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Concurrent Session: Evaluating the Relationship of meat & cancer

Saturday, May 7, 2016
10:45am - 12:00pm

Suzor-Coté/Delfosse

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Chair: Dr. Vera Mazurak

The potential relationship between red meat consumption and cancer risk continues to be a controversial topic debated in the scientific community. Given that cancer is a topic of public health interest this session will provide important context and balanced perspectives on the role of red meat in the development of cancer. It is an opportunity to examine if the totality of the evidence on red meat and cancer is adequate to support conclusions by the International Agency for Research on Cancer.


Is the totality of evidence on red meat and cancer adequate for valid conclusions?
David M. Klurfeld, Ph.D

While certainty in public health decisions is not essential, standards of evidence should be met. These include data on human dietary exposure and risk of disease, animal studies, and validated mechanistic studies. The recent decision by the WHO’s International Agency for Research on Cancer was driven primarily by observational epidemiology of colon cancer with support from inconclusive potential mechanisms. Animal data were not sufficient to reach any conclusion. Observational studies of weak associations should be viewed skeptically particularly in dietary surveys that include substantial confounding and bias. The IARC working group concluded that bias or confounding were unlikely in processed meat studies but existed in red meat studies. However, the same methods were used for both food products and many studies reported on both types of meat, verifying similar confounders and bias. In addition, most cohort studies used only a single baseline questionnaire with follow-up that ranged to decades, assuming intake did not change. An additional weakness is the inability of such questionnaires to accurately estimate protein or energy intake.  Most importantly, the working group ignored two large trials of low fat diets that reduced red and processed meat but found no reduced risk of colon cancer or polyps. Considerable uncertainty remains about the relationship of any dietary factor with cancer.


The Epidemiology of Red and Processed Meat Consumption and Colorectal Cancer
Dominik D. Alexander, PhD, MSPH

The potential role that red meat or processed meat intake plays on cancer risk has been widely debated in scientific communities. To update the state-of-the-science on this complex topic area, we conducted a systematic quantitative assessment of the epidemiologic literature. Data from 27 independent prospective cohort studies were meta-analyzed using random-effects models, and sources of potential heterogeneity were examined through subgroup and sensitivity analyses. A comprehensive examination of potential dose-response trends was performed as well. Based on our series of meta-analyses, we observed a weakly elevated summary relative risk for all studies of red meat; however, statistically significant heterogeneity was present. Sources of variation included the type of meat analyzed, gender, adjustment for confounding factors, and study country. No clear patterns of dose-response were apparent and most individual studies did not observe statistically significant findings. Associations for processed meat and colorectal cancer are slightly stronger in magnitude and consistency than for fresh red meat. In conclusion, the currently available epidemiologic data are not sufficient to support an independent relationship between red meat and processed meat consumption and colorectal cancer.

Joint Session Sponsored by:


Chair:


Speakers:

Dr. David M. Klurfeld

National Program Leader for Human Nutrition, Agricultural Research Service, U.S. Department of Agriculture


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