People can live for weeks without food. Without water, people will die within days. The human body is 50% to 70% water.

Information

Adults need at least two quarts, or eight cups, of water every day for good health. Children need four to eight cups depending on age and size. The easiest way to get water into the body is to drink it. Other fluids, and even some foods, have water. These can help meet daily water needs. Milk, fruit juice and even carbonated beverages are good sources of water. Drinks with caffeine do not help meet daily water needs. Caffeine is a diuretic and causes the body to lose water. Alcohol does not count toward meeting daily water goals.

One of the most important jobs of water is to maintain the body's fluid balance. This is a delicate balance of minerals. These minerals, called electrolytes, dissolve in water. Electrolytes include sodium, potassium and chloride. Electrolytes determine how much fluid stays in cells and how much remains outside cells. An imbalance is not healthy. Too much water inside cells is called "edema" or simply "fluid retention." Too much water outside cells is called "dehydration."

Many medical conditions and drugs affect fluid balance. The kidneys do most of the work of controlling fluid balance. People with kidney disease often have special needs in terms of the amount they must drink.