‘Weak’ evidence for red meat link with cancer, scientists claim

12-Mar-2014 - Last updated on 12-Mar-2014 at 10:54 GMT

Studies linking red meat with colorectal cancer have led to dietary advice to cut meat intakes – but there are still scientific uncertainties in the evidence, according to a review published in Meat Science.

The paper is authored by 23 scientists who met in November at a Norwegian conference on the health effects of red meat. Among other issues, they challenge the validity of studies that centre on feeding lab animals large quantities of red or processed meat, without adding any dietary components known to keep the gut healthy, like fibre, vegetables, or calcium-rich foods. These studies therefore create dietary conditions unlike human diets.

In humans, the paper’s authors claim that studies comparing colorectal cancer (CRC) rates in vegetarians and meat eaters are inconsistent.

“One study found a lower incidence of CRC for vegetarians, another found no difference between meat eaters and vegetarians, and yet another detected a lower incidence in the meat eaters,” they wrote. “Hence, the relationship seems to be complex and not only depend on the meat intake but also on the total composition of the diet.”

Cause-and-effect relationship?

“Associations may also depend on genetic or environmental backgrounds: The Sami people of Northern Europe, who are reindeer-herders and have high levels of red meat intake, have lower levels of colon cancer than reference populations from the same regions, yet an opposite effect was found for Alaska Natives.

“…Observational studies of this topic cannot fully correct for all confounding factors and are unlikely to establish a cause-and-effect relationship between meat consumption and CRC by themselves.”

The researchers also point out that our diets tend to be complex, with components eaten with red or processed meat helping to mitigate CRC risk – or generally unbalanced diets worsening risk.

Ways to tackle risk

They also suggest strategies to reduce risk of colorectal cancer from meat consumption, including modifying meat composition through feed or breeding, changing processing methods, and improving meals and diets in general.

“This may not just reduce risk of CRC but may also be beneficial for reduction of obesity and cardiovascular diseases. In order to achieve this, researchers need to collaborate with the meat industry and public health authorities,” they wrote.

Studies linking red and processed meat with cancer have led the UK government, the Nordic Nutrition Recommendations and French dietary guidelines to recommend limiting consumption – to less than 70 g per day in the UK, for example, and less than 500 g of cooked red meat or processed meat in Norway. FAOSTAT data suggest that UK consumption of pork, poultry, lamb and beef is about 240 g per person per day, about 275 g in Spain, and about 140 g in Norway.

This latest paper comes on the heels of a study that found a four-fold increase in cancer death risk among middle-aged people with the highest intakes of animal protein – although it also found that high animal protein intakes had a protective effect among older consumers.

Source: Meat Science

http://dx.doi.org/10.1016/j.meatsci.2014.02.011

“The role of red and processed meat in colorectal cancer development: A review, based on findings from a workshop”

Authors: Marije Oostindjer, , Jan Alexander, Gro Vang Amdam, Grethe Andersend, Nathan S. Bryan, Duan Chen, Denis E. Corpet, Stefaan De Smet , Lars Ove Dragsted, Anna Haug, Anders H. Karlsson, Gijs Kleter, Theo M. de Kok, Bård Kulseng, Andrew L. Milkowski, Roy J. Martin, Anne-Maria Pajari, Jan Erik Paulsen, Jana Pickova, Knut Rudi, Marianne Sødring, Douglas L. Weed, Bjørg Egelandsdal