Nutrition Science and Everyday Application - beta v 0.1

332 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
in their diet to balance the amount of protein used by the body, measured as the amount
of nitrogen lost from the body. The Institute Of Medicine used data from multiple studies
that determined nitrogen balance in people of different age groups to calculate the RDA for
protein.
• Nitrogen Balance– A person is said to be in nitrogen balance when the nitrogen
consumed equals the amount of nitrogen excreted. Most healthy adults are in
nitrogen balance. If more protein is consumed than needed, this extra protein is
used for energy, and the nitrogen waste that results is excreted. The lowest
amount of protein a person can consume and still remain in nitrogen balance
represents that person’s minimum protein requirement.
Figure 6.14. People are in nitrogen balance when they excrete as much nitrogen as they
consume.
• Negative Nitrogen Balance– A person is in negative nitrogen balance when the
amount of excreted nitrogen is greater than that consumed, meaning that the
body is breaking down more protein to meet its demands. This state of imbalance
can occur in people who have certain diseases, such as cancer or muscular
dystrophy. Someone who is eating a low-protein diet may also be in negative
nitrogen balance as they are taking in less protein than they actually need.
Figure 6.15. People are in negative nitrogen balance when they excrete more nitrogen than they
consume, usually because they are not eating enough protein to meet their needs.
• Positive Nitrogen Balance- A person is in positive nitrogen balance when a