CORRESPONDENCE

Re: Meat, Fish, and Colorectal Cancer Risk: The European Prospective Investigation into Cancer and Nutrition

Ulrike Gonder, Nicolai Worm

Correspondence to: Ulrike Gonder, DIPL OEC TROPH, Taunusblick 21, D-65510 Huenstetten, Germany or Nicolai Worm, Maxhoehe 40, D-82335 Berg, Germany (e-mail: nicolai.worm{at}t-online.de).

We read with interest the article by Norat et al. (1) about meat, fish, and colorectal cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort, which found no statistically significant association between the intake of red meat and colorectal cancer. Only when red and processed meats were combined was the observed positive association statistically significant. We would like to ask why the authors did not mention in their abstract the fact that red meat alone does not statistically significantly increase the relative risk and why they did not adjust their data for vegetable intake. Because vegetables and fruit are a good source of fiber and folate and reduce the energy density of a meal, all of which could diminish colorectal cancer risk, they are an important confounding factor. The cross-classification of red and processed meat intake with fiber intake clearly showed no increase in cancer risk if both intakes were in the highest category. The same was true for high fish intake. Many people enjoy eating red meat, fish, and poultry but do not eat processed meat.

Although the authors choose their wording very carefully, stating only that they found a "positive association," the media took the results of this study as a proof for a causal relationship between red meat consumption and colorectal cancer. We want to point out that such an association is far from proven, as none of the prospective European studies published to date found a statistically significant association (25). The authors state that they could not explain the association, and there is no known mechanism. One possible explanation could be the higher content of heme iron, but in the same issue of the Journal, Chan et al. (6) published data indicating that dietary iron was not associated with colorectal adenoma in women. In addition, it was recently shown that chlorophyll from green vegetables prevents the cytotoxic and hyperproliferative effects of heme in a rat model (7).

The EPIC study offers an important opportunity to learn more about diet and cancer. Its results, however, should be communicated in a very clear way because otherwise it would only increase the already existing confusion among consumers and health care providers. Because lean (red) meat is an important contributor to mineral, vitamin, and protein nutrition and many people like to eat meat, we feel it unjustified, based on the EPIC data, to give the impression that this habit could lead to such a severe illness. Perhaps the message of this EPIC publication should read: Enjoy our meat but have your veggies with it.

NOTES

Ulrike Gonder and Dr. Worm are both independent consultants and authors and have occasionally worked for the German Agriculture Marketing Board (CMA).

REFERENCES

(1) Norat T, Bingham S, Ferrari P, Slimani N, Jenab M, Mazuir M, et al. Meat, fish, and colorectal cancer risk: the European Prospective Investigation into Cancer and Nutrition. J Natl Cancer Inst 2005;97:906–16.[Abstract/Free Full Text]

(2) Gaard M, Tretli S, Loken EB. Dietary factors and risk of colon cancer: a prospective study of 50,535 young Norwegian men and women. Eur J Cancer Prev 1996;5:445–54.[ISI][Medline]

(3) Knekt P, Steineck G, Jarvinen R, Hakulinen T, Aromaa A. Intake of fried meat and risk of cancer: a follow-up study in Finland. Int J Cancer 1994;59:756–60.[ISI][Medline]

(4) Goldbohm RA, van den Brandt PA, van 't Veer P, Brandts HA, Dorant E, Sturmans F, et al. A prospective cohort study on the relation between meat consumption and the risk of colon cancer. Cancer Res 1994;54:718–23.[Abstract]

(5) Truswell AS. Meat consumption and cancer of the large bowel. Eur J Clin Nutr 2002;56 Suppl 1:S19–24.[CrossRef][ISI][Medline]

(6) Chan AT, Ma J, Tranah GJ, Giovannucci EL, Rifai N, Hunter DJ, et al. Hemochromatosis gene mutations, body iron stores, dietary iron, and risk of colorectal adenoma in women. J Natl Cancer Inst 2005;97:917–26.[Abstract/Free Full Text]

(7) de Vogel J, Jonker-Termont DS, van Lieshout EM, Katan MB, van der Meer R. Green vegetables, red meat and colon cancer: chlorophyll prevents the cytotoxic and hyperproliferative effects of haem in rat colon. Carcinogenesis 2005;26:387–93.[Abstract/Free Full Text]



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