Why can't humans drink salt water for hydration?
Humans cannot drink salt water for hydration because salt water is hypertonic, meaning it has a higher concentration of salts and minerals compared to our body's cells. When we consume hypertonic solutions, like salt water, our bodies try to balance the concentration of solutes through a process called osmosis.
Osmosis is the movement of water molecules across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration. In the case of drinking salt water, the higher concentration of salts in the water draws the water out of our body's cells and into the digestive system to balance the concentration. This results in dehydration and can lead to further health complications.
To understand why we can't drink salt water, we need to understand the concept of tonicity. Tonicity refers to the concentration of solutes in a solution relative to the concentration of solutes inside our body's cells. There are three types of tonicity: hypertonic, hypotonic, and isotonic.
- Hypertonic solution: A solution with a higher concentration of solutes compared to our body's cells. It causes cells to shrink as water leaves them.
- Hypotonic solution: A solution with a lower concentration of solutes compared to our body's cells. It causes cells to swell as water enters them.
- Isotonic solution: A solution with the same concentration of solutes as our body's cells. It does not cause any net movement of water.
Salt water, or seawater, is hypertonic because it contains a higher concentration of salts, such as sodium chloride (NaCl), compared to the fluid inside our body's cells. When we drink salt water, the higher solute concentration in the water causes water to move out of our cells and into the digestive system.
As a result, drinking salt water actually dehydrates our bodies rather than hydrating them. The additional loss of water from our cells can lead to more severe dehydration, electrolyte imbalances, and in extreme cases, organ failure.
To stay hydrated, it is essential to consume water that is relatively isotonic to our body's cells. That's why fresh water is the most suitable and effective source of hydration for humans.