31 Dec Study Links Red Meat To Inflammation and Tumor Formation
Ajit Varki MD
Distinguished Professor of Medicine and Cellular & Molecular Medicine , Co-Director, Center for Academic Research and Training in Anthropogeny, Co-Director, Glycobiology Research and Training Center
University of California, San Diego, La Jolla, CA
Medical Research: What is the background for this study? What are the main findings?
Dr. Varki: For the past decade, there has been increasing evidence that people who consume red meat (beef, pork, lamb) are at a higher risk for certain kinds of cancers. Although red meat is a high quality source of protein, iron and vitamins, too much consumption may be harmful to humans. While there are other hypotheses under consideration, we focused on a non-human sugar molecule called Neu5Gc in red meat that could explain the link to cancer risk.
We extensively studied various foods and concluded that red meat (particularly beef) is rich in Neu5Gc. In contrast poultry, fish steaks and hen eggs have little or no Neu5Gc. From previous studies, we knew that animal-derived Neu5Gc could be incorporated into human tissues. In this study, we hypothesized that eating red meat could lead to inflammation if the body’s immune system targets the foreign Neu5Gc. Chronic inflammation is also known to instigate or promote tumor progression.
To test this hypothesis, we used mice engineered to be similar to humans in that they lacked Neu5Gc, and also produced antibodies against it. When these mice were fed Neu5Gc, they developed systemic inflammation. Tumor formation increased fivefold and Neu5Gc accumulated in the tumors, proving the hypothesis. None of the various control groups of mice showed this effect.
Medical Research: What should clinicians and patients take away from your report?
Dr. Varki: While this mouse model shows that Neu5Gc in red meat is likely detrimental to humans, it is important to remember that red meat is nutritious and further research is necessary to define safe limits of consumption. Those who eat red meat are in a Catch-22 situation! On the other hand, modern fortified diets make red meat an optional component. This work may also explain potential connections of red meat consumption to other diseases exacerbated by chronic inflammation, such as cardiovascular diseases (heart attacks, strokes, and Type 2 diabetes).
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Varki: The next step, of course, is to investigate the role of Neu5Gc in humans, and specific diseases such as colorectal cancer. We are also researching practical ways to rid the body of Neu5Gc and possibly reduce the cancer risk.
Annie N. Samraj, Oliver M. T. Pearce, Heinz Läubli, Alyssa N. Crittenden, Anne K. Bergfeld, Kalyan Banda, Christopher J. Gregg, Andrea E. Bingman, Patrick Secrest, Sandra L. Diaz, Nissi M. Varki, and Ajit Varki
PNAS 2014 ; published ahead of print December 29, 2014, doi:10.1073/pnas.1417508112