Water - More is good or less is good??

Recently I watched a movie – Shamitabh. The leading man – named Danish - is a wannabe actor but is mute. Another man (our living legend Mr. Amitabh Bachchan) ‘lends’ his baritone voice to this aspiring actor; there is some futuristic techno-advancement that makes it possible. The actor would act, with lip sync, when the ‘voiceman’ actually speaks out the dialogues. It creates a hugely successful blend in the movie-world; thus goes the storyline.

In a scene, the man with the voice becomes boastful, and claims that it’s his voice (rather than the actor’s expressions) that made the actor the superstar. To justify his blabber, he says – “My voice = whisky; the actor’s acting = water. Water is nothing without the whisky (meaning, it can’t by itself give a ‘high’); but whisky doesn’t need any water; it alone is good enough to give a high.

However, this argument is busted when, in a later scene, another character asks him to read what’s written on the bottle of whisky – 44% alcohol + 56% water! Neat pure Whisky owes its very existence to water; without water, whisky can not be manufactured.

The point is – no form of life and no creation is possible without water.

Water is ‘life’ (jeevan’). Just as air and its oxygen is indispensable for life, water is the second most necessary element critical for life and its survival.

60% of the body weight is water. In a 70-Kg healthy adult, the volume of total body water (TBW) is about 42 L. 2/3rd of this body water (about 28 L) is intracellular fluid; 1/3rd is extracellular fluid (about 14 L).

Do we need to drink extra water to maintain good health?

There are ‘health columns’ written by ‘experts’ (very often by non-medical persons with average understanding of body functionality). On drinking of water, most experts advise a positive (if not aggressive) drinking of ‘x’ amount of water per day. For instance, irrespective of anything else, 10 glasses per day should be consumed. There are gadgets that even keep a tab on this daily intake.

Some points made to support this extra consumption are as follows –

(1)Extracellular fluid, which comprises of the blood plasma, is the communicator between cells. Extra water will help create a better cell-to-cell signalling.

(2)Excretory products are water-soluble (excreted into urine). Extra water consumption will generate extra volume of urine, with proper excretion of nitrogenous wastes.

(3)Cellular functions will be more efficient.

(4)Skin turgor will become better; Joints will have a finer lubrication (synovial fluid), and so on.

Let us come to the moot question? Should you be drinking water as an agenda? That is, is it in best interests to consume EXTRA water, in a pre-determined fashion, irrespective of whether body is asking for it or not?

As a student of Physiology, my take on this issue is slightly contrarian. Let us summarize a few aspects here.

The indicator most closely and directly linked to body water is the osmolality of the body fluids. Then there is blood volume. It may be noted that disturbances in osmolality can not be tolerated by the cells for prolonged periods. The Body water determines the osmolality of the body fluids. The osmolality is tightly and most efficiently regulated by two mechanisms – ADH and thirst. If there is even a small decrease in the water content of ECF, it will become hypertonic. Thirst mechanism will be activated, and the water consumed will normalize the osmolality. Thus, body demands water whenever it deems necessary. There will also be the action of ADH to conserve water from kidneys and rectify the osmolality.

There is a regular loss of water via various channels. Urine (1 to 1.5 L), feces (300-500 mL), other routes (heat transfer via skin, exhaled breath and speech) are the known channels of water loss. Generally, the water intake should be equal to the water loss, so that the osmotic equilibrium is maintained, between the various compartments, on a long term basis – The so-called “steady state” is maintained.

If plasma is hypertonic, and it is not rectified early from an external source, i.e., fluid intake, then the intracellular water will shift into the ECF. This will lead to shrinkage of cells. The cellular function may affect, at least temporarily, till a new osmotic equilibrium is achieved.

Let us also examine the converse scenario. If there is unnecessary water loading, even when body is not demanding, the ECF will become hypotonic. ADH release will be suppressed and there will be diuresis. However, ADH mechanism is responsible for only about 10-12% of the total water excretion or conservation. There may be a temporary shift of water from ECF into cells, till a new osmotic balance is achieved. The fallout of this would be swelling of cells.

Hypertonic plasma - shrinkage of cells - decreased surface area of the membranes;

Hypotonic plasma - swelling of cells - increased surface area of the membranes.

These are the possible scenarios. Now, with increased surface area of the cell membrane, there may be a temporary rise in the number of transport proteins; most notable being the Na+/K+-pump. It breaks down the ATPs even under basal conditions. Thus, a greater breakdown of ATPs may be expected with swelling of cells. (The number of Na+/K+-pump is influenced by many factors, viz., aldosterone, ubiquitins, and so on. Thus, it is not a very distinctive possibility unless these factors too get augmented.)

I have seen many practitioners of Ayurveda advocating a slight water deprivation. They suggest that a relatively lesser water means a lesser exudate formation during inflammation; this may limit the effects of inflammation and favour an early healing.

My take on unnecessary water “loading”:

There is a transport mechanism called BULK FLOW or ‘solvent drag’. (It is principally an opposite of osmosis; high solute or Na+ pulls water towards it by osmosis.) In bulk flow, water moves in bulk and it drags the solute (mainly Na+) along with it. This occurs in many instances, for instance, capillary filtration, CSF reabsorption, descending limb of Henle’s loop. Extra water in the ECF, even after diuresis, may cause a stronger solvent drag. This may put Na+ and other ions or solutes in a constant state of flux and even disequilibrium.

In summary, I believe, body demands water (in the form of thirst) if and when there is a shortfall. And, there is no additional benefit of an excessive water consumption just for the sake of it. Only when there is water loss (G.I. fluid loss, etc) that one should think of an aggressive replenishment.

The best approach should be to calculate the daily water loss (visible + invisible), and consume the amount equal to it, per day.

If less water is consumed (just about a glass or two less than the calculated), it will not result in dehydration. There will be shift of water between compartments, and body will try to achieve a new osmotic equilibrium for its fluids. More thinking and research is needed for this approach.

-Dr Vivek Nalgirkar