Dehydration can have dangerous effects on your body, including nausea, weakness and muscle cramps. At its most extreme, unconsciousness and organ failure can occur. Dehydration begins at the level of cells, where salt and sugar can effectively suck cells dry. This drying out of cells has important effects on cellular structure and function that lead to the severe symptoms of dehydration.
At the Cellular Level
Cells can be thought of as sacks of water containing dissolved salt and sugar. They are separated from the bloodstream by a plasma membrane, which surrounds cells and prevents salt and sugar from moving freely between cells and the bloodstream. Water, on the other hand, easily passes through the plasma membrane and naturally moves from where the concentration of salt and sugar is low to where their concentration is high. So, if salt and sugar are added to the bloodstream, for example by eating salty or sugary foods, water will move out of cells and into the bloodstream. The result is that cells are left dehydrated.
The most noticeable effect on cells of adding salt and sugar to the bloodstream is that it makes cells smaller. A normally functioning cell is 70 percent water by volume. When a large portion of that water moves out of cells and into the bloodstream, cells lose much of their volume. This effect can be seen just by stepping on a scale. Because water in the bloodstream is lost from the body through sweat and urine, dehydrating cells actually causes your body to “shrink” in the form of weight loss.
Communication between the nervous system and muscles is dependent on differences in the concentration of salt between muscle cells and the bloodstream. If a large amount of salt is added to the bloodstream, the salt balance that the nervous system depends upon can be thrown off. In particular, adding salt to the bloodstream makes it harder for cells to receive signals from the nervous system. This is why muscle cramping is often experienced by people suffering from dehydration.
Dehydrating cells by consuming too much sugar can actually prevent cells from utilizing that sugar for energy. Cellular respiration, the process by which cells produce energy from sugar, requires water in addition to sugar. If enough sugar is added to the bloodstream that cells run out of water for cellular respiration, energy production begins to shut down. This loss of energy production by dehydrated cells is why fatigue and weakness are common symptoms of dehydration.