Researchers show why red meat is linked to cancer
Recent advice from the World Cancer Research Fund cautioned against eating more than 500g of red meat (beef, lamb or pork) per week. It also advised restricting consumption of processed meats, such as bacon, ham and salami, to as little as possible.
“Convincing evidence” that these types of meat increase the risk of bowel and other cancers means people should seriously think about cutting down, it said.
Several studies have linked red-meat consumption to various types of cancer, particularly colorectal, prostate, breast, ovarian and lung cancers.
Now, further evidence comes with a recent study conducted at the University of California San Diego, which points to Neu5GC, a sugar molecule found in beef, pork and lamb.
While Neu5GC is found naturally in most mammals, it is not found in humans, causing the body to perceive it as a foreign substance and the immune system to attack it. In turn, this causes inflammation in the body, which is known to promote the formation of tumours over time.
The scientists cautioned that the same process could occur when people consume fish eggs, whole milk, and certain cheeses, all of which contain Neu5GC.
Chicken and fish, on the other hand, contain little or no Neu5GC.
Lead researcher Dr Ajit Varki, said the Neu5GC phenomenon is unprecedented.
“In this case, the foreign sugar is like a Trojan Horse. It becomes part of your own cells,” he said.
“This is the first example we know of something that’s foreign, gets totally incorporated into you despite the fact that your immune system recognises it.”
Dr Varki went on to explain that Neu5Gc plays the role of “gasoline on the fire,” boosting the cancer risk, while apparently not being the ultimate cause of the disease.
In the study, which was published online in the Proceedings of the National Academy of Sciences, Dr Varki and his colleagues fed Neu5GC to two groups of mice.
One group naturally had Neu5GC, while the other was genetically engineered to mimic human biology by no longer having the molecule.
The genetically engineered mice had a cancer rate that was more than five times that of the others.
“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,” Dr Varki said.
He nevertheless cautioned that the final proof in humans “will be much harder to come by.”
On a more general note, he indicated that the 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.
He nevertheless does not advise eliminating red meat from the diet, noting 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 added.