Water. This most precious resource on Earth is the essence of life. It happens to serve a few physiological functions as well. Water catalyzes chemical reactions, transports nutrients, bathes the cells and lubricates the joints. It regulates temperature, moisturizes the skin, supports proper bowel function, cleanses and detoxifies. We can last several weeks without food, but only a few days without water.
How much of our diet should be made up of water? The human body consists of nearly 70 percent water, more in thin individuals. It follows by analogy that 70 percent of the dietary intake, by weight, be made up of liquids.
To replace the amount lost through urination, perspiration, breathing and bowel movements, authorities recommend 8 to 12 eight-oz. glasses of water (64 to 96 total oz., or 2 to 3 liters), and possibly more depending on the weather and one's activity level.1 This recommendation is based on the standard American diet (SAD), which is high in animal foods and refined grains, both of which contain very little water.
(To test the validity of this, conduct an experiment of your own: put a chicken breast, or a bagel, through a juicer and note the absence of any liquid whatsoever. Compare this with one large apple, which is 85 percent water and yields nearly a cup of juice. Better yet, don't try this and just trust us!)
Since the typical foods are so dry, the estimation is that only 20 percent of our water comes from the food we eat, and therefore 80 percent should come from beverages. But when consumed with meals water dilutes stomach juices and washes out enzymes, delaying digestion, so unless one were to chug entire liters of water between meals, the recommendation is excessive and impractical.
Drinking a gallon of water in addition to a day's worth of calories is inferior to consuming the equivalent amount of water packed naturally in food. In other words, the recommendation is in reverse: 80 percent of liquid in the diet should derive from what we eat rather than what we drink.
How to achieve this? Simple.
Emphasis should be placed on those foods whose make-up by weight is mainly water. What foods fit the bill? As a group, animal foods are low in water, as are nuts, seeds and grains.
Fruits and vegetables, on the other hand, derive as much as 90 percent or more of their weight from water. Watermelons, tomatoes, lettuce, eggplant and celery, just to name a few, contain more than 90 percent water. Apples, peaches and oranges are 85 percent water. Kidney beans contain more than 75 percent water. At 95 percent, a cucumber is almost pure water. One cucumber (300 grams; 50 calories) provides more than a cup of hydration!
Assuming an average water content for fruits and vegetables of 70 percent (an underestimation, clearly), each piece of fruit or cup of vegetables is the equivalent of 6 oz. of water. Ten servings of these foods amounts to nearly 8 glasses, mixed with vitamins, minerals and fiber, and without even one drop drunk.
What's more, the water in fruits and vegetables is naturally filtered through the roots and leaves, so all the worries surrounding drinking water – the fluoride, disinfectants, pharmaceuticals, pesticides, bacteria and other contaminants – are out the window. Fruits and vegetables are also a natural source of electrolytes, including potassium. This is not to say you should avoid drinking liquid, only that beverages are meant to supplement your water intake rather than be its main source.
Remember, the planet is mostly water, and so are we. And plant foods make three.