proteinHow short must peptides be to enter the bloodstream from the digestive system?
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Orally ingested amino acids can exit the digestive system and directly enter the bloodstream (I think). Orally ingested protein must first be broken down into aminos and/or smaller peptides before leaving the digestive system and entering the bloodstream. My question is: A chain of approximately how many aminos is small enough to directly enter the bloodstream?
I am pretty sure that di- and tri-peptides can directly enter the bloodstream, but where (approximately) is the cut-off line? I am aware that it may be different for different types of aminos and/or different chain-structures (straight chain vs. a chain with various branches, etc.), so I am just looking for a rough guideline.
Thanks
I am pretty sure that di- and tri-peptides can directly enter the bloodstream, but where (approximately) is the cut-off line? I am aware that it may be different for different types of aminos and/or different chain-structures (straight chain vs. a chain with various branches, etc.), so I am just looking for a rough guideline.
Thanks
By Chris Brown – almost 2 years ago
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That's a very good question. You are certainly correct that amino acids and di- and tripeptides can be absorbed directly into the portal circulation (for you non-science types, that means single amino acids, chains of 2 amino acids and even 3 are well-known to be absorbed from the intestine into the bloodstream).
It is generally believed that only a maximum peptide length of 3 amino acids can be transported by the specific peptide transporter (called "PEPT1") that transports peptides. Interestingly, some di- and tripeptides are absorbed faster than even free-form amino acids.
One additional reason that proteins don't get absorbed is also that very few proteins make it past the stomach intact because the acid and enzymes break them down into small peptides and amino acids.
Certainly, molecules of over 10 amino acids can be absorbed through some membranes in the body but the limit for the intestines is generally considered to be tripeptides.
Nutritionist and Supplement Specialist