Scientists have long known that consumption of red meat is linked to the development of certain types of cancers in humans. A team of researchers now believes this is because the body sees red meat as a foreign invader, which triggers an immune response involving antibodies that cause inflammation, and eventually cancer.
The researchers, based at the University of California, San Diego School of Medicine, reported their findings in the Proceedings of the National Academy of Sciences.
Specifically, the researchers believe a sugar that naturally occurs in animals but not humans, acid N-glycolylneuraminic acid (Neu5Gc), is the culprit. Pork, beef and lamb all contain high concentrations of Neu5Gc. The researchers believe that, because other mammals’ bodies naturally produce Neu5Gc, they can eat the sugar without adverse health effects. However, because humans do not naturally produce the sugar, when it enters the human body it triggers an immune response, which can be destructive over time.
The researchers studied this by feeding Neu5Gc to mice engineered to be deficient in the sugar, like humans. They found that, when fed Neu5Gc, the mice developed evidence of systemic inflammation. Over the long term, they had a five-fold increase in the development of carcinomas. The researchers also believe that similar mechanisms may contribute to the association between red meat consumption and the development of atherosclerosis and type 2 diabetes.
“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 in a press release.
“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,” he continued, while noting that this will be significantly harder to prove in humans.
Varki said, however, that this does not necessarily mean that everyone should give up red meat.
“Of course, moderate amounts of red meat can be a source of good nutrition for young people,” he said. “We hope that our work will eventually lead the way to practical solutions for this catch-22.”