Water Is Essential To Life
Why is Water (H2O) so essential to life?
Simply put, a few days without it and death from dehydration comes quickly (I know it’s morbid to think of it that way but it’s the truth).
All of our cells soak in water; it makes up nearly 60% of total bodyweight.
For example, a 100lb woman actually carries around 60lbs of water; a 200lb man carries about 120lbs.
Our water content depends on body composition because different cells contain different amounts:
- Bone contains 22%
- Adipose Tissue (fat) contains about 25%
- Muscle cells contain 75%
- Blood contains nearly 83%
Look to the next section for how these areas are so important for our body’s natural function.
The Roles of H2O
Water acts as a solvent, as a transporter, as a catalyst, as a lubricant, as a temperature regulator, and as a mineral source.
Solvent: In the body, it acts as a solvent to dissolve proteins and transfer them through the body.
Transporter: It transports nutrients to cells and carries waste products away from the cells.
Catalyst: As dissolved chemicals spend much of their time surrounded by water, it serves as the medium for a large number of intracellular metabolic reactions.
Lubricant: It lubricates joints and even acts as a shock absorber for the eyes and spinal cord.
Temperature regulator: Body water content and fluid exchange regulate body temperature. When body temp increases we begin to sweat.
Mineral source: Drinking fluids is an important dietary source of several minerals, including fluoride.
Estimating H2O Intake
Below are two equations that you can use to estimate how much water you need on a daily basis (this will change if you workout).
Estimating fluid needs by metabolic rate:
With this method, for every 100kcal of metabolic rate, you ingest 80-110ml of water.
So, for example, if you’ve got a BMR of 2000kcals, you require a daily intake of 1.6-2.2L of water/day.
Estimating fluid needs by bodyweight:
With this method, for every kilogram of bodyweight, you’d ingest 30-40ml.
So, for example, if you weigh 110lbs, you’d require 1.5-2L/day. And if you’re 220lbs, you’d require 3-4L/day.
Body Water Regulation
Body water and electrolyte levels are regulated by the balance between fluid intake and excretion through the kidneys.
Both thirst and kidney excretion are, in turn, influenced by pituitary hormones such as:
- adrenal hormones such as aldosterone,
- and concentrations of blood osmolytes.
These mechanisms signal thirst when body water volume is low.
They also signal urinary excretion when it is high.