Association between red meat consumption and colon cancer: A systematic review of experimental results

Abstract

A role for red and processed meat in the development of colorectal cancer has been proposed based largely on evidence from observational studies in humans, especially in those populations consuming a westernized diet. Determination of causation specifically by red or processed meat is contingent upon identification of plausible mechanisms that lead to colorectal cancer. We conducted a systematic review of the available evidence to determine the availability of plausible mechanistic data linking red and processed meat consumption to colorectal cancer risk. Forty studies using animal models or cell cultures met specified inclusion criteria, most of which were designed to examine the role of heme iron or heterocyclic amines in relation to colon carcinogenesis. Most studies used levels of meat or meat components well in excess of those found in human diets. Although many of the experiments used semi-purified diets designed to mimic the nutrient loads in current westernized diets, most did not include potential biologically active protective compounds present in whole foods. Because of these limitations in the existing literature, there is currently insufficient evidence to confirm a mechanistic link between the intake of red meat as part of a healthy dietary pattern and colorectal cancer risk. Impact statement Current recommendations to reduce colon cancer include the reduction or elimination of red or processed meats. These recommendations are based on data from epidemiological studies conducted among cultures where meat consumption is elevated and consumption of fruits, vegetables, and whole grains are reduced. This review evaluated experimental data exploring the putative mechanisms whereby red or processed meats may contribute to colon cancer. Most studies used levels of meat or meat-derived compounds that were in excess of those in human diets, even in cultures where meat intake is elevated. Experiments where protective dietary compounds were used to mitigate the extreme levels of meat and meat-derived compounds showed protection against colon cancer, with some essentially negating the impact of meat in the diet. It is essential that better-designed studies be conducted that use relevant concentrations of meat or meat-derived compounds in complex diets representative of the foods consumed by humans.

Dietary Red and Processed Meat Intake and Markers of Adiposity and Inflammation: The Multiethnic Cohort Study

“…The 2016 IARC Working Group further concluded that the mechanistic evidence for the carcinogenicity was strong for red meat but moderate for processed meat [29]. High iron contents of red meat, particularly heme iron, meat processing resulting in formation of carcinogenic chemicals including N-nitroso-compounds (NOC) and polycyclic aromatic hydrocarbons (PAH), and the production of carcinogens such as heterocylic aromatic amines (HAA) and PAH through high-temperature cooking may account for the association between red and/or processed meat and cancer [29, 30]. However, since inflammation is a key risk factor for cancer [1], our results may suggest that red and/or processed meat consumption could also affect cancer development through the inflammatory pathway.…”

Should dietary guidelines recommend low red meat intake?

“…The interactions between meat, overall diet, human physiology (including the gut microbiome), and health outcomes are highly intricate. Within this web of complexity, and in contrast to what is commonly stated in the public domain (Leroy et al, 2018a), the current epidemiological and mechanistic data have not been able to demonstrate a consistent causal link between red meat intake and chronic diseases, such as colorectal cancer (Oostindjer et al, 2014;Turner & Lloyd, 2017). RCTs can play an important role in establishing causal relationships, and generally provide much stronger evidence than that provided by observational data.…”

“…Secondly, diets are difficult to disentangle from other lifestyle factors. It has been shown that Western-style meat eating is closely associated with nutrient-poor diets, obesity, smoking, and limited physical activity (Alexander et al, 2015;Fogelholm et al, 2015;Grosso et al, 2017;Turner & Lloyd, 2017). Given the fact that health authorities have been intensely promoting the view that meat is unhealthy, health-conscious people may be inclined to reduce intake.…”

Analysis of cancer cases from Dicle University Hospital; ten years’ experience

“…In our study, the colorectal cancer frequency was also comparable to the literature. High fat and meat consumption in the region, as well as environmental conditions, could be contributing factors [17,18].…”