New research suggests that a sugar molecule in red meat promotes inflammation and cancer progression.

Researchers from the University of California -San Diego 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 or artificially inducing 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," Ajit Varki, principal investigator of the study, said in a statement. "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."

For the study, researchers 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, meaning it can be distributed to tissues throughout the body via the bloodstream.

They had previously discovered that animal Neu5Gc can be absorbed into human tissues.

They then 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.

However, he noted that 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," he said.

The findings are detailed in the Proceedings of the National Academy of Sciences.