Researchers in Sweden who analyzed several prospective studies found an increased risk of pancreatic cancer associated with processed meat consumption. They also found that eating red meat is linked to pancreatic cancer among men.
As more people are becoming aware that their lifestyle choices, including dietary habits, can have profound effects on health outcomes, studies such as this one can affect whether an individual chooses to eliminate or add a particular food to his or her diet. They can also add to the public dietary recommendations such as those published by the American Cancer Society.
The meta-analysis study, published in the British Journal of Cancer shows increasing red meat consumption by 120 grams a day increases the relative risk of pancreatic cancer. That’s an extra quarter-pound burger (whether adding processed cheese on top increases the risk is not known) or 4 pieces of bacon. However, the increase in risk is only 13%, which is not statistically significant.
When the effects on men and women were analyzed separately, there was a statistically significant effect on pancreatic risk among men who consume red meat. The increased risk of pancreatic cancer was almost 30%. The same comparison among women did not show an increased risk of the cancer. Because men had greater red meat consumption overall, the authors reason that there may be a threshold effect of pancreatic cancer risk detected only among men. The finding may also have occurred by chance.
Dr. Susanna Larsson, lead author of the study stated that the difference between the effects of red meat among men and women was unexpected. She added that she does not believe that this meta-analysis is enough to change people's dietary habits and that more follow-up studies are needed.
No sex differences were found for processed meat consumption and risk of pancreatic cancer. However, for every extra 50 grams of processed meat consumed per day, the relative risk increases by 19% for both sexes.
Speaking with CancerNetwork, John Milner, PhD, head of the Nutritional Science Research Group at the National Cancer Institute (NCI) said that he was not terribly surprised by the by the findings and pointed out that these results are consistent with a 20% increased risk of colorectal cancer and red meat consumption.
Dr. Larsson and colleague at the Division of Nutritional Epidemiology at the Karolinska Institute in Sweden used 11 prospective studies with over 6,000 pancreatic cancer patients to analyze the effect of processed and red meat consumption on cancer development. All studies were conducted between 1966 and November of 2011 and had pancreatic cancer incidence or mortality as their outcomes. Of those studies, 6 were conducted in the United States, 4 in Europe, and 1 in Japan.
The roles that environmental factors play in cancer development are difficult but important to identify. It is known that stomach and gastroinstestinal cancers are linked to higher red and processed meat consumption but whether dietary factors affect the development of pancreatic cancer are still not completely clear.
Is this study enough to convert red-meat eaters to vegetarians or at least to pescetarians? Probably not since the actual pancreatic cancer risk from having the occasional steak or burger is still quite low. The current lifetime risk of developing pancreatic cancer is about 1.4%. According to this study, that risk goes up to 1.7% with a daily burger or breakfast sausage. But, a relatively high red-meat diet also effects cardiovascular health. Smoking may additionally affect pancreatic cancer. Based on current evidence, not eating red meat daily may be good in the long run for your pancreas, and your entire body.
The importance of the study is the awareness that the pancreas is exposed to the nitrates and N-nitroso compounds found in red and processes meats through the bloodstream and that these compounds are carcinogenic. Animal models have been used to show that N-nitroso compounds can induce pancreatic cancer, according to the study authors.
Dr. Milner of the NCI also pointed out that the study did not do a good job of outlining confounding factors that may have had importance influence on the outcomes. People that eat a significant amount of red meat tend to eat fewer fruits and vegetables. Whether it is the compounds in red and processed meat or a lack of fresh fruit and vegetables is not clear from the study published by Larsson and colleagues.
Further prospective studies looking at a single environmental factor and subsequent multifactorial studies will shed further light on the role of diet to pancreatic cancer development. The challenge will be to control for other confounding factors such as genetic predisposition, weight, comorbidities, and exercise.
"Diet is incredibly important in determining one's cancer risk and the behavior of tumors. People don't respond to food the same, which has to do with our genetic makeup," Milner said.
Highlighting this point, Milner believes that there is likely a subgroup effect that is diluted by general population studies, citing a 13% overall risk that is likely higher in particular individuals. Certain individuals may have differences in gene expression that are more susceptible to the harmful effects from exposure to the compounds that result from meat digestion. The relative risk for these individuals may be higher than for the general population.
Teasing out potential environmental causes and the individuals that are most affected by them may help to prevent new cases of pancreatic cancer. Pancreatic cancer is one of the fastest developing types of tumors with a 5-year survival of only 5.5% according to the Surveillance, Epidemiology, and End Results (SEER) cancer statistics from the NCI. Whether red and processed meat consumption is a true, independent risk factor for pancreatic cancer is still an open question.