Keeping hydrated – why water matters
Keeping our body hydrated is something that we generally take for granted, but the importance of daily water intake cannot be stressed enough: our bodies are made up of two-thirds water and it is an essential nutrient used in all our cells, organs and tissues to help regulate temperature and maintain other bodily functions. We can survive for weeks without food, but only three days without water.
We lose water through breathing, sweating and digestion, which is why it's important to continuously rehydrate, both by drinking plenty of water throughout the day and eating foods that contain water, mainly fruit and veg. The more active we are, the more we breathe and sweat, and the more we use our joints and muscles, the more water we need – hence why athletes need even more of it.
Water’s role in the body
- Water lubricates membranes – making every cell in the body plump and helping to retain their shape in order to carry out certain functions – dehydrated cells can’t function the way that they should do. Essential fats also help keep our cells perfectly shaped.
- Water strengthens the immune system by improving lymph movement, keeping a nice flow through the body to carry out waste products quickly and efficiently.
- Our blood is made up of 90% water, helping to carry nutrients and oxygen to every cell and tissue.
- It is necessary for all digestive, absorptive, circulatory and excretory functions, including removing toxins.
- Our body needs water to make proper use of water-soluble vitamins B and C.
- It is required for the maintenance of proper body temperature, through perspiration.
- Water is important for muscle strength and function.
Given how many roles water plays in the body, it’s important to avoid dehydration and unsurprising that signs of dehydration are varied. Some of the most common signs are:
- Poor memory
- Stomach discomfort
- Cold extremities
- Joint and muscle pain
- Excess body fat
- Fluid retention and bloating
How much water should we drink?
Generally speaking, if you drink enough fluid so that you rarely feel thirsty and your urine is colourless, or light yellow, then your fluid intake is probably adequate. As an overall guide, you want to be looking to drink around 1.2 litres of water a day, which is the equivalent of six to eight normal tumbler-sized glasses. This only applies for a normal day, not when you are working out, when you will need significantly more.
Tea, coffee and sugary drinks are not to be included in this quota. They are ‘anti-nutrient’, meaning they block the absorption of some vital vitamins and minerals. Tea and coffee also act as diuretics, encouraging the excretion of fluids and ‘drying you out’. The same applies to alcoholic drinks and explains why your head hurts the next day.
Water and working out
You can lose a lot of fluid when you exercise – up to a litre an hour – mainly through sweating and breathing.
If you don’t top these fluids back up, you can get dehydrated, leaving you feeling tired more quickly and unable to control your temperature as well as usual. You are also more likely to be susceptible to cramp, as water helps fuel and lubricate your muscles.
It can take time for fluids to be absorbed into your body. Drink steadily during the day and aim for around 500ml of fluid at least four hours before you exercise. In the 10-15 minutes before you exercise, top your fluid levels by drinking about half of this again.
During your workout, respond to your body’s needs – if you are thirsty…drink water. There is a sweat rate calculation you can do if you want to be more precise but don’t let this deter you from simply drinking if you feel thirsty:
The sweat rate calculation
- Weigh yourself before exercise (do this before going to the toilet).
- Weigh yourself after exercise.
- Compare the figures.
- For every kilogram of body weight you lose, drink up to a litre and a half of fluid.
After your workout, ensure you keep hydrating to put back all of the water you have lost; do not be tempted to drink alcohol or coffee given their diuretic properties.
Too much water – is it possible?
Although uncommon, it is possible to drink too much water. When your kidneys are unable to excrete the excess water, the electrolyte (mineral) content of the blood is diluted, resulting in low sodium levels in the blood, a condition called hyponatremia. Endurance athletes, such as marathon runners who drink large amounts of water, are at higher risk of hyponatremia. In general, though, drinking too much water is rare in healthy adults who eat an average diet.