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97screamingcacti t1_j29cina wrote

Reply to comment by DooDooSlinger in If collagen is a protein, and proteins are broken down during digestion, why would collagen or collagen supplements be beneficial? Is it just hype? by skepticated

Even if the peptide is stable at low pH, there are many proteases and peptidases in the GI tract that break down proteins to be absorbed. If I remember correctly, only single amino acids can cross into the bloodstream, so whole ingested proteins never reach circulation. I am by no means a nutritionist, but knowing this I have a very hard time believing that collagen supplements do anything to increase the collagen levels in the body. I believe they are broken down just like any other protein

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TheActualUrtie t1_j2bofez wrote

I am probably misunderstanding this, but isn't mad cow disease caused by a protein? How does that happen if they're always broken down?

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CrateDane t1_j2d9qlb wrote

They're almost always broken down, but there are exceptions. In our gut, there is for example a cell type that's taking small samples of the proteins and longer peptides, in order to feed "information" to our immune system about what might be lurking in our gut. Unfortunately that includes prions. Some of the prions end up in neurons rather than the immune cells, and that's where the problem can happen. In principle it only takes one single prion to trigger the disease.

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CrateDane t1_j2d8xbo wrote

> If I remember correctly, only single amino acids can cross into the bloodstream

Small oligopeptides can also cross, via transporters (eg. SLC15A1) that can accept peptides of about 2-4 amino acids.

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