Spartian, still waiting here.
Anyone else having research on the topic on hand? I have found it pretty hard to find proof that cooking meat increases digestibility and yet you all seem to present it as a fact. I havent, admittedly looked that hard though…
[quote]Mikael LS wrote:
Spartian, still waiting here.
Anyone else having research on the topic on hand? I have found it pretty hard to find proof that cooking meat increases digestibility and yet you all seem to present it as a fact. I havent, admittedly looked that hard though… [/quote]
Unless there’s a typo in your post, I think we agree. Cooking meat does not increase digestibility.
There isnt - to my surprise, cooking seems to decrease digestibility. Neither you or the opposite camp have however presented either way yet, and since i myself am busy at the moment, i was hoping that someone could present some research.
[quote]Mikael LS wrote:
There isnt - to my surprise, cooking seems to decrease digestibility. Neither you or the opposite camp have however presented either way yet, and since i myself am busy at the moment, i was hoping that someone could present some research.[/quote]
What exactly do you mean by digestability in this sense? I was initially thinking bioavailability, but this post makes me think that your operationalization may be more salient in nature.
Gas production? Bloat? Speed of transit?
i suggest anyone who thinks this thread is interesting or relevant start eating raw chicken every day, and report back their findings in a year. how bored must I be tonight to engage in this?
Im thinking absorbtion of amino acids. I have come across a few papers stating that the effeciency of the digestive enzymes is hampered after heat treatment because of carbonylation of the side chains, aggregation and stuff like that. There is a little more to the story than that, but I would rather go eat, as i am going to bodybuild excessively tomorrow, and so I will let everyone who have boldly stated that cooking increases digestability, present their sources.
No-one needs to worry about this as an issue.
[quote]Mikael LS wrote:
Im thinking absorbtion of amino acids. I have come across a few papers stating that the effeciency of the digestive enzymes is hampered after heat treatment because of carbonylation of the side chains, aggregation and stuff like that. [/quote]
Dude, if the enzymes that digested protein existed in the chicken itself, which is getting cooked, then the chicken would be getting digested before being eaten.
I don’t think mother nature is stupid enough to put chymotrypsin and proteases IN an animals muscle tissues in quantities that would be significant (maybe enough to induce protein turnover, not enough to significantly play a role in digestion)
Plus, if they exist at a muscle tissue’s pH, then they would be denatured at the stomach’s pH, I don’t know of any enzymes which can function or survive at such a wide variance.
Hydra, sorry, I am being unclear. What I mean is that heat treatment of meat decreases the effeciency of digestive enzymes (that have not been heat treated) in conditions mimicking the digestive process.
Im not a raw food idiot, dont worry! In fact I recently published an article bashing those people back home.
Now, in fear of repeating myself, will someone please present som research? I have so far had only a look on Sante-Lhoutellier 2008 and Gatellier 2008 (and Schroeder 1960, lol) and they conclude that cooking decreases amino acid liberation using microreactors simulating the digestive tract. Again, if the fact is that cooking meat increases digestibility, no problems should be had by digging up the appropriate research?
Plateu: I am grateful for your input. Could you please elaborate on what is and what is not accepteble to discuss in your opinion?
“I had someone tell me last night that chicken is UNHEALTHY because if it’s cooked to the point where its HEALTHY…”
Huh?
Studies posted by Mikael LS and Opposing View
SANTE-LHOUTELLIER et al. 2008
J. Agric. Food Chem. 2008, 56, 1488-1494
Effect of Meat Cooking on Physicochemical State and in Vitro Digestibility of Myofibrillar Proteins
shows clearly:
my comments:
Cooking temperatures are lower than that used commonly in contemporary settings (edit - this is incorrect). The high temperature treated meat had interesting response pattern compared to the other cooked meats. This combined with contradictory results and it being a simplified benchtop model limit the amount of data that can be extrapolated to humans.
Gatellier et al. 2009
Meat Science 81 (2009) 405-409
Digestion study of proteins from cooked meat using an enzymatic microreactor
my notes:
This is a souped up version of part of the above experiment. It doesn’t say anything about the body’s ability to uptake the digestion products of cooked protein. It shows some effects on digestion in the reactor they created to replicate the stomach. The usefulness of their apparatus or a similar one could be set up to test peptides produced which could be very important in food allergen testing, but applicability to humans is limited at best.
Boback et al. 2007
Comp Biochem Physiol A Mol Integr Physiol. 2007 Nov;148(3):651-6
Cooking and grinding reduces the cost of meat digestion
free PDF:
http://pdfcast.org/pdf/cooking-and-grinding-reduces-the-cost-of-meat-digestion
This is a study done on snakes (humans have about 25% the metabolic response, so differences will be much smaller) that shows decrease in energy required to digest meat due to both grinding and cooking, and the additive effects of the two processes.
There is nothing in the conclusions about amino acid liberation. In fact the first study doesn’t even have a conclusion (results and discussion section) and the conclusion of the second study is that the contraption may be used for “pre-screening experiments prior to in vivo studies”, that it was better than the test set up in the first experiment, and they are building a new better, automated system.
I understand how the results can appear to support the notion that cooking decreases protein digestion. However, no attempt is made to measure digestion or uptake because it is in vitro.
The third study shows that there seems to be a benefit to cooking. The authors conclude this and discuss implications to humans and studies done relating to this (could be good reading).
Peter: Thank you, your comments are useful. I do not agree with point 4 regarding the Sante-Lhoutellier study; none of the treatment are significantly different to the control even though they must have done something funny with the ANOVA, because 5 minutes looks pretty significantly increased to me. 15 minutes is clearly not, and 15 and 30 and 45 are, if anythin inhibited. Also, i disagree that the temperature used is lower than in contemporary settings. In fact, only rarely will you have meat at a 100 degrees C when cooking (the core temperature will usually be in the 60-ish range, as this is when the meat coagulates and changes color). This is actually something that speaks againts the usefulness of this study.
As a whole, i agree with your thoughts on the Gatellier study.
I do however find it far fetched to conclude that cooking does not negatively affect protein digestion based on those two studies. I agree that the studies do not necessarily apply to humans, but that is very far from concluding that cooking increases digestion. If anything, the opposite apply (based on those two, at least). Prolonged treatment at 100C or beyond WILL cause amino acid carbonylation and aggregation, and this simply changes the substrate and hence the digestive enzymes’ specificity towards them.
The snake study on the other hand is very interesting. This one I can accept. I will interject that collagenous tissue is different from myofibrilar, rats are not humans and that cooking temperature was lower (and heat treatment likely shortened, since it does not take long to heat 150g of beef to 80C in a microwave), but still, it is more applicable than the reactor studies.
Here’s an older study I came across called Mechanisms of Heat Damage in Proteins:
“It can be concluded that cross-linkages are formed in proteins during severe heat
treatment, and it seems likely that they reduce the rate of protein digestion, possibly by
preventing enzyme penetration, or by masking the sites of enzyme attack.”
That being said, they cooked the protein at autoclave temperatures (121 Celsius) for extremely long periods of time (upwards of 8 hours) so it seems dubious that this would be relevant to cooking chicken for human consumption.
Let’s start with point 4 I made about Sante-Lhoutellier 2008
Looking at the diagram (see next post), there is most certainly a significant difference. I could care less about the ANOVA. The authors even point out that there is a 2-fold increase in proteolysis. I am certain that if they repeated the study with a higher number points in between the results would be statistically significant. As we both point out, the two shorter cooking times exhibit much higher rates, and getting significantly less with increased cooking time to the point of a decrease. This is also noted in the discussion by the authors.
I was outright incorrect about the cooking temperatures being lower, they are in fact higher as you point out. Meat is considered cooked when internal temperature reaches 60-75 Celcius (140-170 Fahrenheit), in this study they reached that point in about 4 minutes based on the graph for the 30 minute group. The high temperature one actually reached 170 Celcius but was only at this temperature briefly.
It may be better to characterize this as cooking normally leads to increased proteolysis in the intestines and decreased in the stomach, but overcooking eliminates those gains and thensome if left longer. This is mentioned in a link found through the Gatellier et al. 2009 study:
Clifford, W. M. : Biochem. Jour., 1930, xxiv., 1728. as reported in The Lancet, Feb. 21, 1931, 422.
The gist is that there are favourable benefits of lightly cooked (brown through) meat and that overcooking (boiling for hour) removed said benefit. Also, heating up normally cooked meat does not destroy its digestibility.
The importance of pepsin proteolysis is chiefly for uncooked food so it can proceed to the intestine for further proteolysis by the pancreatic enzymes. This is the important step in digestion of protein from a perspective of amino acid uptake potential. And the rate seems to be twice as high. This must more than make up for the decreased pepsin proteolysis rate as evidenced by the results of the python study and other similar ones it cited.
As for the collagen, the author may have been mistaken, careless or whatnot, the temperature for myofibils is around 10 Celcius lower, or maybe collagen was picked because it required the highest temperature.
So on further analysis, it seems that the pancreatic enzyme data actually support the notion that cooking meat has benefits. I have a bunch of abstracts that I am tracking down full texts for with more pertinent info.
If anything good comes up, I will post it, but I think at this point the matter of pepsin digestion is explained by the body’s response to uncooked versus cooked meat as all types of cooking resulted in similar changes in protein structure and proteolysis by pepsin. Further, reasonable cooking seems to induce increased pancreatic digestion.
Here is the graph in question from Sante-Lhoutellier 2008
Good upsummation. I have no comments to your post, other than the fact that the study you cite is, you know, 80 years old. The methodology does appear solid in my opinon, though.
I have howeever notitced a strong tendency: It seems that in the studies where meat is overly cooked - say, kept above 100C for extended periods - the digestability goes down. When it is only sufficiently cooked, digestibility goes up. This is in perfect agreement with the molecular observations where carbonyl formation, protein aggregation and whatnot is seen at the extended periods of cooking I just mentioned.
I will conclude that reasonable cooking is good for the digestibility of meat, causing better uptake of amino acids, less energy expended in digestion and fewer carcinogenic microbial products formed in the colon. Does anyone disagree or have anything to add?
[quote]thaiclinch wrote:
What’s up fellow T members?
I had someone tell me last night that chicken is unhealthy because if it’s cooked to the point where its healthy to eat it looses its nutritional value due to the high temp at which its cooked…
I have been researching it all day trying to find something about this because I believe 100% its false information that they are regurgitating out of there face. Has anyone ever read or heard anything similar to this??
Thanks and sorry for the stupid question. [/quote]
You’re answer to this person should have been: “Cool story, bro”
That would have saved some bandwidth.
But apparently, there is plenty of bandwidth for you to play captain obvious on the internet…?
I find your attitude more than strange seeing as we are on a forum devoted to debating nutrition. You might be one of these staunch supporters of keeping myths alive?
Nerds. All of you.