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Protein absorption: how does it happen?

Much more than consuming the right amount of proteins and managing to digest them, protein absorption, that is, being able to absorb them, is essential. Exogenous proteins from food sources such as meat, fish, eggs and chicken are the main sources of nitrogen for the body, and therefore need to be absorbed correctly. We sum up here how this process occurs. Read on to understand how protein absorption happens.

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Where it all begins

After being consumed and going through the digestion process, which takes place mostly in the stomach, proteins are transformed into amino acids, and peptides (dipeptídeos and trypties). Recent studies provide data on the absorption of some intact proteins. However, they are molecules of small size. Thus, physiologically, the greatest absorption is of amino acids.

These products generated after the digestive process are absorbed by enterocytes, more precisely because of the striated edge membranes mucous cells of the intestine. Absorption is the transfer of peptides and amino acids from the intestinal lumen into the cell, this process occurs throughout the entire length of the small intestine, being the most absorbed amino acids in the duodenum.

The transport of amino acids

The transport of these molecules can be done paracellularly or with the aid of sodium-dependent or non-sodium transporters. Most amino acids to be absorbed depend on the transporters that have affinity to sodium, when sodium joins the carrier, the affinity for the amino acid increases, it connects to the carrier and is transported to the inside of the cell. In addition to the entry of amino acids into the cell, some transporters when making this passage may also transfer to the outside of the cell ions and potassium by the Na/K-ATPase pump in the cotransport system.

Absorption speed

In addition, the absorption speed is influenced by the size of the amino acid, the greater its mass of the side chair and also its electrical charge the passage through the membranes happens faster. Not only the size, but also the type of amino acids determine the translocation speed. In other words, Indispensable amino acids, such as isoleucine, leucine and methionine, are more rapidly absorbed compared to others.

Clinical practice

It is not uncommon to intake free amino acids (L-amino acids) in the form of powdered dietary supplement, to the detriment of food consumption protein sources, from common sense that free amino acids will be better absorbed and directed exclusively to muscle synthesis. However, the consumption of these amino acids generates a competition of absorption and overload of the transporters, impairing the absorptive process.

In addition, when compared to the digestion and absorption of complete proteins, the peptides generated are more rapidly absorbed than free amino acids, provided via supplementation. In addition to supplements have most of the time high cost. Thus, natural proteins of good sources, offered via food should be the nutritionist’s first choice.

Watch the SINE video online with Prof. Stuart Phillips: Protein recommendations in aging: the mechanisms of need

Article: Protein Absorption in the Diet Jochems PGM, J Garssen, Van Keulen AM, Masereeuw R, Jeurink PV. Evaluating Human Intestinal Cell Lines for Studying Dietary Protein Absorption. Nutrients. 2018;10(3):322. Published 2018 Mar 7. Doi:10.3390/nu10030322

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