Steak raises cancer risk and now we know why
Some of you may remember a recent study showing why red meat is bad for the heart, while now there is a study showing why steak — or in particular red meats — raise the risk of cancer. To be clear, I am still very much a red meat eater and this is no way intended to change anyones opinions on steak consumption, but it is nice to understand the science behind what we put in our mouths.
It has been known that people who eat a lot of red meat are at higher risk for certain cancers while other carnivores are not without a clear cause as to why. This prompted researchers to investigate the possible tumor-forming role of a sugar called Neu5Gc, which is naturally found in most mammals but not in humans.
The scientists found that feeding Neu5Gc to mice engineered to be deficient in the sugar (like humans) significantly promoted spontaneous cancers. The study did not involve exposure to carcinogens (which artificially induce cancers), further implicating Neu5Gc as a key link between red meat consumption and cancer.
“Until now, all of our evidence linking Neu5Gc to cancer was circumstantial or indirectly predicted from somewhat artificial experimental setups,” said principal investigator Ajit Varki, MD.
“This is the first time we have directly shown that mimicking the exact situation in humans—feeding non-human Neu5Gc and inducing anti-Neu5Gc antibodies—increases spontaneous cancers in mice.”
The team first conducted a systematic survey of common foods. They found that red meats (beef, pork and lamb) are rich in Neu5Gc, affirming that foods of mammalian origin such as these are the primary sources of Neu5Gc in the human diet. The molecule was found to be bio-available, too — which just means it can be distributed to tissues throughout the body via the bloodstream.
The researchers had previously discovered that animal Neu5Gc can be absorbed into human tissues. In this study, they hypothesized that eating red meat could lead to inflammation if the body’s immune system is constantly generating antibodies against consumed animal Neu5Gc, a foreign molecule. Chronic inflammation is known to promote tumor formation.
To test this hypothesis, the team engineered mice to mimic humans in that they lacked their own Neu5Gc and produced antibodies against it. When these mice were fed Neu5Gc, they developed systemic inflammation. Spontaneous tumor formation increased fivefold and Neu5Gc accumulated in the tumors.
“The final proof in humans will be much harder to come by,” Varki said. “But on a more general note, this work may also help explain potential connections of red meat consumption to other diseases exacerbated by chronic inflammation, such as atherosclerosis and type 2 diabetes.
“Of course, moderate amounts of red meat can be a source of good nutrition for young people. We hope that our work will eventually lead the way to practical solutions for this catch-22.”
Unfortunately, the study done in mice will probably be the somewhat final word on the matter and further research still needs to be done. However, it would be nice to at least understand why red meat consumption increases cancer risk and even find ways to prevent the problems that come from heavy consumption.
Samraj, A., Pearce, O., Läubli, H., Crittenden, A., Bergfeld, A., Banda, K., Gregg, C., Bingman, A., Secrest, P., Diaz, S., Varki, N., & Varki, A. (2014). A red meat-derived glycan promotes inflammation and cancer progression Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1417508112