Pancreatic cancer and lymphoma
Pancreatic cancer is the fourth most common cause of cancer death. Large geographical variation indicates diet and lifestyle as contributing to the risk of this disease.
Many studies show that meat increases the risk. The NIH-AARP Diet and Health Study found that men eating the most grilled and barbecued meat had a 50 per cent increased risk. Men and women consuming the most DiMeIQx had a 29 per cent increased risk. Another NIH-AARP study found links with fat, particularly from red meat and dairy foods but not from plant foods.
Studies from the US, Europe and Japan found that each daily 50g serving of processed meat increased the risk in men by 19 per cent. Men tend to eat more meat but it could be that haem iron was involved and women gained protection by losing iron through menstruation.
The EPIC-Oxford and the Oxford Vegetarian Study found that vegetarians and vegans were 50 per cent less likely to die from pancreatic cancer than meat-eaters. Another study of British vegetarians found the risk of pancreatic cancer was 27 per cent lower than in meat-eaters.
Another EPIC study found that for every 50g increase in poultry a day (three chicken nuggets or a third of a chicken breast) the risk of pancreatic cancer increased by 72 per cent. The same team found similar results for lymphomas and suggest drugs and antibiotics given to poultry to enhance growth and to treat disease may be involved.
These findings provide strong evidence that animal fat and meat play a role in the development of pancreatic cancer.
Pancreatic cancer is the fourth most common cause of cancer death worldwide with large geographical variation, which implies diet and lifestyle as contributors as risk factors for this disease (Rohrmann et al., 2013). Around 8,800 people are diagnosed with pancreatic cancer in the UK each year (NHS Choices, 2014c).
Meat intake has been positively associated with pancreatic cancer in many studies. The NIH-AARP Diet and Health Study cohort of 537,302 individuals, aged 50-71, investigated the association between meat, cooking methods, meat-mutagen intake and pancreatic cancer (Stolzenberg-Solomon et al., 2007). During five years of follow-up, 836 pancreatic cancer cases were recorded. Results showed that men consuming the most grilled and barbecued meat had a 50 per cent increased risk of pancreatic cancer. Men and women consuming the most DiMeIQx (an HCA found abundantly in well-cooked meat) had a 29 per cent increased risk. These findings indicate that meat, particularly meat cooked at high temperatures, plays a role in the development of pancreatic cancer.
A review of eleven studies, six from the US, four from Europe and one from Japan, found that each 50g per day (about one serving) of processed meat was associated with a 19 per cent increased risk of pancreatic cancer (Larsson and Wolk, 2012).
Few studies have examined associations between dietary fat and pancreatic cancer and their findings have been inconsistent. This may be due to the small number of patients diagnosed with pancreatic cancer and/or to the narrow range of fat intakes in these studies. The NIH-AARP study included a large number of people and wide range of fat intake from diverse food sources. This study observed significant links between pancreatic cancer and animal fat, particularly from red meat and dairy foods but did not observe any consistent association with fat from plant foods (Thiébaut et al., 2009). They concluded that animal fat is associated with an increased risk of pancreatic cancer.
How meat might cause pancreatic cancer
In the review of 11 studies from the US, Europe and Japan, the link between pancreatic cancer and red meat was only observed in men. The authors said that red meat consumption was on average higher in men than in women and suggested that if there is a threshold effect with an increased risk of pancreatic cancer only at high levels of red meat consumption, a positive association may be more likely to be detected in men. Another biologically plausible explanation for the observed differences between men and women is haem iron (abundant in red meat), which could enhance the growth of pancreatic cancer tumours (Stolzenberg-Solomon et al., 2007). Due to normal iron loss during menstruation, women do not accumulate such high iron stores as men. Higher levels of iron in the blood and higher percentage of iron saturation (iron to iron binding capacity) were associated with increased risk of subsequent pancreatic cancer in one prospective study (Friedman and van den Eeden, 1997).
Combined data from the EPIC-Oxford cohort and the Oxford Vegetarian Study (including 31,470 meat-eaters, 8,516 fish-eaters, 18,096 vegetarians and 2,228 vegans) found that, compared with meat-eaters, vegetarians and vegans had around 50 per cent lower mortality from pancreatic cancer (Appleby et al., 2016). When they excluded those who changed diet group during the study (possibly reflecting the onset of illness), compared with regular meat-eaters, vegetarians and vegans had around 50-60 per cent lower mortality. This reflects findings from another study of cancer in British vegetarians (Key et al., 2014). They found the risk of cancer is generally lower in vegetarians and vegans than meat-eaters, specifically 27 per cent lower for pancreatic cancer.
A link with poultry was found in the huge EPIC study looking at the links between meat and fish with pancreatic cancer (Rohrmann et al., 2013a). During the study, 865 pancreatic cancer cases were recorded among 477,202 participants from 10 European countries. The consumption of red and processed meat was not associated with pancreatic cancer in this study. However, for every 50g of poultry per day (that’s just three chicken nuggets or a third of a chicken breast) the risk of pancreatic cancer increased by 72 per cent.
When the same EPIC team found a similar result for lymphomas and poultry they suggested antibiotics and/or coccidiostats (drugs given to poultry or cattle to prevent the growth and reproduction of certain parasites) may be involved (Rohrmann et al., 2011). Chicken and turkeys are often treated with coccidiostats and antibiotics to enhance their growth and to treat and prevent disease. The frequency of antibiotic use has been associated with the risk of non-Hodkin lymphoma in some studies (Chang et al., 2005; Kato et al., 2003).
The EPIC team also suggest another possibility, oncogenic animal viruses. Poultry may contain viruses that cause the development of tumours, especially if the meat is not cooked properly. Oncogenic animal viruses have been suspected as a cause of non-Hodgkin lymphoma among people working with animals or in meat-processing for some time but meat consumption has not been connected with transmission of oncogenic viruses yet. However, studies have found a lower risk of non-Hodgkin lymphoma in women consuming well-done meats instead of rare or rare-medium meats (Chiu et al., 1996; Zhang et al., 1999). So you are damned if you cook it, and damned if you don’t!