A nutrient can be defined as a substance that provides nourishment that is essential for the maintenance of life and for growth. An essential nutrient is one that the body cannot synthesize on its own or not to an adequate amount—must be taken into the body from the outside in order for the brain and body to function properly. There are six major categories of nutrients: Carbohydrates, Proteins, Fats, Vitamins, Minerals, and Water. No surprise, water is considered the most essential nutrient because it is required for all body processes. The body is basically a solution of about 70% water. Within the body, estimated percentages vary based on the type of tissue. For example: Blood 83%, Bones 22%, Brain 75%, Brain cells 85%, Heart 79%, Kidneys 83%, Liver 86%, Muscles 75%, and so on. More tomorrow.