Cancer and red meat
The International Agency for Research on Cancer (IARC) is part of the WHO with a mission to coordinate and conduct research on the causes of human cancer, the mechanisms of carcinogenesis, and to develop scientific strategies for cancer control. They have developed a system of categories to evaluate the carcinogenicity of different agents, including foods, to humans.
Agents which fall within Group 1 are labelled Carcinogenic to humans. This grouping is made based on sufficient evidence of carcinogenicity, or sufficient evidence of carcinogenicity in experimental animals and strong evidence in exposed humans that the agent acts through a relevant mechanism of carcinogenicity. A total of 111 agents have been classified within this group.
Group 2A classifies agents as Probably carcinogenic to humans. This classification is made if sufficient evidence of carcinogenicity in experimental animals is available and strong evidence that the carcinogenesis is mediated by a mechanism that also operates in humans, or if there are limited evidence of carcinogenicity in humans, but the agent belongs, based on mechanistic considerations, to a class of agents for which one or more members have been classified in Group 1 or Group 2A. A total of 66 agents have been grouped in this category.
Group 2B classifies agents as Possibly carcinogenic to humans. Agents are classified within this group if there is limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals, or there is inadequate evidence of carcinogenicity in humans but sufficient evidence of carcinogenicity in experimental animals, or if there is supporting evidence from mechanistic and other relevant data. A total of 285 agents have been grouped into this category.
Group 3 is used to group agents which are Not classifiable as to its carcinogenicity to humans. Agents are applied within this group if the evidence of carcinogenicity is inadequate in humans and in experimental animals, or if sufficient in experimental animals, there is no evidence that the mechanism of carcinogenicity in experimental animals does operate in humans. This group is also used when agents do not fall into any other group. Agents in Group 3 are not determined to be non-carcinogenic or safe, but rather mean that further research is needed. 505 agents have been grouped in this category.
Group 4, namely Probably not carcinogenic to humans, is used when evidence suggest lack of carcinogenicity in humans and in experimental animals. Of the 968 agents evaluated by the IARC, only 1 agent has been grouped into this category. This agent, caprolactam, is the precursor to Nylon.
On 26 October 2015, the IARC published a summary of their evaluation of red and processed meat in the British Medical journal The Lancet Oncology, and the World Health Organization (WHO) Press Release No 240 swiftly followed.
The report concluded that the consumption of red meat is probably carcinogenic to humans (Group 2A), and the consumption of processed meat is carcinogenic to humans (Group 1).
Cancer risk in South Africa
According to the 2010 release of the National Health Laboratory Service (NHLS) the cumulative lifetime incidence risk for cancer of a South African male is 12.77%, which means 1 in every 7 men will get some form of cancer, at some point during their lifetime. For a South African female, the risk is 10.95%. This means that 1 in every 9 women will get cancer. For men, skin cancer is the most prevalent, followed by prostate cancer. Colorectal cancer is the 7th most common cancer in South African men with a lifetime risk of 0.88%, or 1 in 114. In South African women, breast cancer is the most prevalent, followed by cervical cancer and skin cancer. Colorectal cancer is the 6th most prevalent cancer in women, with a lifetime risk of 0.55%, or 1 in 182.
What we need to understand from the IARC Red and processed meat evaluation
- The evaluation did not introduce any new evidence and was based on a review of existing scientific literature.
- The IARC represents the opinion of a selected group of scientists and this opinion is not based on consensus in the global scientific community.
- No group member was from a developing country, and no study from the African continent was included in the red and processed meat review.
- The evaluation involved a hazard analysis, not a risk assessment. This distinction is important. It means that the panel members considered whether processed meat and red meat at some level, under some circumstance, could be a hazard. The fact that it did not include a risk assessment means that it did not take into account the real quantifiable exposure to the substance linked to its potential to cause cancer.
- Despite not conducting a risk assessment, the report continued to publish a risk, namely that eating 50 grams of processed meat each day can increase the risk of colorectal cancer by 18%.
- The final classifications for the 2015 report were based on a majority agreement, and not on unanimous consensus of all members of the working group.
How the report affects South Africans
- Food culture of people differs around the world. The majority of South Africans consume mostly chicken, then beef, followed by pork, lamb or mutton and then processed meat (BFAP, 2015).
- Our processed meat looks significantly different to processed meats found in other countries, i.e. in most viennas, polonies and even fresh wors, the main ingredient is often not derived from red meat, but vegetable proteins and mechanically deboned chicken.
- South Africans in fact consume a low level of processed meat, at an average of 12g per person, per day.
- If a South African does decide to consume more than 50g processed meat each day, the report states an 18% increase risk for colorectal cancer. The normal lifetime risk for developing colorectal cancer in South Africa is 0.88% for men, and 0.55% for women. Increasing this risk by 18%, means your risk of getting colorectal cancer will increase to 1.04% for a male, and 0.65% for a female - remaining a relatively low risk.
- No quantifiable risk for the consumption of fresh red meat was published in the report. Despite being a meat-loving nation, South Africans consume less red meat than what is often perceived. On average South Africans eat notably less protein-source foods (11 to 18%) compared to recommended levels by the World Health Organisation (WHO) which state that 20% of total dietary energy should be from protein (Mchiza et al., 2015).
- Food energy of South Africans are mainly derived from carbohydrates such as maize meal and bread (between 57% and 69%) (Mchiza et al., 2015), which is significantly higher than the recommended 45%. This may be more linked to affordability than to choice.
- Cancer is a multi-complex problem that cannot be solved or blamed on one specific product or food group. The best way to minimize your cancer risk is to live a healthy lifestyle, including:
- Do not smoke
- Maintain a healthy weight
- Enjoy regular physical activity
- Accompany red meat with plenty of vegetables and whole grains
- If you do drink alcohol, drink responsibly
- Enjoy red and processed meat as recommended in our Food-Based Dietary Guidelines:
- Eat a variety of food
- Fish, chicken, lean meat or eggs could be eaten daily
- Consume up to 90g cooked, lean meat daily.
- Be a conscientious cook:
- Stay by the grill or barbecue and flip the meat more often to avoid overcooking and possible charring of the meat surface.
- Avoid direct exposure of the meat to an open flame.
- Panfry red and processed meat over medium versus high heat.
- Marinate meat in marinades containing citrus juices like lemon or lime and add spices such as garlic or onion.
International Agency for Research on Cancer. Agents classified by the IARC monographs, volumes 1-108. Available from: http://monographs.iarc.fr/ENG/Classification/index.php.
National Health Services Laboratory. National Institute for Occupational Health. National Cancer Registry. 2010. Report available online at: http://www.nioh.ac.za/assets/files/NCR_Final_2010_tables(1).pdf
BFAP. Bureau of Food and Agtricultural Policy. 2015. Baseline Report. Report available online at: http://www.bfap.co.za/index.php/research-projects/baselines
Mchiza, ZJ, Steyn, NP, Hill, J, Kruger, A, Nel, J, Schonfeldt, H & Wentzel-Viljoen, E 2015, 'A review of dietary surveys in the adult South African population from 2000-2015', Nutrients.
Article prepared by: Schönfeldt, H.C. & Hall, N (2016-2)
Institute of Food, Nutrition & Well-being, University of Pretoria, Pretoria, South Africa. HCS Health Communication: Food and Nutrition Research & Communication (email@example.com)