints and keeps the hydraulic systems functioning properly.
At rest we use between 600 to 900ml in sweat alone. A fit person should drink at least 2-3l per day. However depending on behavioural factors and climate this can vary widely. In extreme heat and during heavy exercise 10l per day may not be sufficient. At least 75% of Americans are chronically dehydrated. The thirst mechanism is a very unreliable mechanism for gauging when to consume more water. 37% confuse thirst with hunger and therefore eat more food. This results in greater dehydration as they use more water for digestion.
Dehydration can be fatal in both hot and cold conditions when the blood loses fluid it becomes thicker and circulates slower and is harder for the heart to pump the blood. This results in an increase in heart rate. Lose of blood volume and extra cellular fluid causes the cells to shrink as water is removed to balance sodium levels. These changes can damage the cell membrane and lead to vascular problems like strokes and thrombosis. Losing 2% of body weight in water compromises your overall judgement by 25%. Body functions are severely limited at 10% loss. Mental emotional and physical processes are impaired.
Urine is the best indicator of your level of hydration. The average person should produce at least 1 litre per day. The colour should be clear to straw coloured.
To summarise:
Dehydration causes:
Headaches due to increase blood pressure and cellular shrinkage.
Constipation due to the blood diverting water to more essential functions.
Fatigue due to muscles not working as efficiently etc.
Confusion and emotional distress.
Spasticity due to the muscles cramping through toxin build up and cellular contraction.
Blindness.
Coma
Death.
Factors effecting dehydration.
Ambient temperature. The hotter it is the more water the body will use in temperature regulation. Consider rationing sweat by reducing workload in the hottest conditions.
Ambient humidity affects the speed of water loss.
Clothing it is important to dress correctly for the conditions. When the air temperature exceeds 37 degrees then the body must be insulated from the environment.
Smoking increases fluid loss.
Drinks to avoid are those containing caffeine and alcohol.
