The American Institute for Cancer Research describes processed meat as “meat preserved by smoking, curing, or salting, or addition of chemical preservatives.” Some examples of processed meats include bacon, ham, sausage, deli meats, and hot dogs. A study by the Harvard School of Public Health in 2010-12, concluded that even small portions of processed meat consumed on a regular basis has a significant correlation with an increased risk of colorectal cancer, cancer mortality, and cardiovascular disease.

The causal link between an increased risk for colorectal cancer and regular processed meat consumption is not yet defined; nevertheless, several mechanisms are being currently researched. Nitrates are usually added to processed meats to preserve their color or to prevent them from spoiling. It has been found through research studies that these nitrate compounds form cancer-causing compounds called carcinogens. Smoked, processed meats contain a substance called PAH, or polycystic aromatic hydrocarbon, which are produced with high temperatures and can cause cancer. Meat that is cooked at a high temperature may also contain PAH, as well as heterocyclic amines (HCAs). These substances are known to damage DNA.

In 2007, an American Institute for Cancer Research (AICR) publication on food, nutrition, and cancer prevention stated that processed meat could possibly increase the risk for cancers affecting several parts of the body such as colorectum, endometrium, esophagus, lung, pancreas, prostate, and the stomach. Further, the research study said that scientific evidence against processed meat was very strong, with respect to colorectal cancer risk. In Cancer Prevention Study II, involving 148,610 adults (conducted from 1982), the risk for colon cancer was as high as 50% in individuals who consumed hams, hot dogs, bacon, sausage, etc.

An article in the Journal of Human Nutrition and Dietetics, published in 2009, stated that there was a definite correlation between prostate cancer and highly processed or charcoaled meats. A study in the British Journal of Cancer in 2011 on meat consumption reported that 25% of bowel cancer in men and about 17% in women were related to the consumption of red meat or processed meat.

The (US) Physicians Committee for Responsible Medicine explains that processed meat is generally lacking in the much needed minerals and nutrients, antioxidants, and phytochemicals that protect and fight for the body. Also, such meats contain high fat and salt content, along with certain potentially carcinogenic substances, resulting in an overall increased risk for cancer. Lately, the World Cancer Research Fund (WCRF), in their recommendations, have advised that eating processed meat be completely avoided.

References:

Ma RW, Chapman K. A systematic review of the effect of diet in prostate cancer prevention and treatment. J Hum Nutr Diet. 2009;22(3):187-1899; quiz 200-202. Epub 2009 Apr 1.

Parkin DM (2011e). Cancers attributable to dietary factors in the UK in 2010. II Meat consumption. Br J Cancer105 (S2):S24-S26.

FAQ: Processed Meat and Cancer [Internet]. 2014 Aug 7. [cited 2014 Oct 30]. Available from: http://www.aicr.org/enews/2014/08-august/faq-processed-meat-and.html 

http://www.cancer.gov/cancertopics/factsheet/Risk/cooked-meats (accessed on 12/02/2014)

http://www.pcrm.org/health/cancer-resources/diet-cancer/facts/meat-consumption-and-cancer-risk (accessed on 12/02/2014)

http://www.cancerresearchuk.org/cancer-info/healthyliving/diet-healthy-eating-and-cancer/stats-evidence/diet-and-cancer-the-evidence#Meat (accessed on 12/02/2014)

http://www.nhs.uk/Livewell/Goodfood/Pages/red-meat.aspx (accessed on 12/02/2014)

Helpful Peer-Reviewed Medical Articles:

Cross, A. J., Leitzmann, M. F., Gail, M. H., Hollenbeck, A. R., Schatzkin, A., & Sinha, R. (2007). A prospective study of red and processed meat intake in relation to cancer risk. PLoS Med, 4(12), e325.

Chan, D. S., Lau, R., Aune, D., Vieira, R., Greenwood, D. C., Kampman, E., & Norat, T. (2011). Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies. PloS one, 6(6), e20456.

Santarelli, R. L., Pierre, F., & Corpet, D. E. (2008). Processed meat and colorectal cancer: a review of epidemiologic and experimental evidence.Nutrition and cancer, 60(2), 131-144.

Larsson, S. C., & Wolk, A. (2012). Red and processed meat consumption and risk of pancreatic cancer: meta-analysis of prospective studies. British journal of cancer, 106(3), 603-607.

Larsson, S. C., Orsini, N., & Wolk, A. (2006). Processed meat consumption and stomach cancer risk: a meta-analysis. Journal of the National Cancer Institute, 98(15), 1078-1087.

Chao, A., Thun, M. J., Connell, C. J., McCullough, M. L., Jacobs, E. J., Flanders, W. D., ... & Calle, E. E. (2005). Meat consumption and risk of colorectal cancer. Jama, 293(2), 172-182.

Larsson, S. C., Bergkvist, L., & Wolk, A. (2006). Processed meat consumption, dietary nitrosamines and stomach cancer risk in a cohort of Swedish women. International journal of cancer, 119(4), 915-919.

Alexander, D. D., Mink, P. J., Cushing, C. A., & Sceurman, B. (2010). A review and meta-analysis of prospective studies of red and processed meat intake and prostate cancer. Nutrition journal, 9(1), 1.