How Much Protein Can the Body Digest?

How Much Protein can the body digest at once? That has been one of my most asked questions since starting Proteinfactory.com in 1998. My answer has always been, “well nobody really knows the answer”, “no scientific studies have ever been conducted on the AMOUNT of protein an individual can digest at once. In this new letter I will address that question in a short paragraph by protein research and scientist Dr. Siebrecht

A certain portion of the protein we consume is not absorbed by our body but degraded by bacteria in our intestinal tract. Sometimes up to 40% of the consumed protein can disappear during the process. Also, a portion of the absorbed protein which reaches our blood is not used for protein synthesis but for energy production. In that case, the amino acids are transformed into carbohydrates by the gluconeogenesis in the liver. The liver transforms excess amino acids into carbohydrates by the gluconeogensiss in the liver. The liver transforms excess amino acids into glucose (gluconeogenesis) and the nitrogen of the amino acids is turned into ammonia and excreted as urea via the urine. The more nitrogen is found in the urine the more amino acids have been burned for energy production instead of being used for their main purpose, protein synthesis. The lower the nitrogen excretion in the urine, the more amino acids have been used for protein synthesis. This is called nitrogen retention and the higher the nitrogen retention; the more amino acids have been used for building new proteins in our body. Studies from Boza have shown that the nitrogen retention is highest for hydrolyzed caseinate, higher than that from free amino acids or intact protein. That means that the amino acids from Hydrolyzed Caseinate are better and more rapidly absorbed having a higher bioavailability for protein synthesis than amino acids from normal protein and free amino acids.

Whether the peptides are absorbed by the mucosa and what the mucosa releases into the blood is still a question. The mucosa cleaves the peptides further into single amino acids and releases them into the blood stream. But if this was always true, all proteins would appear as free amino acids. This would not explain the different metabolic, physiologic and pharmaceutical response of our body to different proteins and peptides. It is more likely that some smaller peptides are entering the blood stream as such and then causing different metabolic reactions.