* It keeps your body cool. Your body releases heat by expanding blood vessels close to the skin's surface - this is why your face gets red during exercise - resulting in more blood flow and more heat dissipated into the air. When you're dehydrated, however, it takes a higher environmental temperature to trigger blood vessels to widen, so you stay hotter.
* It helps muscles and joints work better. When you're well hydrated, the water inside and outside the cells of contracting muscles provides adequate nutrients and removes waste efficiently so you perform better. Water is also important for lubricating joints. Contrary to popular belief, muscle cramps do not appear to be related to dehydration, but to muscle fatigue.
* When we are severely dehydrated our skin is less elastic. This is different from dry skin, which is usually the result of soap, hot water and exposure to dry air. However, sadly, drinking lots of water won't prevent wrinkles.
* Water helps cleanse your body, inside and out. Your kidneys need water to filter waste from the blood and excrete it in urine. Keeping hydrated may also help prevent urinary tract infections and kidney stones. If you are severely dehydrated, your kidneys may stop working, causing toxins to build up in your body.
You don't have to take your water au naturale, however. Some might prefer it in the form of tea, although too much tea may hinder the absorption of essential nutrients like iron. And there is also a chance that it will become an addiction.
Adding milk to it may reduce the quantity of antioxidants, making an otherwise healthy drink a source of inflammation and acidity, while too much black tea (and therefore caffeine) can cause side effects including headache, nervousness, sleep problems, vomiting, diarrhoea, irritability, irregular heartbeat, tremors, heartburn, dizziness, ringing in the ears, convulsions and confusion.
However, regular tea consumption may lower the risk of contracting Alzheimer's and other neurodegenerative diseases, research having established that drinking green and black tea improves cognitive scores among those with dementia.
The combination of caffeine and L-theanine in tea has been shown to improve reaction time, visual processing, memory and concentration. It even changes the way your brain is organised for more efficient information processing.