Research is limited on if dietary supplementation of collagen is effective at improving joint/skin health and much of the research is funded by the companies that produce it so more research is needed. Collagen is broken down into amino acids in the stomach so there is not much risk to the supplements but the marketing of it is pretty much hype.

https://www.hsph.harvard.edu/nutritionsource/collagen/

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Eating collagen, smearing it on your face, rubbing it into your hands, does absolutely nothing. When you eat it your digestive system breaks it down into amino acids as with any other protein.

Your body (fibroblasts) synthesizes collagen from amino acids, primarily glycine-proline-X or glycine-X-hydroxyproline. It makes as much as it needs or as much as it can. You don't push more into your cells through consumption or osmosis.

There is as much science behind collagen supplements or cremes as there is behind eating a bear's gall bladder for sexual potency.

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The limitation is whether supplements help at all. Some do, if you have a deficiency like iron. Newer ones we don't really know. But collagen is known to not absorb directly, it is broken down by digestion, so you are better off using the direct supplements it's made of like vitamin c and others.

If you have a collagen synthesis problem, that's generally not going to be solved by supplements because those are genetic and not dietary.

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Collagen is made from vitamin C? Tell me more!

Vitamin C is a necessary cofactor for one of the initial steps in synthesizing collagen. People with vitamin C deficiency (ie., scurvy) develop swollen gums and other signs of damaged connective tissue as a result of impaired collagen synthesis

No, but vitamin c is needed for collagen crosslinking, a process that strengthens your collagen. Deficiency leads to scurvy.

Hmm there is risk as arthritis can be induced by collagen, CIA(collagen induced arthritis). Collagen applied on the skin is not broken down by the stomach, the immune system also breaks down collagen.

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Collagen is broken down into amino acids which are not fungible (despite what some folks erroneously believe). Of particular note is glycine, which should be considered a semi-essential amino acid. That is to say, although we can synthesize some glycine, we can't synthesize enough to fully meet our body's needs.

The human body can produce glycine from serine, but only to the tune of perhaps 3g/day. Evidence suggests this is inadequate, and more like 10g/day of glycine is required. Thus having a dietary source of glycine, which would include collagen supplementation but could also be met by hipster bone-broth or just eating tendons (pho for the win!).

https://pubmed.ncbi.nlm.nih.gov/20093739/

https://pubmed.ncbi.nlm.nih.gov/23615880/

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The breaking down of collagen in the stomach is absolutely not established. In fact I believe individual collagen molecules are quite stable at low pH. Many proteins are pH stable and resist various forms of degradation during digestion. A notable case is the proteins making up gluten, which freely travel to the intestines and are the cause of celiac disease.

This is not established. Several studies point towards dermatological or joint health application for instance.

https://europepmc.org/article/med/30681787?crsi=662497074&cicada_org_src=healthwebmagazine.com&cicada_org_mdm=direct&client=bot&client=bot

https://link.springer.com/article/10.1186/s12937-016-0130-8

https://www.iomcworld.org/open-access/efficacy-of-oral-collagen-in-joint-pain-osteoarthritis-and-rheumatoid-arthritis-46863.html

This is incorrect. Collagen is not fully degraded during digestion and polypeptides do enter general circulation. The implications are unclear but there are several studies and meta analyses which point towards applications.

https://pubmed.ncbi.nlm.nih.gov/29467346/

https://pubs.acs.org/doi/10.1021/acs.jafc.6b05679

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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I'm happy to be corrected. Mostly I wanted to push back on the myth that proteins are somehow digested into some sort of universal protein sludge that's completely interchangeable.

My primary point is that we get glycine from collagen and that we need it because we can't make enough. I'm sure your expertise exceeds mine, but do I have that right?

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Collagen is digested just like any other food: very simply put, your body breaks it down into its constituent parts and uses those parts in a manner that the conditions in your body demand. The thing is, a lot of tissues in your body are built from the same kinds of substances, so once you digest that collagen, there is no guarantee your body will use its constituent parts to create more collagen. That doesn't mean eating collagen is meritless: it contains valuable amino acids. But your body isn't necessarily going to use those amino acids to create the same kind of connective tissue.

Cooking meat denatures the proteins that it holds, which actually helps their bioavailability. There is the thinking that cooking the hell out of something will reduce the amount of usable protein, but I don't remember ever seeing any hard data about this.

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But if you eat collagen, wouldn't it break down into the same amino acids that it could later be rebuilt from?

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Your body is constantly breaking itself down, catabolism, and building itself up, anabolism. Your body breaks down its own, endogenous, collagen and builds it up. By consuming collagen, your body can break it down rather than breaking down your endogenous collagen. The metabolites may or may not be used to build new tissue, but the benefit from it is supposed to be by decreasing catabolism without affecting anabolism.

I thought something similar, but with amino acids. I thought they would be directly used to make new proteins. After me wasting ten minutes of class time arguing with my teacher, this is how she explained it to me. The end results of metabolism may be used to build new amino acids, or in this case collagen, but the value comes from decreasing catabolism.

Are you not bothering to read some of the links that others have provided, that demonstrate that collagen may not be completely digested as most proteins are, and collagen derived polypeptides can indeed enter the circulation and are measurable? And that there is accumulating evidence from clinical trials that oral collagen supplementation likely indeed has objectively measured affects on skin and wound healing?

It would, but that's no indicator that it would be rebuilt into the same proteins, especially not targeting a specific area.

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We know that oral collagen supplementation likely does have objectively measured *effects on skin and wound healing, as is true with supplementation of other proteins, and there is a lot of clinical data that presumes that this is a result of the amino acid makeup of various proteins. I haven't seen a link in this thread that offers a lot of supporting evidence to the theory that that collagen in = collagen created, necessarily, aside from that Japanese study, which appears to have been conducted by scientists at FANCL Corporation, whose entire business is cosmetic and dietary supplements (that's not to say that the science is bad, but the conclusion is, shall we say, "less than unbiased").

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A legitimate question, that i have asked myself many times as well.

there should be no reason to assume it has any effect on the body, since its only being digested into peptides/amino acids.

its not completely unthinkable that it may still have an effect, through some sort of mechanism that we are just not aware of yet (maybe a bit like BCAA's boost Protein Synthesis, despite being "just some amino acids"), however that remains yet to be proven. And until then i will not recommend taking them, since they are quite expensive.

It's unclear - the mechanism is far from understood. We get glycine from almost any protein source so that's definitely not it. But oligopeptides can definitely have hormonal effects so who knows, maybe degradation products of collagen exert hormonal effects which lead to increased synthesis. Obviously totally hypothetical

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Agree that these studies using collagen-derived small peptides do show multiple measures of clinical improvement, and that it is difficult to show collagen peptides in = collagen created = clinical improvement.

Ideally such trials would be controlled with similar small peptides but distinct from the amino acid content of the experimental peptides; and unfortunately the trials I’ve looked at so far are controlled with starch-based materials.

However, as much as I laughed at this topic 20 years ago, I’m slowly coming to the conclusion that there might be something here. More time will tell

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obviously this is a hot topic and while there are some human studies, the rodent ones should be taken with a grain of salt. Collagen isn't in a typical rodent diet so it makes sense they haven't evolved to digest it the same way that humans can digest proteins. Factor in cooking and the picture gets even muddier.

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There is not officially a collagen RDA, but it is believed by some people that the modern diet is deficient in collagen (or collagen amino acid precursors). Some people take collagen supplement with the objective to counteract the natural decline in production with age. Collagen is not only used in the skin, but also by the vascular system for structure and flexibility.

As for absorption, some peptides do survive the trip through the stomach. Collagen powder is a convenient way to get the amino acids in the correct proportions that can replace less convenient methods like bone broths. Protein powders do not have the correct ratio.

I'm with you - collagen is great for you, I'm just here to make sure we're advocating for all dietary proteins, including collagen, especially for the folks in the cheap seats.

Anecdotally, I've been eating a very protein-rich diet for several years (averaging roughly twice what is recommended daily), and have also burned myself cooking dozens of times in that span. I have zero scarring. 🤷

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The second "study" was by a supplement company and used self reporting of pain (WOMAC). Zero evidence to suggest the collagen supplements drove that outcome.

Are the others any better?

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?

> 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.

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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