Foods - Water - Requirements

You typically require 1.9L/2 quarts water daily to support proper function. Approximately 0.9L/1 quart is obtained through food while an additional 0.9L/1 quart must be consumed separately. This quantity increases for physically active people or those living in warmer climates. For more information, see Optimal Absorption, below. Serious dehydration can occur with a loss of only 5 to 10 percent body water, while a 15 to 20 percent loss is often fatal.

As we age, we "dry-out" somewhat and lose our desire for thirst. While a newborn is 75 to 80 percent water, people between the age of 65 and 70 are typically composed of only 50 percent water. This is reflected in stiff joints and reduced saliva flow. For this reason, optimal water consumption is recommended throughout life and well into the retired years.

When internal water content decreases, blood volume drops, salt content slightly increases, and saliva production drops. This series of events triggers a chemical and hormonal process inducing a sensation of thirst that is relieved through the consumption of water or other fluids. When you are thirsty, your kidneys also conserve water by redirecting it back into the bloodstream, resulting in increased urine concentration.