Normally, approximately 2.5 litres of water is required daily for a fairly sedentary adult in a normal environment to replace the total loss of water that occurs though urine, faeces, skin and lungs.
This water loss needs to be replaced. One litre or so needs to be as water or other non dehydrating fluids such as cold herbal teas. A little under a litre will come from food intake. The body also makes about 300ml through its own oxidative metabolic processes.
If you don’t drink enough water, this is what happens.
1. Pulse rate and rectal temperature increases
2. Increase in respiration
3. Experience numbness and tingling in the fingers and toes
4. Increase in concentration of the blood
5. Reduced blood volume and more difficult circulation of the blood
The difficulty and problems of the blood circulation under such conditions leads to:
1. difficulties in breathing
2. gastrointestinal upsets
3. feelings of sickness and not wanting to eat
4. if it carries on for an extended period it will cause problems with muscle movement and unstable emotions
In an animal trial, restricted water intake led to irritablitiy and in some cases, bad temper.
Thirst
It has been demonstrated that under intense physical activity a male will only drink voluntarily around 50% as much water as what is required to replace losses from urine and sweat. Only after rest and food do the cravings for the required amount of water return to replace the fluid deficit.
Hot Drinks
After drinking hot liquids, the internal temperature of the body rises, resulting in sweating. This cools the body down. This is sometimes used in the practice of medicine when an increase in body temperature is required for a short time, or whether sweating is required. So it is preferable to choose cool or cold drinks rather than hot ones to replace fluid losses, particularly if hot drinks are the only types of drinks that are normally chosen.
Drinks containing sugar
During physical activities lasting less than 90 minutes, water is generally the beverage of choice, however, the inclusion of small concentrations of carbohydrate (6%-8% carbohydrate) have been shown to better sustain power output over water alone during physical activities that produce fatigue in 60 minutes or longer.