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 Water & Hydration

June 2010
Watering Down
Prof. Adrian Kennedy
The human body is about 70% fluids. Blood is 98% fluid. Our brain comprises 88% fluid; even our bones have over 66% fluids. We need water constantly to hydrate our organs.

Water is essential for digestion of our food, circulation of blood, maintaining body temperature, lubricating our joints and excretion of body wastes and toxins amongst other things.

What is a normal fluid intake?
According to the Institute of Medicine (USA), the average intake of water for a healthy and hydrated woman is 2.7 litres a day and that of a man is 3.7 litres a day. This comes from all beverages such as water, tea, coffee, fruit juices, colas, beer etc, as they account for 80% of our water intake, and foods account for the other 20%.

In hot climates how much fluids should we have?
Active athletes and those who work in hot environments are advised to have as much as 5-6 litres of fluid intake. The type of fluids taken is dictated by taste and habit, ranging from water to tea, coffee, fruit juices, beer, colas etc. For moderate climates of 30 °C, 30 minutes of exercise will result in a fluid loss through perspiration of 1 litre. This will in turn reduce the body’s physical and mental capability by 5 percent. Significant dehydration will result in cramping, dizziness, loss of consciousness and if not remedied –even death.

How can a person assess their fluid status?
Medically, the gold standard is to check the blood for serum osmolarity. This is not always possible and so the easiest method is monitoring urine. Usually the urine is straw coloured or pale yellow. Darker colours indicate a need of fluids. However some medicine and supplements also influence urine colour.

Bottom Line
Most newspapers and journals have emphasized the importance of drinking water and highlighted the diuretic effect of tea, coffee, beer, alcohol and carbonated drinks. However, it has been noticed that when people do reduce their consumption of diuretic drinks, they do not replace it with hydrating drinks. This results in a lower fluid balance in the body, resulting in dehydration. The bottom line then, is to ensure fluid balance by having sufficient fluid intake each day, even if it means having less hydrating fluids. The best thing to do of course is, to have water. The worst thing to do is, to have nothing.

Can we ever have too much fluid?
The answer to this is yes, but this very infrequently happens in adults. It is more common in infants who are given too much fluid (milk, water, fruit juice) resulting in excess urination and depletion of sodium, resulting in electrolyte imbalance.
So drink in moderation but do drink!
Prof Adrian Kennedy is Sr.Consultant, Wellness Rx, International guru on health, wellness and lifestyle medicine and guest faculty for Harvard Medical School, USA

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