Neu5Gc and red meat

Commented on July 01, 2015
Created January 05, 2015 at 9:36 AM

Some studies are now saying that the Neu5Gc in red meat may cause cancer, whats your take on this? If this is so then how come traditional societies didnt seem to get cancer from eating meat?

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3 Answers



on January 05, 2015
at 12:28 PM

"Long-term exposure to this sugar in mice caused a five-fold increase in their chances of developing cancer."


Are mice carnivores?  Are mice humans?  What was the original chance of said mice to develop cancer? 1 in 10? 1 in 100? 1 in 100,000?  5x 0 is still 0, right?

"Humans cannot synthesize Neu5Gc because the human gene CMAH is irreversibly mutated, though it is found in apes."

Ok, so if it's found in apes, does this molecule give apes cancer?  No?  Why would it give humans cancer?  Does taking other human antibodies and injecting them in mice cause adverse reactions to the mice that would normally not occur in nature?


Does this molecule even make it past digestion undamaged?  Do our gut flora digest this molecule?  Are there other compounds in meat that would prevent this molecule from causing or encouraging cancer growth?


"Neu5Gc is rapidly absorbed in the intestinal tract, some of which is converted to acylmannosamines by intestinal cells and bacteria, and reconverted back to Neu5Gc in the body. According to an absorption study, about 3–6% of the ingested dose of Neu5Gc was excreted within 4–6 hours, with the peak excretion rate at 2–3 h and a return to baseline levels within 24 h."  So, basically it would also depend on what kind of gut flora you have.

Looking at the supporting materials found here: http://www.pnas.org/content/suppl/2014/12/26/1417508112.DCSupplemental

It looks to me like Cheddar Cheese has a far larger quantity of this acid, and yet, that's not mentioned anywhere.  Why are the authors of this article and the media biased against red meat, but failed to mention that cheddar has an order of magnitude larger contents of this molecule?  Something smells like a political agenda here!  (see table S3, Bison has 586, cheddar has 5700! Wild caught salmon has 1488, tilapia 1849,  mahi-mahi has 1615, whitefish caviar 7400, salmon caviar 3501 pmol/mg).


So why are all these articles against eating meat when they should be against eating fish, caviar, and cheddar?  Hmmm???



"Neu5Gc is still reported to be found in concentrated in human cancers, as well as found in fetal samples, suggesting a dietary source." Big deal, cancers like eating sugars, this is a sugar molecule.  Why not an article saying "Sugar causes cancer to grow?"


And a very interesting snippet:

"Disclosure: Ajit Varki and Nissi Varki are co-founders and have equity interest in SiaMab Therapeutics, Inc., a biotech company with an interest in Neu5Gc and anti-Neu5Gc antibodies."





on July 01, 2015
at 05:05 AM

"Neu5Gc is still reported to be found in concentrated in human cancers, as well as found in fetal samples, suggesting a dietary source." Big deal, cancers like eating sugars, this is a sugar molecule. Why not an article saying "Sugar causes cancer to grow?"


Oh, on this note-  the question isn't if the cell is consuming the sugar for energy, it is if it is expressing it on the cell membrane.  The reason it "suggests a dietary source" is that humans can't make it (but your dog can, a cow can, a chicken cannot, a shrimp cannot).  Finding a sugar that isn't being metabolized or created by the cell is certainly interesting- it would provide a reason for the immune system to have an issue with it in the first place, for instance, etc.  



on July 01, 2015
at 04:50 AM

"Are mice carnivores? Are mice humans? "

Irrelevant.  The mice were explicitly modified to be LIKE humans in one way- they no longer produced the Neu5Gc.  The precursor, Neu5Ac, is the only one humans have.  The whole point is that they are trying to test the theory that lacking Neu5Gc, as humans, birds, many fish, but no OTHER mammals, leads to development of antibodies to this sugar (this part is known- they can test for these antibodies, and almost all humans have them, it is why serum sickness happens)... and further, that these antibodies cause inflammation in some people, and can cause problems.  


The biggest problem in your analysis- and it's big enough that you should edit your post, if that's possible here, and big enough that I actually made an account just to scold you-  is that you say:


"Bison has 586, cheddar has 5700!"


No.  That's not true.


The first column you linked is Neu5Ac.  This is the one that all animals have, including humans.  It's not the important one.  In fact, if this inflammation theory is true, you'd probably want to seek out food sources with MORE of this one, while avoiding the Neu5Gc one.  I get that they are one letter off and it's an honest mistake, but you are really going to confuse anyone who reads it.  

The chart says Bison have 293 pmol/mg bound (presumed to be not available for use) and 22 pmol/mg free (and presumably able to incite immune response).  Cheddar would have 104 pmol/mg bound (around a third of bison) and 2 pmol/mg free (around a tenth of the bison).


The important data columns for looking at Neu5Gc are the third through sixth and final. 


Here's Neu5Ac's name on wikipedia:


And here's Neu5Gc (which you also linked to):




I do agree that the angle of this is going to be "don't eat meat".  I've been googling the heck out of this, and many articles downplay (and veg* commenters totally are hostile about) the fact that there are plenty of meats that don't have much or any Neu5Gc.


Remember, there's a ton of genes that make people act a ton of different ways in food, and that's before you get to stuff we don't understand well, like gut bacteria.  It's entirely possible that red meat is terrible for you and great for someone else, or vice versa.  Because the mechanism being discussed involves immune response, how much of that type of immune cell and how well your body deals with inflammation are probably all important things as well.  Most studies (and diets) normally pretend that everyone is mostly the same, but we just understand so little...  


As to the caviar point, they probably don't make that point because caviar is not that commonly consumed.  But it's a pretty important detail, and you are right to point it out- the fact that it is all "bound" may or may not be relevant.  


I think this study is stupendously interesting.  This might explain why some people have serious issues with meat and others are veritable shining gods- if it's about immune response and inflammation, people could have very different responses to that, and you could even test for that.  


For me, I'm actually going to try to absolutely avoid the Neu5Gc for a couple months- if that makes a difference in anything I can detect, then great.  Otherwise, it'll be back to delicious and red meats.



on January 05, 2015
at 09:55 PM

Interesting point about the cheese being high in Neu5Gc, seems like the media wants to scare people from eating red meat because cheese is more civilised whereas red meat is not.


on January 07, 2015
at 03:22 PM

Isolating a single chemical from a food and administering it in extremely large doses to genetically engineered mice in order to blame said food for the deaths of millions of human lives from cancer? 

Where do these researchers get their funding from, PETA? Lol. What a joke.



on January 05, 2015
at 12:06 PM

Because Neu5Gc doesn't cause cancer (although consumption correlates with cancer in modern diets). It correlates because meat-eating diets generally are poorer than non-meat eating diets in terms of quality. 



on July 01, 2015
at 05:03 AM

The entire point of the study was to make mice that have antibodies against Neu5Gc, just as humans do, and then see if they had some negative effects.  They did.  That doesn't prove anything, but it really points in an interesting direction- specifically that the immune response might cause inflammation, which could then cause damage in *some* people (all people have the immune response, but it's probably just whatever in many).  

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