What is nitrogen balance
Nitrogen balance does not necessarily mean someone takes the same amount of nitrogen they use. Nitrogen balance is simply the measure of nitrogen output subtracted of the nitrogen input. Therefore, if someone takes less nitrogen than they are excreting, they are said to “negative nitrogen balance”.
A negative nitrogen balance is associated with malnutrition and / or over-training ie catabolic processes are overriding anabolic ones. Conversely, a positive value is often found during periods of proper and in particular on the nutrition and during resistance training acts as a stimulus for nitrogen / exercise proteins.
How to measure nitrogen balance
Nitrogen balance measurement is at best an estimate of the contribution of both nitrogen and excretion. Due to the incorporation of nitrogen in the urea, the nitrogen loss is usually measured using the urine, feces and nitrogen content sweat. Losses can also occur through exercise during exhalation by the errors that extend make it unreliable.
Other issues were found that light exercise increased the leucine oxidation without increasing urea production. If that is the case, then the protein needs for maintenance of muscle tissue can be underestimated. Other techniques which may be more accurate use tracer techniques using radioactively labeled tracers which are either ingested or infused.
For example, by injecting an amino acid with a carbon atom marked radioactively, a hydrogen atom or a nitrogen atom in an individual, it is possible to the amount which is necessary to achieve a balance with the amount excreted. It is then possible to measure all the oxidation of amino acids of the body and degradation by measuring the amounts of radioactive carbon or nitrogen in the breath or urine of the participant.
A new technique is now used in a number of studies examining the protein needs. This method is called indicator amino acids oxidation (IAAO). IAAO is based on the concept that when an essential amino acid is deficient for protein synthesis, including the indicator of amino acid, will be oxidized. With the increase of the contribution of the limiting amino acid, IAAO will decrease, reflecting increased incorporation into protein.
If you did not get that, try this analogy. We have a nightclub (your muscle) that many men in it (muscle fibers) so that the porters stop letting the guys (indicator amino acids) into the club. Therefore, there is an excess of guys outside the club who can not get in so they oxidized. However, if a guy is with a girl (essential amino acids) while they are complete (protein) and can enter the club … so, if we get a coach load of girls go down and go with each one of our excess guys we get less oxidized guys outside and incorporating into the club.
This really makes sense if you know anything about complete and incomplete proteins. In addition to this, we see that food higher in leucine give us a lower (good) IAAO. Studies using the IAAO method showed that casein has a higher metabolic availability (MA) than soy proteins, so it must be a good method. This method also found errors in earlier studies using other methods and the results are apparently contending that strength trainers have known for years.