Nutrition is the science of food, its use within the body, and its relationship to good health. It includes the study of the major food components—protein, carbohydrates, fat, vitamins, minerals, and water—and more than fifty specific nutrients of which are composed. Nutrition is vital to the good health of all people of all ages. When you eat, you are doing much more than simply filling an empty stomach. The food you take in ultimately feeds all the cells of the body as it makes materials for bones, skin, hair, muscles, etc. And provides the fuel for efficient operation. Too little food or too much –or worse, too much low-nutrient food – tends to lead to poor health. We now have evidence that poor nutrition may be linked to many serious diseases – among them are heart disease, stroke, and some types of cancer. Although most people are aware of the connection between good nutrition and good health, in recent years so many conflicting claims have been published about particular foods that the public has been left in confusion. Should you use saccharin in your coffee, on the theory that too much sugar is bad for you? But some studies have connected saccharin with cancer. And what about a cup of coffee? Isn’t caffeine a hazard? Perhaps you decide to switch to herb tea instead—and then read in the newspaper that some herb team although completely “natural”, also contains small amount of natural plant poisons. You can avoid some of these confusions., however, by studying what food is composed of and how it acts in the body. Good nutrition, as you will see, is not simply a matter of avoiding any one harmful food or filling up on any supposedly good food. We know that several types of food work together to produce good health.