Water in your body is like the oil in a car. It helps everything work properly – from helping carry things in the blood, to lubricating joints, removing waste, being the environment for your body’s chemical reactions … the list goes on!
Extreme dehydration is obviously fatal, but even mild dehydration negatively impacts a person’s mood, energy levels and mental function. Research has shown that women have difficulty concentrating and suffer fatigue, and men experience a decline in mood and mental ability (ability to reason, learning and short term memory). Given that this happens with just 1.5% dehydration and we don’t typically feel thirsty until we are 1-2% dehydrated, it is highly likely each of us has suffered this more than once.
By the time hydration has fallen 2-3% the blood starts to thicken, putting a strain on the heart and cardiovascular system as it must pump harder to push the same blood volume around the body. Combine this with an intense bout of exercise where your heart is already needing to work hard to pump blood to rapidly deliver nutrients and remove waste from your muscles and you can see how dehydration impacts performance.
Within exercise, where you are using water at an accelerated rate to drive metabolic reactions, plus losing it in sweat to cool the body and need to rehydrate rapidly, drinking pure water may not actually rehydrate you fast enough! Ideally you want to be consuming fluids that are just a slightly lower concentration to the blood (i.e. has sugar and salts dissolved in it) and specifically containing sodium to help transport the water into the blood and body tissues. This will help the water you drink get to the blood and tissues that need it the fastest! This is the design of sports drinks and electrolyte tablets. Within exercise you want to aim to ingest 1.5x the fluids you are using and losing – this obviously involves some estimation, but an extra 0.5-1 litre per hour of exercise is often taken as a rough guide for your ‘average’ individual.
Outside of bouts of physical exercise, straight up water is a great way to stay hydrated – as a rough guide, drinking 1ml for every kcal you burn should be enough or, more simply, enough so that your pee is clear or very pale!! If it is not, drink more! Keep a large bottle close by your desk / sink / sofa / bed at home – keep it topped up with water, and keep sipping regularly through the day. Every office and home has a water supply, so there really is no excuse!!