The human body can last weeks without food, but only days without water. The body is made up of 55–75 per cent water. Water forms the basis of blood, digestive juices, urine and perspiration and is contained in lean muscle, fat and bones.

As the body can’t store water, we need fresh supplies every day to make up for losses from lungs, skin, urine and faeces. The amount we need depends on our metabolism, the weather, the food we eat and our activity levels.

Facts about water in our bodies

Body water is higher in men than in women and falls in both with age.
Most mature adults lose some 2.5–3 litres of water per day.  May be more in hot weather and with prolonged exercise.
Elderly people lose about two litres per day.
And the raspy feeling in your throat after some airtravel??
An air traveller can lose approximately 1.5 litres of water during a three-hour flight.

That water loss needs to be replaced.

Foods provide about one litre of fluid and the remainder must be obtained from drinks.
However !!!! when you eat a lot of veggies and fruits, you probably more than double that.
If at the same time you stay away from breads and pastas, you'll probably do even better.
Water is needed for most body functions:
It is needed to:
Maintain the health and integrity of every cell in the body.
Keep the bloodstream liquid enough to flow through blood vessels.
Help eliminate the by products of the body’s metabolism, excess electrolytes, for example sodium and potassium, and urea which is a waste product formed through the processing of dietary protein.

And if you don't think eliminating waste is enough of a reason, it also helps:
Regulate body temperature through sweating.
Keep mucous membranes moist, such as those of the lungs and mouth.
Lubricate and cushion joints.
Reduce the risk of cystitis by keeping the bladder clear of bacteria.
Aid digestion and prevent constipation.
Work as a moisturiser to improve the skin’s texture and appearance.
Carry nutrients and oxygen to cells.
Serve as a shock absorber inside the eyes, spinal cord and in the amniotic sac surrounding the foetus in pregnancy.

Yes, also as shock absorber for the spinal cord and lubrication for your joints.
Glucosamine and Chondroitin alone will not keep your joints healthy.
You have to make sure you meet your daily water requirements

In other words, you can live a fantastically healthy life, eat all the right stuff, make all the right moves, but if you don't drink enough, it is all for nothing. Your body will struggle to make it all work and eventually fail you.  Or maybe you should
acknowledge  that you have failed your body.
Realize that the Healthindustry does not make any money on your proper water intake. How often did your doctor ask you how much water you drink?
Water - a vital nutrient ??
But 8 Glasses a day??
Apparently that was another fallacy produced by one of the biggest frauds in the history of nutrition : Dr. Frederik Stare