Water is the key to life, and it takes up a big proportion of our body mass: around 60 percent! Dive into other reasons why it’s important in today’s on body fluid compartments.

Total body water can be subdivided into two major compartments: the intracellular fluid, which is fluid inside cells, and extracellular fluid, which is fluid outside of cells.

Assuming that the total body water is about 60% of body weight, roughly 2/3 of that, or 40% is intracellular fluid, and the other 1/3 or 20% is extracellular fluid. This is known as the 60-40-20 rule.

Intracellular fluid is important for dissolving cations, which are molecules with a positive charge, and anions, which are molecules with a negative charge. The major intracellular cations are potassium (K+) and magnesium (Mg2+), whereas the major anions are proteins and organic phosphates like ATP.