The meat-colorectal cancer correlation was first elucidated in a report by the International Agency for Research on Cancer (IARC) in 2015.
The Korean researchers carried out a thorough review of over 500 studies that had previously been conducted on meat consumption and cancer.
These included cohort and case-control analyses, prospective and retrospective studies, other review articles, as well as IARC monograph reports.
Of these, 73 human epidemiological studies were selected for more in-depth analysis.
“The aim was to investigate the relationship between meat intake and colorectal cancer risk from an Asian, particularly Korean, perspective,” said the authors.
“[We found] that approximately 76% [of the studies] were conducted in Western countries, whereas only 15% of studies were conducted in Asia. Furthermore, most studies conducted in Asia showed that processed meat consumption is not related to the onset of cancer.”
“[As such], the correlation between intake of processed meat products and colorectal cancer incidence in Asians is not clearly supported,” they concluded.
The study also reported that there do not exist any conclusive reports proving a significant correlation between meat consumption and colorectal cancer, whether it involves processed meats, raw meats or the relevant cooking methods.
The IARC 2015 study
The original IARC 2015 study had stated that “each 50 gram portion of processed meat or 100 grams daily of red meat eaten daily increases the risk of colorectal cancer by 18% and 17% respectively”.
This was according to a literature review by 22 experts from 10 countries, convened via the IARC Monographs Programme.
The official classification of red meat consumption was Group 2A – Probably carcinogenic to humans.
“[This is] based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect,” said the IARC in a statement.
Colorectal cancer was the main associated cancer type, but pancreatic and prostate cancers were also mentioned.
IARC Monographs Programme Head Dr Kurt Straif said: “For an individual, the risk of developing colorectal cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed.”
“In view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance.”
The recommendation at the time was to limit meat intake to avoid carcinogenic effects.
“These findings further support current public health recommendations to limit intake of meat,” said Dr Christopher Wild, Director of IARC.”
The IARC defines red meat as ‘all mammalian muscle meat, including, beef, veal, pork, lamb, mutton, horse, and goat’. Processed meat is defined as ‘meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation’.
The feedback to this recent discovery has been less than positive for the IARC and World Health Organisation (WHO) as a whole.
Online comments vary from it being ‘not really surprising [as] the correlation from the WHO was very weak as it was’ to ‘the WHO overstepped [with their IARC report]’.
The IARC is part of the WHO, with a mandate to conduct and coordinate research into the causes of cancer.
That said, the study authors are urging for more culturally sensitive research to be conducted before any conclusions are drawn about meat and cancer.
“Further epidemiological studies taking each country’s food culture into consideration are required to reliably elucidate the effects of processed meat product intake, especially on cancer incidence,” the authors concluded.
Source: Critical Reviews in Food Science and Nutrition
Controversy on the correlation of red and processed meat consumption with colorectal cancer risk: an Asian perspective
Authors: Hur, S.J. et. al.