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The 1961 paper "Protein Intake in Liver Disease"
Hi @david. that was a very well thought out and formulated answer. First I should probably mention that I'm not qualified to make specific claims about those cases of liver disease as I don't have much knowledge about them. I also think you make a pretty decent argument how this is relevant for the vitamin A depletion problem and am kind of impressed with that.
I still have a few counter-arguments or at least points of view I'd like to bring up though. First I would just like to clarify that I didn't intend the "what has this to do with vitamin A" question as criticism, I just didnt really see the relevance that much before what you just explained. About the chewing of the food I wonder how relevant it is?? I mean I know it's a very touted thing that has been a fad on an off for centuries, but is it really essential?? or is it more a question of not stressing? Mechanically the reasoning is sound but I wonder to what degree it has a substantial effect on the actual in vivo situation. With starches it is documentably so as the amylaze enzyms in spit definately can be shown to increase absorption of glucose. If the mastication have a major effect on protein uptake - even if it at least has to have some effect - I'm not that sure of. What I've seen of reserach suggests that the (individual) amount of hydrochloric acid seems to have a much larger effect. I'm only musing on the subject here though, but it's interesting.
The general trend of eating less protein and simultanously having poorer absorption seem quite universal. I would guess the world wide overconsumption of vitamin A would contribute to that- regardless of it having to be taken in to consideration after the damage is already done anyway.
About the carnivore diet I am not sure I agree with you though. As far as I know the main observation also commented on by Grant is the more or less absense of detox cycles and symptoms on carnivore, not the actual more effective elimination of vitamin A. Without interpreting Grant to much here I understood it in the way I percieve this myself -wether the elimination is actually completed or if it mainly gets out of the bloodstream where most of the detox setback/syndroms/symptoms occure. It's possible that is not the case but there might also be something about the constant ketosis and lack of fibers potentially that could make the body not rid itself of vitamin A in the same way. 100% on my own I reason that because the liver stores glucose, a lack of exogenous glucose would affect the liver quite profoundly and potentiall hold on to toxins, not sending it into the bloodstream. There is as far as I know no research on this. Main take away here is I think what is observed is that they dont get the detoxsymptom cycles much, but nothing about their actual vitamin a status. I assume though that at least protein intake will not be the limiting factor on the carnivore diet.
On the quote about the lack of research. That was my initial point. Not that this subject was irrelevant at all, but that there is no evidence presented that what they observe actually is an increased protein uptake. Not that it cannot be, but that we rather have no indication wether it is or not. If they had made the research to see if the probiotic strains modulated the immunesystem (which some do btw) and thus decreased inflamation and had observed the same results they could have stated that it was due to immunomodulation. So the fact that they were looking for increased protein absorption does nothing to prove that that was what was actually observed. It might, but also it might as well not. We simply dont have any data on it.
That diet does change gutbiom seems to be very well documented no doubt about that. I'm not sure though of the effectiveness of changing it, WITHOUT simultanously changing diet, by taking probiotics. It usually is only a temporary effect, not a cure, and treatment has to be repeated. THat's fine by me if it helps give relief. But there is also the problem that has been observed in research that implementing probiotic interventions consisting of only a few strains usually have the effect of upsetting the ecology of the intestinal ecosystem causing some strains to take over and with time encouraging things like candida overgrowth. The most healthy digestive systems seems to have a very wide set of bacterial strains, which is generally deemed the most reliant marker of a healthy bacterial gut flora. Thus for people with severe bowel problems the main hospital approach for this has been fecal transplants from people with especially healthy gut flora. (In sweden the whole system was dependant on ONE lady for many years as she was the only healthy enough donor they could get). Unfortunatly even that doesnt seem to stick. Now my point here is just to problematize the solution " add a certain strain" - not to say its all.... crap!
I have no proper knowledge about the possibility of ammonia overprodution though. Still I'm sceptical. It seems to me most people are eating a bit too little protein for optimal health. But on the other hand we are obviously as a species able to thrive on a huge variance of protein intake. I think the best example here is the Kempner Rice diet which Grant also mentions. Even if its not an optimal diet, it is an almost protein free diet (i.e. veery low), and still it made people on it permanently heal from both cardiac disease and kidney failure among other things. It was even done for many years (up to 10!) by some of his patients. (Grant usually contrasts just that diet to the carnivore diet). SO this make me think that it might be possible to get too caught up in the protein thing?? I dont know but its worth reminding oneself of. I myself eat a lot of meat and dont feel good without it, but that doesnt change the fact that some do.
I am not trying to reach a specific conclusion here, just maintaining that from this research it's hard to find out if this approach helps. Also I can't help but think, are there anyone at all on this "program"/diet that actually are known to have that kind of specific liver failure?? I never heard of it, but of course someone might. I still think it might be very few if there are someone. Not saying that makes it worthless, but it still makes it seem like a potentially irrelevant factor for the vast majority.
Hope this clarified what parts Im hesitant about concerning this. I got a bit caught up in this now as it was a well reasoned line of thought which I appreciate, but my initial point was simply that the research does neither confirm nor refute what it claims to inverstiage
Hi @henrik!
Thank you for the compliment and your commentary!
Excuse me for the long reply and feel free to only comment on what pleases you.
The idea with posting the original 1961 paper "Protein Intake in Liver Disease", was that I thought absorption of a sufficient amount of protein for a person, what ever that might be for any one individual, seems very important to regain health. But as they mention in that 1961 paper:
"Prior to 1940, a low-protein diet was recommended for patients with chronic liver disease. However, experimental and clinical studies during the next decade indicated that dietary protein deficiencies were frequently associated with the production of liver disease. Consequently, it was concluded that very large intakes of protein were essential in treating patients with liver disease. It has now become apparent that the truth with regard to protein requirements in liver disease lies somewhere between the two extremes."
Where one fits on the protein-need-spectrum (lower protein to higher protein intake) I think is very individual and would likely change over time. Excess protein intake can give some people problems such as excess ammonia or it might feed a dysbiosis. I think this is a trade-off problem, where there are many Pareto-optimal solutions depending on one's specific goals and preferences. I saw this good quote on trade-off optimization from this 2023 paper's introduction, "Visualization and analysis of Pareto-optimal fronts using interpretable self-organizing map (iSOM)" [I bolded only in the quote below]
https://doi.org/10.1016/j.swevo.2022.101202
"The basic paradigm in problem solving involving multiple and conflicting objectives is to understand and reveal their trade-off. In Pareto-optimal (PO) solutions, improvement of one objective comes only at the expense of at least one other objective. Thus, it is important to understand the trade-off between gain and sacrifice in objectives between two PO solutions before making a wise decision."
In comparison I don't believe increasing one's absorption percentage of protein has any obvious downsides more than giving less protein for bacteria to ferment in the colon and that one might need to eat less food. If it is the case it has minimal downside, then starting out with increasing one's absorption percentage of protein seems to be low hanging fruit for health.
I am not trying to reach a specific conclusion here, just maintaining that from this research it's hard to find out if this approach helps. Also I can't help but think, are there anyone at all on this "program"/diet that actually are known to have that kind of specific liver failure?? I never heard of it, but of course someone might. I still think it might be very few if there are someone. Not saying that makes it worthless, but it still makes it seem like a potentially irrelevant factor for the vast majority.
After it closes, the remnant is known as ligamentum venosum.
If the ductus venosus fails to occlude after birth, it remains patent (open), and the individual is said to have a patent ductus venosus and thus an intrahepatic portosystemic shunt (PSS).[4] This condition is hereditary in some dog breeds (e.g. Irish Wolfhound). The ductus venosus shows a delayed closure in preterm infants, with no significant correlation to the closure of the ductus arteriosus or the condition of the infant.[5] Possibly, increased levels of dilating prostaglandins leads to a delayed occlusion of the vessel.[5]"
I believe that long-term protein deficiency, what ever that might be for an individual, is important to avoid to be in good health. I don't think it necessarily means a high intake in protein but getting enough absorbed protein. I still think increasing the absorption percentage of protein by some of many methods seems like a favorable thing to do.
Ending my comment by reposting my simplified formula from an earlier comment (page 1 of this thread):
[Absorbed amount of protein (g)] = [Absorbtion percentage of protein (%)] x [Protein intake (g)]
PS. I think one of the main benefit of probiotics/beneficial bacteria is not what they do, but what they replace. Good bacteria can take up the place inside of our gastrointestinal tract instead of other types of bacteria that can be harmful to us.
@david Hi. No problem . I'm applyling a disclaimer in advance here that I might reply in several seperate posts due to time issues, but let's see.
To start with, the idea that it's only important to have sufficient but not necessarily high protein - i.e. the middle way in protein intake, sound reasonable to me. I take your first links which isn't really my "field" to be a - use individualized approaches, which I think is a very good idea. I also think I myself is an example obviously needing quite high protein intake (if that is the constituent of meat that I crave and not zinc or several others - probably a combination).
On the second link about "Methods for improving meat protein digestibility in older adults" I have several issues though. Not sure if you are basing it on that still but I have went through it now and see that it doesn't provide any evidence for protein absorption or anything like it, and nothing connected to the importance of mastication! They list a generalized effect of mastication on food absorption mentioning the digestive enzymes in the mouth as I mentioned, but nothing specific to protein. When it comes to actual protein digestion you will find further down in that article that they say as I mentioned it's largely down to hydrochloric acid, which conforms with the few human tests done, originally with a man in north america 100 years ago or so that had a whole in his abdomen so the doctors could watch the digestion of different foods in realtime!. They do mention that older people in Korea tend to undereat meat though they like it. This turns out to be mainly due to problems chewing due to bad teeth making them eat more soups and stews as they was easier to masticate and swollow, leaving the average meat consumption among that group at what's deemed an unsatisfactory level of 8.6%. I agree that's probably too low for most people. And they skip the part where economy and food culture might also reduce the intake. None the less, they don't report any malabsorption due to poor chewing only avoidance due to bad teeth. Then they list a set of mechanical an other ways to improve absorption. Mastication is not on that list. The closest they come is to use ground beef in stead of whole beef, which you could claim that mastication replicates. BUT alass it just confirms to the old studies because the authors themselves state nothing about it increasing total absorption rate but only that it makes the absorption more rapid, which IS a well known fact and also confirmed by the hole-in-stomach studies. There is no indication that betters the absorption though and I doubt it as there is no general principal that more rapid absorption equals greater total absorption. Then they go on to talk about probiotics and claim they increase absorption but again they dont give any evidence. They list two studies in support of the claim but if you follow it you will find only one is relevant and that one doesnt show anything like that at all. It is a study on the fattening of pigs!! and it shows that on certain probiotics the pigs get fatter. Im sure that's correct but that has about zero link to probiotics bettering protein absorption, rather the opposite if you ask me. Not surprised that some bacterial strains can make you fat though. The only time I've ever been able to add substantial weight was by eating a lot of "healthy" youghurt. Not even 5500 calories a day made me gain weight but youghurt did (gave me a belly). Just to correlate with my own experience. So again, zero indications that neither mastication or probiotics increase protein absorption given by the researchers. But of course if you eat to little protein you will have to little protein 😛
The next one seems slightly indicative of chewing affecting it but as far as I can gather from that abstract it only shows if there were undigested pieces left in the feces?? I don't know but maybe that's relevant. But they had only 16 participents and that finding was done comparing the fastest to the slowest chewers meaning it can be maximum something like 3 people involved and we don't know if the fast eaters where overweight and maybe had dysbosis and that it had nothing to do with mastication. 3 people with that many unknowns isn't too much to go on. I agree its healthy not to STRESS eating food though and if slow eating helps that, then I guess it's good. Also of course teeth are not a luxury so its not like I think chewing is unnessecary in general but I do find it to be likely to be much more important for plant foods - see the average chewing time for carnivores vs. herbivores in nature.
Next one the mastication in young women does also show zero indications of this as it doesnt even say if there was animal protein in the meal at all. Also satiation and absorption are not to be equalled, you can eat dirt to feel full (which is done in crisis situations) and it doesnt give you hardly any nutrients. So it only seems to show that when you eat slower you have time to feel full. And if you tend to overeat that can be good. I'm a fan of low stress anyway!!
Not much to add on carnivore except to repeat Im not convinced it's the high protein that helps as you dont get the same results with the same amount of meat but added carbs, meaning I think its something along the lines I already stated (I also know this personally having compared my own meat intake with some carnivores and its sometimes at the same level )
Gotta go might add something about casein later 🙂
I think most of your points are pertinent and I also hate it when a cited statement in a paper doesn't exist in the cited source or when their numbers are mixed up.
Though I won't expect to find a perfect study on mastication on the first searches, especially since most of the papers note that there is minimal research done on the effect of mastication on the absorption percentage of protein. So I wouldn't to even expect to find a high caliber study in this field to start with. It is a shame that something so truly basic as chewing and the absorption percentage of protein seem to have recievedsp little attention but there is no money in that. Chewing is free after all -if one is lucky to have great teeth for their entire life.
I hope you can use your sceptic ways to look at another study that do measure one amino acid in the blood of elder with or without serious measured chewing difficulties, it was reference The 2007 study is called:
"Postprandial whole-body protein metabolism after a meat meal is influenced by chewing efficiency in elderly subjects"
https://doi.org/10.1093/ajcn/85.5.1286
[I found the 2007 study above referenced in this paper "Chew on it: influence of oral processing behaviour on in vitro protein
digestion of chicken and soya-based vegetarian chicken", https://pubmed.ncbi.nlm.nih.gov/33645495/ (available at sci-hub].
A few quotes from the discussion part of the 2007 study:
"Postprandial increase in the leucine appearance rate was used as a surrogate of meat leucine entry rate because leucine meat was not labeled and because postprandial variations in endogenous leucine appearance rates were reported to be similar in slowly and fast digested proteins (6). However, it could underestimate meat leucine entry rate because of the transitory postprandial decrease in whole-body protein degradation but in a similar way in both groups.
Postprandial increase in the plasma amino acid concentrations observed in the present study was in agreement with data reported for young adults after a beef meat meal (22, 23, 24), with the highest concentrations being generally recorded 90–180 min after the beginning of the meal. In the present work, a close relation was observed between the variations in plasma leucine concentrations and plasma leucine entry rate."
"The amount of leucine appearing in peripheral blood during the whole postprandial period was lower in denture wearers [fake teeth wearers] than in dentate subjects (63% compared with 82% of leucine intake). This difference is surprising; we were expecting a delay in leucine appearance but not a difference in the total amount of leucine absorption. For both groups, the appearance rate returned to baseline values 2 h before the last sampling time, indicating that no more detectable amounts of dietary leucine entered the peripheral blood. Thus, the decrease in total entry rate does not seem to be attributable to an insufficiently long sampling time. It could theoretically be due to a higher inhibition of whole-body proteolysis in denture wearers than in dentate subjects. However, it seems unlikely because it was shown that postprandial inhibition of whole-body proteolysis in the elderly is not affected by the digestion rate (6). In addition, proteolysis inhibition is greater when leucinemia is higher (4, 27), which is the opposite of what is observed in denture wearers.
Thus, the lower amount of leucine appearing in plasma of denture wearers is more likely due to a higher retention of ingested leucine in splanchnic organs. Whether it is due to a longer retention of amino acids in the digestive lumen (incomplete digestion) or to a higher extraction by splanchnic tissues (digestive tract, liver) remains undetermined. A lower gastric emptying rate is likely to occur together with prolonged intestinal digestion because of fewer disrupted pieces of meat. Whether this results in a lower efficiency in the digestion of meat is unclear because an increase in transit time could compensate more or less for the differences in initial buccal disintegration of meat. Few investigators have studied the impact of chewing on digestive processes and more particularly on meat digestion. Farrell (28) observed that the degree of mastication required for maximum digestion is low and that there is no reason to suppose that full denture wearers are less capable of digesting their food. This study addressed whole-gut digestibility and did not provide information on the digestion in the small intestine, where amino acid absorption takes place. It was shown in subjects with ileostomies that beef meat proteins (from fried rump steak) have a high (94%) true ileal digestibility (29). However, swallowing of poorly disrupted boli could produce a decrease in digestion in the small intestine, as a consequence of stomach outflow of larger pieces of food, which may limit protein accessibility for digestive enzymes. This could lead to a shift in the site of meat digestion, from the small intestine to the large intestine.
A greater utilization of dietary leucine in splanchnic tissues in denture wearers than in dentate subjects also has to be considered. A high variability in splanchnic extraction of dietary leucine exists in elderly subjects; its range was 26–88% in 6 elderly men (11) and 17.5–62.6% in 14 elderly women (30). In addition, a greater splanchnic extraction was reported with slowly digested proteins when compared with fast digested proteins (6). Although in the present study the magnitude of the difference in absorption rate was much smaller than between slowly and fast digested proteins (6), the fact that denture wearers are chronically exposed to slower absorption rates may induce adaptation in the long term and lead to an increase in amino acid splanchnic extraction.
Finally, because of the delayed absorption of meat proteins and to the lower total amount of amino acids entering peripheral blood in the postprandial period, whole-body protein synthesis was lower in denture wearers than in dentate subjects (30% compared with 48% of leucine intake was used for protein synthesis during the whole postprandial period in dentate subjects and denture wearers, respectively)."
PS. Increased satiety from chewing better should be helpful for protein digestion, especially if stomach acid is as you say the most important factor, since the easiest way to lower stomach acid is to dilute it and low satiety easily leads to more snacking between meals -which would dilute the stomach acid.
What does predators do which we assumed only chew their food minimally ?
-I think those predators eat very seldomly, avoiding to dilute their stomach acid which then can become extremely acidic.
More on potential problems from excessive unabsorbed protein:
A 1997 paper called:
"Human Colonic Microbiota: Ecology, Physiology and Metabolic Potential of Intestinal Bacteria" (available at sci-hub).
http://dx.doi.org/10.1080/00365521.1997.11720708
I looked at it since it talks about the microbiome in the large intestine and how it can make some toxic compounds from unabsorbed proteins. Here are a few quotes:
"Unlike carbohydrate metabolism, many products of protein fermentation, or putrefaction, are toxic to the host. Ammonia is formed in deamination reactions, and its excretion varies markedly, with faecal concentrations ranging from 3 to 44 mM (39)."
"Amines are major products of bacterial amino acid metabolism. They are principally formed by decarboxylation of amino acids (53) and to a lesser extent by N-dealkylation reactions (54), degradation of polyamines (55) or transamination of aldehydes (56). Histamine, tyramine, piperdine, pyrrolidine, cadaverine, putrescine, 5-hydroxytryptamine and agmatine have all been identified in vivo (56). Amines produced by colonic bacteria are usually detoxified by monoamine and diamine oxidases in the gut mucosa and liver, but in some circumstances these substances can enter the general circulation, with severe physiological consequences for the host (57). Although the physiological significance of large intestinal amine formation in healthy individuals needs to be established, many studies indicate that it may potentially have harmful effects in the long term, since amines serve as precursors in nitrosamine formation (58). N- Nitrosation reactions in the large intestine are dependent on pH, as well as the availability of nitrite and amines, and many intestinal bacteria have the capacity to form N-nitroso compounds from secondary amines (59), which can be detected in faeces ( 60).
Amine formation in the large bowel may affect the host in other ways. Like other low molecular weight species, these metabolites are probably rapidly absorbed from the gut lumen (61). Amines have been associated with migraine (62) and the onset of hypertensive symptoms (63), while in patients with liver disease, amines formed by colonic bacteria can induce hepatic coma (57). It has also been reported that N-acyl and acetoxy derivatives of putrescine and cadaverine produced by intestinal bacteria are elevated in the blood of schizophrenics, and that colon cancer patients excrete higher levels of these substances than healthy individuals (64). Amines are pharmacologically active in other ways, in that some, including tyramine, histamine, cadaverine and putrescine, act as pressor or depressor substances, and may act as stimulators of gastric secretion or as vasodilators (56)."
Ok, I don't know how much I have to add but at least a couple of things would be possible to clarify. On the usefullness of dead bacteria I can attest to that. It's at least one know factor leading to this, namely that the cell-membranes of the dead lacotbacilli has anti-inflamatory properties. This would reduce gut serotonin and better intestinal wall integrity as well as facilitate healthy uptake of nutrients including protein . I have great doubts about enzymes having an effect if the bacteria is already dead as they would have to be produced by the metabolism of the bacteria. I am also not agreeing that it's so hard to change the bacteria with the diet. There was a study some years ago on a huge number of people across the globe classifying modern bioms into three main groups, each signified by the predominance of certain strains of bacteria - these again pretty accurately reflected the eating habits of the people having these microbioms and being sorted in to three groups of low meat, high meat, and high vegetable oil diets. So if it's such a good correlation between diet and and biom it's not likely that the diet doesn't affect it. Of course other factors are important too - everything from what you pick up in the birthcanal during birth to how your hygiene is. Also medicine and hormones and polutants- and I assume vitamin A - affects this biom - makeup. So what' most difficult isn't changing it but making people change their habits. Not saying that its such and easy thing of course it can be a challenge and I don't know if all people in all circumstances can if there ever was such a thing. I do think that the idea that people had more uniform gutbioms earlier i highly unlikely though. The modern gut-biom is largely identifyable by it's lack of diversity - which is also why it was possible to gorup the bioms into three main classes. The few more "primitive" cultures left are not identical in their biom and are mainly carachterized by the diversity of species of bacteria including spores in their gut. It would be a far stretch to imagine a siberian hunter an a african tropical dweller to have the same diet or biom. Also it tends to be group consistent. Meaning you get very similar bioms to people you live with - this is even observable in modern hygenic households. So each tribe would probably overlap and most would have a diverse biom, but that would vary greatly according to people climate and diet around the world. Which is consistent with what we find today and also makes sense as the bacteria eat different stuff and have to eat what the host gives them. Disease and not changing their lifestyle is what makes us not change gut-biom. You are right the most research have been done on lactobacilli. its interesting because as the name indicates it mainly thrives in people eating dairy. And traditionally noone did and the hunter-gatherers with diverse gut-bioms hardly have them. They also tend to colonize the gut so that they outcompete other species as I mentioned and this tends to make it's own problems long term. So you have to keep taking them and also makes you more vulnerable. Most "primitive" (I guess all) societies have aswfull/non-existing hygiene and eat things that we wouldnt touch including dirt raw food and feces-particles. The french where some of the first to investigate pro-biotics (or rather spore-biotics) as they learned from the beduins (don't remember might have been the berbers actually) that they could avoid the deadly gut-infections/diarias that their soldiers suffered from by eating camel-dung. This was later extracted and refined into the worlds first spore-biotic (its still in sale). I think maybe it would be hard to replicate such a biom in a modern setting. Maybe that kind of biom is only healthy if you yourself are healthy. It usually contains a lot of doubious stuff like e-coli and several acutley toxic spores but they are seemingly doing fine with it due to the body having the resources to handle it. I guess it's like its good to have wild dogs to ward of predators and enemies if you are strong and can keep them in check. If not they attack you instead?? this I have absolutly no research behind but Im myself sceptical of supplementing these broadspectrum and spore-biotics as it sometimes observably going really wrong. Like out of 100 people getting better or neutral there is also one dying from it. (fictious numbers but there is a reason why there is a hesitancy about those - lactobacilly don't do that). Now that was a long bacterial rant. I also think where in the gut the bacteria are is an important factor. Lots of problems comes from the bacteria being in the wrong part of the intestine and fermentation happening due to all kinds of digestive problems that might not be bacterial in origin but worsend by them. like with SIBO. Btw if you want to have the anti-inflamatory effect of lactobacilli without the chance of them overpopulating your intestine you can buy a regular one, empty the powder infront of a strong UV light (the sun for several hours or a tanning bed for about 10 min). this will kill the bacteria but keep them intact. So when you eat it you get the effect without changing the biom. On the liverfailure type I am still a bit out of my field. I mean not all kind of liver problems calls for low liver according to standarized medicine either. I don't know much about that though. But on the kempner diet being horrible for kidneys that sounds veeeery strange as just low protein is what is the standard for managing kidney problems and was used successfully for that for over 70 years. how do you reach that conclusion (for the record I still don't recommend it as a diet but it seems to work very well a a last resort or something).
Quote from David on May 19, 2023, 10:09 pmI think most of your points are pertinent and I also hate it when a cited statement in a paper doesn't exist in the cited source or when their numbers are mixed up.
Though I won't expect to find a perfect study on mastication on the first searches, especially since most of the papers note that there is minimal research done on the effect of mastication on the absorption percentage of protein. So I wouldn't to even expect to find a high caliber study in this field to start with. It is a shame that something so truly basic as chewing and the absorption percentage of protein seem to have recievedsp little attention but there is no money in that. Chewing is free after all -if one is lucky to have great teeth for their entire life.
I hope you can use your sceptic ways to look at another study that do measure one amino acid in the blood of elder with or without serious measured chewing difficulties, it was reference The 2007 study is called:
"Postprandial whole-body protein metabolism after a meat meal is influenced by chewing efficiency in elderly subjects"
https://doi.org/10.1093/ajcn/85.5.1286[I found the 2007 study above referenced in this paper "Chew on it: influence of oral processing behaviour on in vitro protein
digestion of chicken and soya-based vegetarian chicken", https://pubmed.ncbi.nlm.nih.gov/33645495/ (available at sci-hub].A few quotes from the discussion part of the 2007 study:
"Postprandial increase in the leucine appearance rate was used as a surrogate of meat leucine entry rate because leucine meat was not labeled and because postprandial variations in endogenous leucine appearance rates were reported to be similar in slowly and fast digested proteins (6). However, it could underestimate meat leucine entry rate because of the transitory postprandial decrease in whole-body protein degradation but in a similar way in both groups.
Postprandial increase in the plasma amino acid concentrations observed in the present study was in agreement with data reported for young adults after a beef meat meal (22, 23, 24), with the highest concentrations being generally recorded 90–180 min after the beginning of the meal. In the present work, a close relation was observed between the variations in plasma leucine concentrations and plasma leucine entry rate."
"The amount of leucine appearing in peripheral blood during the whole postprandial period was lower in denture wearers [fake teeth wearers] than in dentate subjects (63% compared with 82% of leucine intake). This difference is surprising; we were expecting a delay in leucine appearance but not a difference in the total amount of leucine absorption. For both groups, the appearance rate returned to baseline values 2 h before the last sampling time, indicating that no more detectable amounts of dietary leucine entered the peripheral blood. Thus, the decrease in total entry rate does not seem to be attributable to an insufficiently long sampling time. It could theoretically be due to a higher inhibition of whole-body proteolysis in denture wearers than in dentate subjects. However, it seems unlikely because it was shown that postprandial inhibition of whole-body proteolysis in the elderly is not affected by the digestion rate (6). In addition, proteolysis inhibition is greater when leucinemia is higher (4, 27), which is the opposite of what is observed in denture wearers.
Thus, the lower amount of leucine appearing in plasma of denture wearers is more likely due to a higher retention of ingested leucine in splanchnic organs. Whether it is due to a longer retention of amino acids in the digestive lumen (incomplete digestion) or to a higher extraction by splanchnic tissues (digestive tract, liver) remains undetermined. A lower gastric emptying rate is likely to occur together with prolonged intestinal digestion because of fewer disrupted pieces of meat. Whether this results in a lower efficiency in the digestion of meat is unclear because an increase in transit time could compensate more or less for the differences in initial buccal disintegration of meat. Few investigators have studied the impact of chewing on digestive processes and more particularly on meat digestion. Farrell (28) observed that the degree of mastication required for maximum digestion is low and that there is no reason to suppose that full denture wearers are less capable of digesting their food. This study addressed whole-gut digestibility and did not provide information on the digestion in the small intestine, where amino acid absorption takes place. It was shown in subjects with ileostomies that beef meat proteins (from fried rump steak) have a high (94%) true ileal digestibility (29). However, swallowing of poorly disrupted boli could produce a decrease in digestion in the small intestine, as a consequence of stomach outflow of larger pieces of food, which may limit protein accessibility for digestive enzymes. This could lead to a shift in the site of meat digestion, from the small intestine to the large intestine.
A greater utilization of dietary leucine in splanchnic tissues in denture wearers than in dentate subjects also has to be considered. A high variability in splanchnic extraction of dietary leucine exists in elderly subjects; its range was 26–88% in 6 elderly men (11) and 17.5–62.6% in 14 elderly women (30). In addition, a greater splanchnic extraction was reported with slowly digested proteins when compared with fast digested proteins (6). Although in the present study the magnitude of the difference in absorption rate was much smaller than between slowly and fast digested proteins (6), the fact that denture wearers are chronically exposed to slower absorption rates may induce adaptation in the long term and lead to an increase in amino acid splanchnic extraction.
Finally, because of the delayed absorption of meat proteins and to the lower total amount of amino acids entering peripheral blood in the postprandial period, whole-body protein synthesis was lower in denture wearers than in dentate subjects (30% compared with 48% of leucine intake was used for protein synthesis during the whole postprandial period in dentate subjects and denture wearers, respectively)."
PS. Increased satiety from chewing better should be helpful for protein digestion, especially if stomach acid is as you say the most important factor, since the easiest way to lower stomach acid is to dilute it and low satiety easily leads to more snacking between meals -which would dilute the stomach acid.
What does predators do which we assumed only chew their food minimally ?
-I think those predators eat very seldomly, avoiding to dilute their stomach acid which then can become extremely acidic.
Thanks for the confidence. I think that is a much better study. So it might be that it is an indication of chewing helping- its not like completly unreasonable or anything - but also it might not. I think they discuss the problems with it quite well in the quotes you give from it. As they note that it wasn't randomized if people chewed well or not but based on if they had teeth/dental implants/prothesis. The people not having proper teeth would then presumably also not eat so much meat on a day to day basis (as was stated in the korean study) and thus have a different and less effective micro-biom. or possibly other nutrient deficiancies. To be fair I might seem to be contradicting myself here as I claimed that its not easy to see that the enzymes or gutbiom helps. But it helps from a general health perspective indirectly and also surely worse health would mean less uptake normally. I end up thinking about transit time actually which is largely determined by thyroid-hormone levels. It possible that the regular meat eaters just have better working thyroids. Im not formulating myself well here. to much thinking 😛 But metabolic status is affected by both undereating and protein status so the normal observation that people with bad teeth eat less would cause lower metabolism and poorer absorption. So what we do see is that people with teeth that eat meat regularly absorb protein better. I end up thinking its very hard to guess if the chewing affects it again. It would be doable without a giant setup if you took only people with bad teeth and gave half of them a prosthetic just for the experiment as well as checked their general health markers and metabolic status before the experiment. It would only be an extra blood-sample some temps and a few prostthetics and you would have had more reliable answers. The chicken soy study I've already commented on. Im not sure what to make of the last one but maybe Im just too tired now. But I don't doubt that both too much and too little protein causes problems and maldigeston surely does. The reasons and the cure is the enigma 🙂
I hope there will be a study that can say more definitively if chewing affects the absorbtion percentage of protein. Your idea of having some type of denture that makes chewing worse for normal people would be interesting. Though if they can find test subjects that already eats very fast with minimal chewing they could use that as baseline and then compare it to when they have to chew each bite for a much longer time before swallowing.
I don't have a fixed view on how stable the gut microbiome might be in a perfect world and under perfect circumstances. I don't think anyone can know exactly any way. What I think is that you can change some part of the gut microbiome significantly with diet and habits but that I believe the main part is probably quite static. I don't even think scientists could effectively grow anaerobic bacteria (the most important gut bacteria) from humans until something like the 1930s-1950, which is not too long ago.
I attach a table from a 1971 doctor's thesis on specifically the gut microbiome that you might find interesting. The attached table shows the measured gut microbiome from people living in: England, England (vegans), Uganda, USA (white) and Japan.
The 1971 doctor's thesis is called:
"Factors influencing the human intestinal flora" by John Crowther.
http://hdl.handle.net/10044/1/16306
Anyhow I think focusing on proper chewing is a form of Pascal's wager: there is no apparent downside besides having to take a little more time for eating while at the same time having the potential for a great upside in digestion.
https://en.m.wikipedia.org/wiki/Pascal%27s_wager
PS. Chewing well if someone is trying to lose weight is certainly helpful to reduce the risk for overeating. It takes some time for satiety to kick in.
PSS. On the Kempner diet I think the same thing as the original posted 1961 paper applies, that too much protein for a person is tough in the body. As that 1961 paper said, during an acute sickness phase like highly elevated ammonia in the blood, it is best practice (safest) to lower protein and then slowly increase it once the worst part has passed.
-Though let us not forget that Kempner is known to have wipped people to make them compliant to his diet. That might explain why Kempner diet seems mostly forgotten and I don't know if he has any following of his diet in present time?
EDIT: Regarding the attached table, there can still exist huge variations within each of the main bacterial and fungal families, there are after all legions of different bacterial and fungal strains.
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A 1971 paper proposing that enough protein is helpful for carotenoids. See the attached figure from the paper talking about the proposed serum protein sponge which might be Retinol Binding Protein-4 (RBP-4). Which I think once again points towards absorbing enough protein, without excess fermentation, to be critical for a smooth detox.
"Golden Ovaries" by S. W. Page [1971]
https://doi.org/10.1111/j.1479-828X.1971.tb00447.x
(available at sci-hub)
Abstract:
"This report concerns 6 women who presented with an excessive intake of carotene-containing foodstuffs and menstrual disturbance. Four of these were well nourished with respect to protein intake, while the other 2 were undernourished (anorexia nervosa type syndrome).
Four of the patients were in an older age group (range 35-58) with excessive or irregular vaginal bleeding; 2 of the patients were younger (22, 23) and presented with oligo-amenorrhoea. The ovaries in all patients were golden yellow in colour and possessed a characteristic histological appearance. Fat stains revealed abundant, highly-dispersed, lipid granules occurring throughout the ovarian cortex, not restricted to areas around the corpora lutea; special stains for carotenoid pigments were strongly positive, the latter giving the ovary its uniformly yellow colour, which is usually only seen in relation to the corpus luteum.
It is proposed that those women with a normal protein and a high carotene intake suffered from a hypervitaminosis A syndrome leading to a bleeding tendency. Those women with a sub-normal protein intake may have had a suboptimal conversion of carotene to vitamin A and no bleeding tendency."
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golden ovaries!