Nitrogen balance studies were used historically to determine protein requirements by analyzing nitrogen in food and bodily excretions.

“And they did what are called nitrogen balance studies, which today the protein community despises and says this is a horrific way to determine protein needs. But in the day was super clever.”

“And they took these conscientious war objectors and put them in these suits for months and they lowered their protein to zero. At which point they realized, "Wow, this is fascinating. The losses that you have from protein decrease as you lower your protein to zero because your body realizes you need to be more efficient with what you had."”