Ode to the water - the life giving fluid

This post is a collection of arguments about why is the water so important for life, health, beauty, and many other things. So let's start with the starters. The water is a medium in which nearly all chemical reactions of the body occur. It's essential to health and life, mainly because of the ability to form solutions and suspensions. Because it participate as both the reactant and the product, it is really the ideal medium for metabolic reactions inside the body.

When it comes to heat, the water can absorb or release a large amount of it with only a modest change of its own temperature. A characteristic that's called the high heat capacity. Plus the water is a major part of mucus and other lubricating fluids in the body. Let me name just a few of them: saliva, blood, milk, lymph, urine, bile, semen, sweat, tears, vaginal fluids, digestive juices, cerebrospinal fluid in your spine, and synovial fluid in your joints.

Now some more technical details of the body:

For the newborn, the water content of the body is about 75%. This will get down to about 55-60% by the second year of life, and stays roughly the same for the rest of the life. Otherwise, the adipose (fat) tissue is the only tissue in body without the water in it, so fatter people has logically less proportion of water in the body than lean people.

The kidneys are the organs that take care of filtrating the blood. Each day, they filtrate about 150 litres of it in women, and about 180 litres in men. That is about 65 times the whole volume of the blood in the body, even if  99% of it goes back to the bloodstream. Which redirects the rest of  1-2% into the urine, making about 1-2 litres of urine every day.

Mass of the kidneys is changing with the age as well, so for 20 years old person it weight about 260g, but in 80 years old person, it weights only about 200g. And the filtration rate decline by 50% between ages 40-70 too. Speaking of filtration rate, it is the quickness by which kidneys can filtrate, and it is 125 ml per minute for men, and 105 ml per minute for women.

Think of it as something over one liter in about 10 minutes. That brings me to my first flow diagram, which describe the situation, where you would about to drink one liter of water, and wait less than 10 minutes, and keep on drinking. The state that your body is going to get in is called the water intoxication.

To understand this flow diagram, it's good to mention one important rule: "The water follows the salt (NaCl), and the salt follows the water". Or in other words: "Where the salt goes, the water follows". So in the first stage sweating, vomiting, and diarrhea support the loss of the salt from the body. Moreover, any further drinking the plain water, is another factor contributing to that loss. This results in the decrease of Na concentration in the plasma (liquid portion of blood), and interstitial fluid, which is the fluid in the space outside of cells (or between cells if you like).


Decreased osmolarity means that because there is less salt, then there has to be less water as well (in the same space). So then cells compensate this event by taking up the water inside of them through the process called osmosis, and they become swelled. The state of swelled cells is basically defined as the water intoxication. If the intake of water was too large at the beginning, or it is continuing, then the convulsions, coma, and possible death can occur.


Water and the sea

Now, let's go back in the evolution and make clear about how really important the water is. By the definition, most of the life forms share the marine origin, meaning that all life basically comes from the sea. Moreover, the conditions inside of cells of most organisms living on the planet, are remarkably uniform.

Or, to put it another way, the fluids inside the most of our cells have the concentration of salt highly comparable with the salt water in the sea. Because the ocean presents itself as the very stable environment for development of organisms, those organisms living outside of the sea are quite sensitive to even slight changes in the salt concentration within their cells.

Basically, the biggest problem of any organism living outside the ocean, is to maintain this salt concentration inside of cells, which is achieved only by regular intake of water and salt. Ideally, the sea salt of course. Technically, kidneys can function on as little as 0.5 litre of water for a day or so, which they keep circulating over and over. By the end of the day, however, the urine can be as much as 1000 times more acidic than the blood.

Also, the fluid balance depends highly on electrolyte balance. Electrolytes are minerals, or inorganic compounds, which dissociate into ions - atoms, molecules, or compounds with the positive or negative charge. So the regular intake of those electrolytes with the water is essential, because normally, the water loss equals the water gain during the day. This way the body fluid volume remains constant and stable. The flow diagram bellow shows clearly how the body deals with the differences in input and output of the water during the day.

Generally, the recommended intake of water is about 1 liter for every 1000 calories of solid food. So it would mean that for recommended 2500 calories a day, you need to drink about two and half of liters of water. I know I'm getting my fair share of water everyday, and especially during the exercise, where you lose additional water through sweating and increased metabolic rate of the body. That increase can be even up to 20 times higher than the metabolic rate of the body during the rest. Along with up to 20 times higher of the oxygen consumption, but that's another topic for another post.