Final answer:
Positive nitrogen balance occurs when nitrogen intake surpasses output. It is expected in growth periods, pregnancy, and recovery from illness or injury as the body builds or repairs tissues.
Step-by-step explanation:
Positive nitrogen balance is a condition in which the intake of protein nitrogen (AA) exceeds the loss of nitrogen in the urine and feces, indicating nitrogen retention in the form of tissue protein. Three conditions where a positive nitrogen balance would be expected include:
- Growth periods, such as in children and teenagers, where new tissue is being formed.
- Pregnancy, where the developing fetus requires additional protein.
- Recovery from illness or injury, as the body repairs and regenerates tissues.
During these conditions, the body is effectively building and repairing tissues, which requires more nitrogen, therefore a greater intake of nitrogenous substances like amino acids is necessary for optimal health and development.