How To Tell
So how can you tell if your body is using the protein for muscle or if it's turning it into excess glucose? Scientists have answered this question.
You see, amino acids contain nitrogen. And when amino acids are turned into proteins, the nitrogen remains in your body as part of the protein. But when amino acids are converted into sugar, the nitrogen is released and passes through to your urine.
So if you want to know if your food is being turned into protein or sugar, all you have to do is measure the amount of nitrogen in your urine!
This measurement is called Amino Acid Utilization, or AAU. Here's how it works:
If a dietary protein has an AAU of 100%, it means that there is no nitrogen in your urine and that the body is using 100% of the amino acids in that food to build body protein. That's great!
On the other hand, if a protein source has an AAU of 10% that means your body is only using 10% of the amino acids to make body protein. That means your body is turning 90% of those amino acids into sugar. Not good!
So what's the best source of dietary protein, with the highest AAU? Scientists found that it's breast milk, with an AAU of 49%. That makes sense, because babies need an efficient source of dietary protein. But we're not babies, so what's the next best source of protein?
The next best source of protein is whole eggs. Whole eggs have an AAU of 47%. But it has to be the whole egg. If you eat egg whites like many so-called health experts tell you to do, you will only get an AAU of 17%. Why? Because egg yolks contain the essential amino acid methionine. Take out the yolk, and you seriously limit the egg's protein-building value.
After whole eggs come meat, poultry, and fish. They're all equal, with an AAU of 32%. But it really goes downhill from there.