When I was a child, one of my favorite stories was the old fable about "stone soup." There are probably as many versions of this fable as it is years old, but the one I like best goes like this: In a time of famine, a group of weary travelers come into a small village looking for food. They, fill a large pot with water, put in a stone, place the pot over a fire, and announce they're making "stone soup." Curious villagers come out to watch. Soon, one villager who has a little meat volunteers to add it to the pot, another brings a few potatoes, another a couple of cabbage leaves. Before long, everyone in the village has put in what he or she can, and the pot is full. When the food is ready, villagers and travelers sit down together and enjoy a delicious and nourishing meal.
On the face of it, this old fable seems to be just another story. But for me as a nutrition researcher it has important lessons: If you take any one of the soup's ingredients by itself, you end up with very little of anything. But if, like the travelers and the villagers, you take a variety of ingredients and cook them together, you end up with a lesson in cooperation and a meal worth eating. The fable is a simple way to understand that for the body to function as best it can, it needs the right ingredients working together. These ingredients include water, carbohydrates, protein, fat, vitamins, and minerals. They make up the body's own "soup," and they fuel thousands of interactions and reactions among our cells that are essential to our health and well-being.
Just as there cannot be soup without liquid, human life cannot exist without water. In fact, depending on one's gender and age, the body is about one-half to two-thirds water by weight. Water participates in nearly all of the body's activities. It is the main component of nearly all body fluids, such as stomach juices, saliva, and urine. It helps us digest food, absorb nutrients, and rid the body of waste products. Water bathes our trillions of cells and helps keep them in their proper shape so that they can function effectively. It acts as a lubricant around joints, cushions body organs, and keeps eyes moist so that they can produce tears. One of water's most important responsibilities is to keep the body's temperature normal and within a narrow range. If the body gets too hot or too cold, it cannot survive.
Because water is such a vital ingredient, the body does all it can to keep a proper balance between...