November 14, 2008
Red Meat Molecule Boosts Human Cancer Risk?

Why do people who eat a lot of meat and milk products get cancer more often? A glycan (a type of polysaccharide) molecule present in red meat and milk products might elicit an immune response that stimulates tumor growth.

Researchers at the University of California, San Diego School of Medicine, led by Ajit Varki, M.D., have shown a new mechanism for how human consumption of red meat and milk products could contribute to the increased risk of cancerous tumors. Their findings, which suggest that inflammation resulting from a molecule introduced through consumption of these foods could promote tumor growth, are published online this week in advance of print publication in the Proceedings of the National Academy of Sciences (PNAS).

Varki, UC San Diego School of Medicine distinguished professor of medicine and cellular and molecular medicine, and co-director of the UCSD Glycobiology Research and Training Center, and colleagues studied a non-human cellular molecule called N-glycolylneuraminic acid (Neu5Gc). Neu5Gc is a type of glycan, or sugar molecule, that humans don't naturally produce, but that can be incorporated into human tissues as a result of eating red meat. The body then develops anti-Neu5Gc antibodies an immune response that could potentially lead to chronic inflammation, as first suggested in a 2003 PNAS paper by Varki.

In mice the combination of the Neu5Gc glycan and immune antibodies against Neu5Gc caused tumors to grow quicker. Drugs that reduce inflammation might cut cancer risk by suppressing an immune response to Neu5Gc.

Using specially bred mouse models that lacked the Neu5Gc molecule mimicking humans before the molecule is absorbed into the body through ingesting red meat the researchers induced tumors containing Neu5Gc, and then administered anti-Neu5Gc antibodies to half of the mice. In mice that were given antibodies inflammation was induced, and the tumors grew faster. In the control mice that were not treated with antibodies, the tumors were less aggressive

Others have previously shown that humans who take non-steroidal anti-inflammatory drugs (commonly known as NSAIDs) have a reduced risk of cancer. Therefore, the mice with cancerous tumors facilitated by anti-Neu5Gc antibodies were treated with an NSAID. In these animals, the anti-inflammatory treatment blocked the effect of the Neu5Gc antibodies and the tumors were reduced in size.

"Taken together, our data indicate that chronic inflammation results from interaction of Neu5Gc accumulated in our bodies from eating red meat with the antibodies that circulate as an immune response to this non-human molecule and this may contribute to cancer risk," said Varki.

This result is important because it suggests you probably can't neutralize all the cancer risk associated with greater meat and milk consumption. As long as you are eating sources of Neu5Gc you are boosting your risk of cancer.

Though not all studies find a strong link between cancer and red meat consumption. Another recent study found that the risk small intestine cancer seemed to be boosted by saturated fat consumption and not by red meat. Of course a lot of red meat is high in saturated fat. This result holds out the hope that lean red meat might not boost your cancer risk.

Cross and other researchers from the National Cancer Institute used food frequency questionnaires to track food intake in a half million men and women enrolled in the NIH -AARP Diet and Health study over an eight-year period. Through state cancer registries and national death indexes researchers noted the development of 60 adenocarcinomas and 80 carcinoid tumors of the small intestine.

While findings showed no clear connection between red and processed meat and these tumors, they suggested a noticeably elevated risk for carcinoid tumors in the small intestine in association with saturated fat intake.

If you eat more fruits and vegetables they will displace less healthy foods from your diet. Add omega 3 fatty acids since they probably counteract the harmful effects of too much omega 6 fats from red meat and dairy.

Share |      Randall Parker, 2008 November 14 12:50 AM  Aging Diet Cancer Studies

BBM said at November 14, 2008 10:00 AM:

Seems like you could breed animals or engineer them to lack that polysaccharide rather easily.

Unless it plays some crucial role in the organism, of course.

In said at November 14, 2008 10:33 AM:

Grassfed red meat has a superior fatty-acid profile (more omega 3's) than grain fed factory farmed animals.

Why not push for more natural, organic animal husbandry practices for better health?

Tom Bri said at November 15, 2008 2:49 PM:

So, studies show little or no increased risk of cancer with meat consumption. But we should avoid meat anyway, because other studies show that meat should raise cancer risk, even though it doesn't. OK.

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