In adults, 55% to 65% of body weight is composed of water. In infants, the percentage rises to 75%. Virtually every body process depends on water, and every cell, tissue and body fluid contains water. Composed of only one oxygen atom and two hydrogen atoms (H2O), water is an amazing substance.

How the Body Uses Water

If enzymes hold the keys to all our chemical reactions, then water is the medium where they all take place.

The blood, lymph fluid, digestive juices, urine, and perspiration are all mostly water. Gases and nutrients are carried in the watery medium of the blood.

Wastes are removed from the body in urine and stool which are mainly water. Even stool, which seems solid, is 70% water.

A flow of electricity is required for nerve impulses and muscle contraction. The minerals responsible for these electrical impulses require a water solution to send their messages.

The body uses water to maintain a constant body temperature because it takes a great deal of energy to raise the temperature of water. That’s why your internal body temperature remains at 37°C even when you are outside on the hottest summer day. Perspiration is the body’s refrigeration system. Water on the skin evaporates and releases heat from the body.

Water is essential to the build-up or breakdown of carbohydrates, proteins and fats. Every time an enzyme goes to break off a sugar, an amino acid or a fatty acid, a water molecule is needed to break the bonds. When our bodies build a protein, carbohydrate or triglyceride a water molecule is removed for every amino acid, simple sugar, or fatty acid that is added to the chain.

Water Requirements

We must provide sufficient water for all metabolic processes, and replace water lost in urine (1.5L), feces (100-200 mL), sweat (500-700 mL), and water vapour in our exhaled breath (250-300 mL).

The normal sedentary adult requires six to eight 8-oz. glasses of water each day to maintain water balance. In hot weather and with increased activity, water requirements can increase five or six fold.

There are three sources of water: liquid drinks, food and metabolic processes.

Purified or spring water is the perfect drink to restore water balance. When exercising on a hot day, cold water with only small amounts of glucose or salts speeds the water through the stomach to the small intestine where it is absorbed and ready to help cool the body.

Fresh vegetables and fruits such as lettuce and tomatoes, oranges, watermelon, zucchini and cabbage have a high water content. That’s what makes salad or a juicy orange so appealing on a hot day. These foods are also low in calories.

When fats, proteins and carbohydrates are burned for energy, carbon dioxide and water are produced. A sedentary person derives approximately 350 mL of water from such daily metabolic processes.

Although we require a great amount of water daily and it is vital to life, water provides no direct nutritional value. In other words, water cannot produce energy, but energy cannot be produced without it!