The World Health Organization recently declared red meat, such as the beef in this hamburger, a probable cause of cancer. (Source: Wikimedia Commons, Bulgogi Burger, Alan Chan)
The World Health Organization (WHO) made headlines this past Monday with its press release deeming processed meat “carcinogenic to humans” and red meat “probably carcinogenic to humans” (1). This announcement was made on behalf of the International Agency for Research on Cancer (IARC), the branch of the WHO dealing with cancer.
The WHO defines red meat as referring to “all types of mammalian muscle meat, such as beef, veal, pork, lamb, mutton, horse, and goat” and processed meat as “meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation” (1). Both of these varieties are distinct from white meat, which includes turkey, chicken, and fish (2).
This story, also published in The Lancet Oncology, was based off the work of 22 cancer experts in the IARC who reviewed over 800 studies related to the link between red and processed meat and cancer (1). The experts examined data from a range of countries with varying meat-eating tendencies, and found that each 50-gram quantity of processed meat consumed daily increases an individual’s risk of colorectal cancer (also known as bowel or colon cancer) by 18% (1).Weaker associations have been observed for pancreatic and prostate cancer, but colorectal cancer presented the largest threat (1).
The scientists also emphasized that the carcinogenic implications were most threatening for those who frequently eat large portions of meat. Dr. Kurt Straif, Head of the IARC Monographs Programme, stated that “the risk of developing colorectal cancer because of…consumption of processed meat remains small, but this risk increases with the amount of red meat consumed” (1).
Although a large amount of research has been devoted to this area of study, what makes red and processed meat carcinogenic is still unclear. The main theory states that red and processed meats form toxic chemicals called N-nitroso compounds that damage the cells lining the bowel (2). The remaining cells in the bowel lining respond by replicating more frequently, and the additional replication can lead to genetic errors and the creation of cancerous genes (2).
In red meat, N-nitroso compounds are generated when the chemical heme (found in the hemoglobin of the blood) is broken down (2). On the other hand, processed meats contain chemicals, like nitrite preservatives, that are precursors to N-nitroso compounds (2).
Despite the apparent lack of understanding regarding the exact science behind these carcinogenic effects, the IARC has declared processed meat as “definitely carcinogenic,” and red meat as “probably carcinogenic”: These classifications rate how confident scientists are about the carcinogenic potential of certain items, as opposed to the degree of carcinogenicity (2). This places, processed meat in the same category as alcohol and cigarettes, and red meat with factors like shift work (2).
However, scientists like Dr. Christopher Wild, Director of IARC, emphasize that “red meat has nutritional value. Therefore, these results are important…in order to balance the risks and benefits of eating red meat and processed meat” (1). The exact nature of this balance remains to be determined.
References:
1. International Agency for Research on Cancer. (2015, October 26). IARC Monographs Evaluate Consumption Of Red Meat And Processed Meat. Retrieved from http://www.iarc.fr/en/media-centre/pr/2015/pdfs/pr240_E.pdf
2.Dunlop, C. (2015, October 26). Processed meat and cancer – what you need to know. Retrieved October 31, 2015, from http://scienceblog.cancerresearchuk.org/2015/10/26/processed-meat-and-cancer-what-you-need-to-know/