Written by: Kevin Cann
I am sure seeing this headline on the Paleo Solution blog caught your attention. That title was the title of a January 2, 2015 article published in Discover magazine. If you live in a cave and have not yet been inundated with this via your Facebook newsfeed check it out first, http://blogs.discovermagazine.com/d-brief/2015/01/02/red-meat-cancer-immune/ , and here is a copy to the research, http://www.pnas.org/content/early/2014/12/25/1417508112 . Typically I do not get into these debates anymore as it is just the same old arguments. However, this study mentioned something a bit different. These researchers are blaming a sugar molecule, Neu5Gc, found in beef, lamb, and pork.
Their argument is that the human body cannot digest this sugar molecule and this causes an inflammation response. Neu5Gc cannot be synthesized in humans due to an irreversible mutation of gene CMAH. This gene is actually found in other mammals including apes. Neu5Gc is immunogenic in humans and DOES cause an inflammation response. (http://www.ncbi.nlm.nih.gov/gene/8418 ).
Researchers, just like anyone else, want to get their names out there. Showing the dangers of red meat has always had some media sex appeal. Science has already known that Neu5Gc causes an immune response in humans, so why would researchers need to do further research on mice? My guess would be to get their names published in a magazine.
These researchers knocked out the CMAH gene in the mice to “humanize” them. They then fed them the mouse equivalent of red meat. This was mouse chow enriched with the Neu5Gc. They then fed the mice this for the next 12 weeks. The mice were then injected with the antibodies for Neu5Gc to mimic the human response. The mice fed the enriched chow were 5 times more likely to develop tumors then the mice fed a normal diet.
The mice in this study tended to develop tumors mostly in the liver. However, the popular claim against red meat is colon cancer. The fact that the mice were developing tumors in different areas brings to question the difference in the digestion of the sugar molecule between the two species. Knocking out certain genes in mice is good for metabolic research, but for cancer research it gets a bit dodgy. Humans and mice will disburse Neu5Gc throughout their tissues in different ways. This may explain why the mice were developing liver cancer and the suspected outcome would have been colon cancer. Also, the fact that the mice were developing liver cancer makes me question the dosages they were receiving. Our liver is our major detox organ and if the dosage of a “poison” was superiorly high, this could be the cause of the liver cancer. Remember the poison is in the dose.
All foods contain at least one compound that can lead to negative health outcomes when taken at extreme doses. However, none of these compounds tend to show these same negative health outcomes when taken in the amount found in a normal dietary setting. If I am a researcher and I want my research published in magazines this is exactly how I would do it. I would overwhelm a mouse with an amount of one of these compounds that is larger than any human would ingest on a given day, slap a catchy title on it like “Red Meat Causes Cancer” and send it out for everyone to read. The layperson is none the wiser and my name is published in major media outlets. Not saying that this is what happened, but definitely something to keep in mind.
Research has shown using the same mouse model that Neu5Gc is present in cancerous cells. However, just because the sugar molecule is there does not mean that it is the cause of the tumor. We know that some tumors require sugar for the energy to continuously divide. Perhaps Neu5Gc is one of the sugars it can utilize as fuel. This would make sense from an evolutionary perspective since humans do not synthesize the sugar.
After quite a bit of digging I was able to find that the dosages that they gave the mice in the study were about 100 times higher than the dosages that humans consume when we look at how much Neu5Gc was consumed per kg of bodyweight. Also, 12 weeks is about half of the lifespan of the mice they used in the research. To sum it up these mice were fed 100 times more of the sugar molecule then humans would consume per day for half of their lives. To add even more, this was not within the context of their normal diets.
My question would be, what would happen if we consumed normal amounts of Neu5GC within the context of a normal diet consisting of fruits, vegetables, nuts, seeds, and healthy fats? I have written about the meat and inflammation link in past articles (http://robbwolf.com/2013/12/26/meat-leads-inflammation/ ). Meat is an important source of many critical nutrients including our B vitamins and iron. If the sugar molecule Neu5Gc is toxic to humans within the context of a realistic diet we should expect to see increased cancer rates amongst populations that consume high meat diets. These increased cancer rates should correlate directly with the amount of meat consumed as well. However, this is not what we see.
There are a few hunter gatherer groups that can be found across the planet. One of them being the Maasai eat a high fat diet from animal products, but yet do not suffer the same lifestyle diseases that are so abundant in the Western hemisphere (http://sciencenordic.com/maasai-keep-healthy-despite-high-fat-diet ). Two other groups that are compared often are the Mormons and the Seventh-day Adventists. The Mormons eat meat and the Seventh-day Adventists do not. Other lifestyle factors between the two groups are very similar. Their smoking rates are lower, they have strong spiritual connections, and they drink less. Their total life expectancies are comparable at 2-4 years higher than the general population. They also both have cancer rates much lower than the general population. This includes colon cancer, a cancer in which red meat is supposed to negatively affect (http://www.ncbi.nlm.nih.gov/pubmed/1449267 ).
I am going to go out on a limb here and say that Neu5Gc is not a major cause of cancer. It comes down to a plethora of lifestyle behaviors. The more positive actions we take to take care of our health the better off we will be. Manage your stress, move around a bit, get some sunlight, hug your mom, and eat some steak.
For more information on this checkout the podcast with guest Chris Kresser: