How Strong are Links between Meat and Cancer?

A new study published in the British Journal of Cancer and produced by researchers at the Karolinska Institutet in Stockholm has concluded that there is an enhanced risk of pancreatic cancer by eating processed meats.
calendar icon 17 January 2012
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The study is the latest is a series of research reports that has links the consumption of processed meats and red meat with various cancers.

In November last year a research team, led by John Witte of University of California, San Francisco linked increase consumption of ground red meat and processed meats to prostate cancer.

The researchers also said they found that the correlation was primarily driven by red meat that was grilled or barbecued, especially when well done.

And in the UK last year, a report from the Scientific Advisory Committee on Nutrition (SACN), which reviewed evidence on the links between red and processed meat and bowel cancer, concluded that red and processed meat probably increases the risk of bowel cancer and people who eat around 90g or more should consider cutting down to reduce their risk.

With a succession of such reports being published, it is a wonder that red meat and processed meat products are not sold with a health warning as seen on the side of cigarette packets.

Against the battery of reports that have been appearing, the red meat industry has not been the speediest to put up its counter claims.

However, the American Meat Institute has poured cold water on the claims from the World Cancer Research Fund over the connections between red and processed meats and cancer.

The AMI said earlier this year that the renewed claims should be met with scepticism as they are not supported by the full evidence and they conflict with the US Dietary Guidelines, which say that red and processed meat can be a healthy part of balanced diet.

The AMI also said that the WCRF's original 2007 report was based upon very weak findings and many contradictions, and was questioned by many groups, including the International Agency for Research on Cancer.

Other studies have also found holes in the WCRF's report. An editorial in the Annals of Oncology said: "The substantial review of evidence in the WCRF report demonstrates that there is no discernible association between many forms of cancer and specific dietary practices."

Another study by Dr Stewart Truswell, of the University of Sydney, and Dr Dominik Alexander, of Exponent, whose review was published in the American Journal of Clinical Nutrition, highlighted a number of errors and omissions in the WCRF review of red and processed meat and colorectal cancer. These included analytical inconsistencies and data extraction errors in the evidence presented which could have contributed to an overestimate of the association between eating red meat and the risk of CRC.

The conclusion of Dr Alexander's review was that "there is no conclusive evidence of causal relationship" between eating meat and colorectal cancer.

Even the latest report from the Karolinska Institutet has clauses within it that also cast doubt on its own conclusions.

The report says: "Our study has some limitations. First, as a meta-analysis of observational studies, we cannot rule out that individual studies may have failed to control for potential confounders, which may introduce bias in an unpredictable direction. All studies controlled for age and smoking, but only a few studies adjusted for other potential confounders such as body mass index and history of diabetes.

"Another limitation is that our findings were likely to be affected by imprecise measurement of red and processed meat consumption and potential confounders."

The research looked at 13 studies into red and processed meat consumption and cancer. Having discarded two of the studies conducted a meta-analysis of the remaining 11 studies, of which seven provided data for the consumption of processed meats.

"When results from all studies were combined, an increase of 50 g per day of processed meat consumption was associated with a statistically significant 19 per cent increased risk of pancreatic cancer," the study said.

It added: "The positive association between processed meat consumption and pancreatic cancer risk was attenuated and not statistically significant in a sensitivity analysis excluding one of the studies (No¨thlings et al, 2005).

"There was no overall association between red meat consumption and risk of pancreatic cancer. However, red meat consumption was statistically significantly positively associated with pancreatic cancer risk in men. Red meat consumption was on average higher in men than in women.

"If there is a threshold effect with an increased risk of pancreatic cancer only at very high levels of red meat consumption, a positive association may be more likely to be detected in men. The observed positive association in men may also be a chance finding."

Despite the potential limitations in findings, the Swedish study concludes that there is a "statistically significant positive association between processed meat consumption and risk of pancreatic cancer. Red meat consumption was not associated with risk of pancreatic cancer overall, but was positively associated with risk in men".

Further Reading

- You can view the full report from the Karolinska Institutet by clicking here.

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