Imagine this scenario. You are lost in the dessert and spend the day wondering around aimlessly in the hot sun with no food or drink. Fortunately at dusk you stumble across a settlement. What is the first thing you will ask for on arrival? Water, not tea, coke or other stereo-typically flavoursome beverage. The body can survive a few weeks without food, but only a few days without pure water.
There are a number of properties that makes water indispensable for human life. The first is that it is a strong fluid. This is due to its polar nature. A polar molecule is one that has a slightly positive and negatively charged ends. This means that if you put lots of water molecules together, they arrange themselves in a manner where the positive end of one is facing the negative end of another. This creates an attraction force called hydrogen bonding. This attraction force alongside the bonding within the water molecule itself is what stops one water molecule being pulled or pushed away from its neighbour. We therefore say water has a high surface tension and explains why a 50 tonne boat can float on water! Water is within and surrounds all our cells and having a high surface tension provides a resistance to all the compressive forces placed on our bodies.
Secondly, water is a strong polar substance. So when we add a weaker polar compound (let’s say salt [sodium chloride denoted NaCl]) it attracts the opposite ends of the salt molecule (in a similar manner to the formation of hydrogen bonding described above). The strength of the attraction, between the positive part of the water molecule and the negative part of the salt molecule, rips the salt apart into its base components. The process we have described is dissolution and is what allows our bodies to break compounds down and recycle them into more useful products for our cells.
Thirdly, water is great at helping our bodies regulate itself. It prevents large swings in acidity / alkalinity in our blood as well as helping us regulate our body temperature. Our cells are very sensitive to change, they have narrow operating parameters and if we fall outside of the operating window they malfunction. As an example, if our body temperature rises by just 1.5oC we become feverish!
Water regulates our temperature because it has both a high specific heat capacity and a high heat of vaporisation. Simply put, water requires a lot of energy to heat up and to evaporate. An average human can tolerate a 0.5oC body temperature rise before we initiation cooling methods such as sweating, seeking shade, etc. Not much really. But if we have a fluid inside of us which can absorb a large amount of energy before it shows signs of heating we can survive. This is why our bodies crave water in warmer weather, it’s our cooling blanket.
Water is also an integral part of our second defence against overheating, sweating. As sweat forms a thin film over our skin it contacts the heat energy from the environment first. The film acts as a heat sink, absorbing the energy until it evaporates. The more energy it can absorb the less energy penetrates into the body. The less energy penetrating our bodies the cooler we remain.
It is for these reasons that staying hydrated is so important. Our bodies crave water not tea, coffee, squash, alcohol, etc. Why give it an inferior substitute when water is easily available and cheap. Various studies from across the globe estimate that between 50 – 75% of the population are dehydrated! This is crazy when water comes out of our taps! Anyway, we hope this article has gone some way towards convincing you to swap that mug of tea for a glass of water.