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THE epidemiological study that came out two years ago and declared that there was "convincing" evidence to link consuming red meat with cancer -- specifically colorectal cancer -- was flawed, and now, the author of the report has admitted it and has promised to write a letter to the U.S. Department of Agriculture saying so.
The study, an intense literature review of previous studies -- a study of studies -- was conducted by the World Cancer Research Fund (WCRF) and American Institute of Cancer Research (AICR) and recommended that the consumption of red meat (beef, pork, lamb) and processed meats should be limited to 18 oz. per week due to the cancer link (Feedstuffs, Nov. 5, 2007).
In response, the National Cattlemen's Beef Assn. (NCBA), through beef checkoff funds, commissioned Exponent Health Sciences to conduct its own review, which found "no conclusive evidence" of such a link (Feedstuffs, Feb. 25, 2008).
However, USDA's Center of Nutritional Policy & Promotion, which houses the advisory committee that will write USDA's 2010 Dietary Guidelines, indicated in April that it would defer to the WCRF/AICR work on a number of diet and cancer questions, NCBA executive director for human nutrition research Shalene McNeill told Feedstuffs.
Accordingly, NCBA commissioned Exponent to conduct a review of the WCRF/AICR study, specifically as it pertained to colorectal cancer, she said.
The review was led by Exponent senior managing scientist Dr. Dominik D. Alexander. Exponent is a scientific practice that performs risk assessments across several environmental and public health issues.
Missed by seven
Alexander, in a letter to the co-executive secretary of USDA's advisory committee, noted that the "totality" of available epidemiological evidence does not support "a causal association" between consumption of red meat and cancer, including colorectal cancer.
He said findings from cohort studies, i.e., other studies like WCRF/AICR's, have shown "weak" associations that are not statistically significant, that vary by anatomic sites within the colorectum and by gender and that are subject to diverse definitions of categories of meat and measures of intake.
Specifically, Alexander made the following key points:
* WCRF and AICR omitted several important studies on colorectal cancer in their report;
* A number of "analytical inconsistencies" and "data extraction errors" were identified in the WCRF/AICR report -- indeed, he said WCRF/AICR overestimated the risk between eating red meat and cancer "by a factor of seven," and
* A number of the criteria employed by WCRF and AICR in making the causal association conclusion were inconsistent with "established scientific guidelines."
Accordingly, Alexander said the WCRF/AICR study "should not be viewed as an accurate or complete summary" of the epidemiological literature on the issue and cautioned against deferring to it in developing dietary guidelines.
He pointed out that the Exponent review of the WCRF/AICR study has been published in and is under review by several scientific journals.
Alexander's full report to USDA is posted at USDA's Dietary Guidelines web site at http://usda-cnpp.entellitrak.com by clicking on "here" and going to page 9 to his submission on 6/30/09.
Effective dialogue
McNeill noted that, unbeknownst to NCBA, a number of other researchers late last year and earlier this year came out with independent reports making many of the same points.
In particular, Dr. Stewart Truswell, emeritus professor in human nutrition at the University of Sydney in Australia, in an editorial in the April issue of the American Journal of Clinical Nutrition, said:
* The WCRF/AICR report omitted 13 cohort studies involving 1.6 million people -- including a large study conducted by the American Cancer Society -- in which 11 of the studies found no significant association between eating red meat and cancer;
* The report omitted a comparison of several groups of socially matched meat-eating consumers and vegetarians in which there was no difference in mortality from colorectal cancer between the two groups;
* The report did not refer to follow-up work by certain of its research sources that drew different conclusions, and
* The report did not refer to recent work by researchers that involved more subjects and reached different conclusions.
McNeill said Alexander and NCBA took the Exponent and other studies to WCRF and AICR not in a confrontational way but to determine if they would acknowledge their report's errors, and they: (1) did so, (2) said they would address the errors in continuous updates and (3) said they would write to the USDA advisory committee to inform it of the errors and omissions.
She emphasized that WCRF and AICR have been "extremely responsive," even to the extent of asking Alexander to serve on the WCRF/AICR review board.
"This has not been a public spat but an effective engagement in dialogue," McNeill said. | 
