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Annals of Oncology Editorial Challenges World Cancer Research Fund Conclusions

Monday, October 13, 2008

(American Meat Institute)

An editorial by leading cancer researchers in the October 2008 Annals of Oncology challenged the 2007 World Cancer Research Fund (WCRF) report conclusions and argued that media information generated by the group should have been more cautious and less definitive.  The editorial was written by scientists with the International Agency for Research on Cancer in France.

Headlines on stories about the 2007 WCRF report, triggered largely by press releases issued by the group and its U.S. affiliate, the American Institute for Cancer Research, warned that red meat should be limited to 18 oz of meat per week and that there was no safe level of processed meat consumption.  The editorial chastised WCRF for its focus on individual foods as opposed to dietary patterns and for its failure to highlight the huge increase in cancer risk posed by tobacco use.

According to the piece, the media coverage generated by WCRF’s ten key recommendations to reduce cancer risk compounded the problem.  All recommendations focused on diet and weight control and omitted any mention of the risk posed by tobacco exposure, leading the public to believe that nutrition and weight played the more significant role in cancer prevention, something not supported by the literature. The authors also expressed concern that WCRF’s 'best advice' for cancer prevention failed to mention the importance of a variety of established cancer risk factors including sun behavior, occupational exposures, chronic infections and use of exogenous hormones.

They echoed concerns expressed by many experts – and by AMI itself – that the public is at risk of a terminal case of what some have called nutrition whiplash.  “The public are frequently receiving confused and confusing messages: so too are the media. The scientific community has a collective responsibility to transmit clear messages to the general community and not those which favour their position or findings,” they said.  “In view of the fragile grounds on which the conclusions of WCRF report on diet and cancer are based on, the information to the media should have been more cautious,” noting that their press releases “left a clear indication that cancer prevention depends on stopping eating bacon and avoiding drinking sodas.”

The authors expressed concern about a focus on specific foods as opposed to food patterns.   “The substantial review of the evidence in the WCRF report demonstrates that there is no discernible association between many forms of cancer and specific dietary practices. There are still some very interesting hypotheses to pursue, such as the value of an approach on the basis of the food patterns (e.g. the Mediterranean diet score [20]) rather than individual foods and nutrients, but the cupboard is remarkably bare.”

The 2007 WCRF report was a follow-up to a 1997 report, the first one ever done by WCRF.  In the earlier report, the power of fruits and vegetables to prevent cancer was deemed to be convincing, yet in the more recent edition, WCRF was less enthusiastic about their value and rated their protective effect as “probable.” “This major change in classification of one of the few agents classified by WCRF in the category of strongest evidence in 1997 [the protective effect of fruits and vegetables] casts doubt on the rationale to classify 'convincing' to the evidence linking high meat intake to colorectal cancer in the current report. This also raises questions about the evaluation process and about the robustness of the classification system,” the authors wrote.

AMI has raised significant concerns about the report’s credibility.  A critical issue, in AMI’s view, is the fact that the 2,300-page systematic literature review that should be the basis for WCRF’s conclusions said there was no plausible biological mechanism for a link between red meat and colon cancer, while the report concluded there was “convincing evidence of a link.”

 

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