Previous studies have specified that consuming red meat increases the risk of cancer. A new study has examined the eat metabolic pathway involved which involves the possible tumor-forming role of a sugar called Neu5Gc, which is naturally found in most mammals but not in humans. It was determined that red meats (beef, pork and lamb) are rich in Neu5Gc, confirming that foods of mammalian origin such as these are the primary sources of Neu5Gc in the human diet.
Feeding Neu5Gc to mice engineered to be deficient in the sugar (like humans) significantly promoted spontaneous cancers. The study did not investigate other exposure to carcinogens or artificially inducing cancers, further implicating Neu5Gc as a key link between red meat consumption and cancer.
A mouse model was engineered to mimic the human anatomy as 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.
“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, Distinguished Professor of Medicine and Cellular and Molecular Medicine and member of the UC San Diego Moores Cancer Center. “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.”
Eating red meat leads to chronic inflammation in the body as the body’s immune system is constantly generating antibodies against the Neu5Gc sugar, a foreign molecule.
“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.”
Annie N. Samraj, Oliver M. T. Pearce, Heinz Läubli, Alyssa N. Crittenden, Anne K. Bergfeld, Kalyan Banda, Christopher J. Gregg, Andrea E. Bingman, Patrick Secrest, Sandra L. Diaz, Nissi M. Varki, and Ajit Varki. A red meat-derived glycan promotes inflammation and cancer progression. PNAS, December 2014 DOI: 10.1073/pnas.1417508112