| Water and Body Hydration | ||||||||
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- Why is water necessary?
- How much water is required?
- Water in food
- Excessive water - fluid retention
- Deficit of water - dehydration
- Water intoxication
Why is water necessary?
Water is vitally essential for good health and proper hydration of all the cells and tissues in the body.
An adult's body weight is made up of between 50%-65% of water - thats a lot of water! Water exists in the cells, between the cells and within various organs and tissues.
Water is necessary for the following:
- In cells - water is necessary for the biological activity of proteins inside the cell
- Between the cells - water is necessary to enable information is exchanged between the cells
- Outside the cells - to ensure there is the right balance of the electrolytes (sodium, potassium, chloride) so that the cells and its surroundings have correct function
- Blood flow - blood is mainly made up of water (around 50%) and adequate hydration is necessary to enable proper blood flow
- In the colon - water is used to soften the faeces to allow them to pass through the colon and be excreted
- Various others - many, many other tissues and organs require proper hydration to be effective and healthy
Water is necessary to hydrate the body cells, so that they can move properly and in various tissues such as blood, to allow it to flow effectively
Water needs to be in a particular balance in the body for good health - not in excess and not in deficit.
Water is one of the macronutrient, as it is required in relatively large amounts to maintain good health (the other macronutrients are carbohydrates, protein and fats).
In general, adults are recommended to drink at least 8 glasses of water each day - more is required if exercise is performed, or if the weather is very hot.
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Water intake recommendation
The dietary reference intake (DRI) of water set by the DRI committee is:
- Adults - 1.0ml - 1.5ml per KCal expended
- Infants / Athletes - 1.5ml per KCal expended
The water intake for an adult on a 2,000 kCal diet is:
- 2 - 3 litres (or 7 - 11 cups) of water
Most foods contain water. The foods with the highest amount of water are:
Even cheese, pasta, legumes, poultry and meat contains some water.
Excess of water - fluid retention
Fluid retention is caused when there is an imbalance of the electrolytes (chloride, potassium and sodium) within the cells and outside the cells of the body and / or an imbalance of certain proteins and hormones.
Fluid retention is also known as oedema, which causes a reduced ability to deliver oxygen and nutrients to the cells and to remove wastes from the cells. A very bad result of this condition is that the body cells stop functioning properly and ill health ensues.
Deficit of water - dehydration
Dehydration is a condition whereby more water is excreted than that which is taken in. Dehydration often occurs frequently after vomiting and diarrhoea because that is when an excessive amount of fluid is lost very quickly and not replaced quickly enough.
Dehydration can be a serious condition if not treated properly, especially in infants, young children and the elderly.
Symptoms of dehydration are:
- thirst
- dry skin
- headache
- low blood pressure
- fast heart beat
- weakness
Dehydration needs to be treated quickly to replace the water that has not been consumed, or has been lost.
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Water intoxication (or Hyponatraemia)
This is a rare, but fatal condition where the body is overwhelmed with water that it cannot excrete the excess water through the kidneys. This condition happens when excessive water is consumed or when the kidneys are not functioning properly. Basically the body's cells drown within themselves as they become swollen with excessive water, which is not excreted normally.
The symptoms of water intoxication are:
- headaches
- blurred vision
- confusion
- convulsions
- death (in extreme cases)
Water intoxication would generally not occur unless an excessive amount of water was consumed (around 30 litres of water or more).
references
- McGuire M, Beerman KA, Nutritional Sciences: From Fundamentals to Food, 2007 Thomson Wadsworth USA
- Rolfes SR, Pinna K, Whitney E, Understanding Normal and Clinical Nutrition 7th Edition, 2006 Thomson Wadsworth USA
More information
To learn more, go to the official Dietary Reference Intakes web site.