You must have water in your diet. It is brimming with minerals and electrolytes, and you can’t live without it. Water is a solvent. It dissolves other substances and carries nutrients and other material (such as blood cells) around the body, making it possible for every organ to do its job.
A healthy body has just the right amount of fluid inside and outside each cell, a situation medical folk call fluid balance. Maintaining your fluid balance is essential to life. If too little water is inside a cell, it shrivels and dies. If there’s too much water, the cell bursts.
Your body is mostly (50 to 70 percent) water. Exactly how much water depends on how old you are and how much muscle and fat you have. Muscle tissue has more water than fat tissue. Because the average male body has proportionately more muscle than the average female body, it also has more water. For the same reason — more muscle — a young body has more water than an older one.
You definitely won’t enjoy the experience, but if you have to, you can live without food for weeks at a time, getting subsistence levels of nutrients by digesting your own muscle and fat. But water is different. Without it, you’ll die in a matter of days — more quickly in a place warm enough to make you perspire and lose water more quickly.
You need water to
Digest food, dissolving nutrients so that they can pass through the intestinal cell walls into your bloodstream, and move food along through your intestinal tract.
Carry waste products out of your body.
Provide a medium in which biochemical reactions such as metabolism (digesting food, producing energy, and building tissue) occur.
Send electrical messages between cells so that your muscles can move, your eyes can see, your brain can think, and so on.
Regulate body temperature — cooling your body with moisture (perspiration) that evaporates on your skin.
Lubricate your moving parts.
As much as three-quarters of the water in your body is in intracellular fluid, the liquid inside body cells. The rest is in extracellular fluid, which is all the other body liquids, such as
Interstitial fluid (the fluid between cells)
Blood plasma (the clear liquid in blood)
Lymph (a clear, slightly yellow fluid collected from body tissues that flows through your lymph nodes and eventually into your blood vessels)
Bodily secretions such as sweat, seminal fluid, and vaginal fluids
Urine
