A positive nitrogen balance means that a person's nitrogen intake exceeds the amount of nitrogen being excreted from the body. This is the body's natural anabolic state, and it means that the body is fully recovered and ready to build muscle.
Most macronutrients, including carbohydrates, fats and proteins, contain oxygen, hydrogen and carbon. However, only protein contains nitrogen, which is one of the most important elements needed for building and maintaining muscle mass. Since nitrogen is only contained in protein, testing a person's nitrogen balance is usually the easiest and most accurate way to determine the body's anabolic state. If a test shows that the nitrogen balance is negative, it means that more protein is being used than is being taken in, which is a sign that the person needs to increase his protein intake.
An improper or negative nitrogen balance can result from eating an insufficient amount of proteins or foods with poor-quality proteins. It may also result when a person's protein sources lack the proper balance of essential amino acids. When an improper nitrogen balance is present for any extended period of time, it results in the body consuming itself to supply the cells, tissues and organs with the necessary nutrients.