The liquid of life

Your health

By Dr Gita Mathai
  • Published 27.06.18
Illustration: Suman Choudhury

Water makes up 75 per cent of the body weight of an infant and 55 per cent of an adult. Our body is composed of multiple complex cells which contain enzymes, electrolytes and electrical charges. All these function only in the presence of water. "Fasting unto death" (for political or religious reasons) will take two months if only food is avoided. It will take seven days or less if water is also withheld.

The exact amount of water required for healthy existence has not been accurately studied. Roughly, the amount required varies with age from around 700ml (1 cup=250ml) a day for infants to 3.8 litres (16 cups) for lactating women. Not all this fluid has to come from water.

Infants get much of their fluid requirement from milk. The electrolyte composition of breast milk is ideal for babies. Any tinned formula has to be reconstituted precisely as advised (usually one flat scoop for 30ml of water) Adding more or less powder will cause variations in the electrolyte composition. The sodium content can go up and down (hypo or hypernatremia, respectively), as the infants immature kidneys cannot regulate this effectively. After weaning, water comes from food, juices and, later in life, from tea and coffee.

Aerated cola drinks are widely advertised as the ideal way to quench thirst on a summer day. Many of them are hypertonic so though the thirst is initially quenched, it is followed by a desire to drink more! Since these drinks contain sugar, consumption elevates the blood sugar (bad for people with diabetes). It then gets deposited as fat, adding to the expanding waistlines of the adult population.

There is no proven scientific benefit to drinking two to three glasses of water on an empty stomach first thing in the morning. Naturopathy says it cleanses the body. It does activate your gastrocolic reflex and prevent constipation. Otherwise it is better to sip water at room temperature all through the day. Ice cold water is less rapidly absorbed. Water should be drunk an hour before or two hours after meals. If it is drunk just before, it dilutes the gastric juices, making them less efficient.

The amount of water an adult needs depends on body composition (muscle:fat) outside temperature, humidity and level of activity. A labourer or marathon runner requires more fluids than a sedentary office worker. Before a workout, drink two cups of water to hydrate yourself. An active workout requires one cup of water every 20-30 minutes.

Older people may not be able to regulate their fluid intake relying on thirst alone. They may need to consciously drink water. School and college going youngsters (particularly girls) may suppress their thirst as they do not wish to use the restroom.

High coloured urine does not necessarily mean dehydration. The colour may be due to natural colours or additives in the food.

You can overhydrate by drinking too much water. This results in low sodium or hyponatremia. Headache and fatigue can be followed by muscle spasms or convulsions. Sportspersons can prevent this by adding a pinch of salt to their water or consuming isotonic sports drinks.

Dehydration is more dangerous. Concentration becomes poor, reaction time is increased, learning, memory, and retention are poor, and there may be mood swings. As dehydration progresses, organs can shut down, resulting in death.

Women should be conscious of their fluid intake during pregnancy as dehydration, especially in the last trimester, can precipitate urinary tract infections and premature labour. After delivery, good hydration means there is adequate breast milk for the baby.

The writer is a paediatrician with a family practice at Vellore and author of Staying Healthy in Modern India. If you have any questions on health issues please write to