As The Telegraph reports, scientists from the University of California in San Diego believe it mainly has to do with sugar.
While humans, as omnivores, can tolerate eating meat (and have been doing so for many years, but not in the quantity witnessed today) there is unique sugar named Neu5Gc, found in most mammals but not in humans, that triggers an immune responsewhich causes inflammation.
Mice were used for the study which found that all the evidence linking Neu5Gc to cancer was circumstantial or indirectly predicted from experimental setups. According to the scientists, this is the first time they mimicked the exact situation in humans through feeding non-human Neu5Gc and inducing anti-Neu5Gc antibodies. This increased spontaneous cancer in mice.
This sugar can be found in red meats (pork, beef, and other livestock), cow’s milk and certain cheeses. Because the human body is not capable of producing this sugar naturally when the sugar is absorbed into the tissues, it is perceived as a foreign invader and activates the immune system. It is suspected that over time, the chronic inflammation caused by the immune system response plays a role in the development of cancer.
Thus, those who consume red meat on a regular basis are likely to suffer a stronger reaction than those who ingest red meat occasionally.