Meat consumption, particularly of red and processed meat, is one of the most thoroughly studied dietary factors in relation to colon cancer.
Scientists led by Maureen Murtaugh at the University of Utah set out to decipher whether meat, red meat, HCAs or PAHs are associated with the risk for rectal cancer. Their findings suggest that 'mutagens' such as HCA that form when meat is cooked may be the risk factor in rectal cancer, not red meat itself.
PAHs and HCAs are known carcinogens which can form as a by-product of reactions occurring during the cooking of meat, particularly if it is fried, broiled, baked or barbecued.
The team at Utah studied 952 subjects with rectal cancer and 1,205 controls, from Utah and California in a population-based case-control study from 1997-2002. Medical history and dietary habits and other exposure data were recorded. Blood was taken from the participants, DNA extracted and variants of NAT2 were recorded.
Their findings revealed a slight non-significant increase in risk of rectal cancer among men and women with the highest consumption of processed meat or 'well done meat. Men who had the rapid or intermediate acetylator phenotype and consumed well done meat had a greater increase in the risk for rectal cancer than men with the slow acetylator-imputed phenotype. In women, the use of red meat drippings was associated with a decreased risk of rectal cancers. This decrease was greater among women with the slow NAT2 imputed phenotype and the GSTM-1 absent genotype.
According to the World Heath Organisation, colorectal cancer is among the five most common cancers in the world for both men and women. More than 10 million people are diagnosed with cancer every year and WHO estimates that there will be 15 million new cases every year by 2020. Cancer causes 6 million deaths every year - or 12 per cent of deaths worldwide.
Despite recent food safety scares, notably BSE and avian flu, meat consumption remains steady. Even the recent BSE scare in the US has not affected the popularity of meat as a meal choice. Consumption has been boosted by the popularity of the low-carb Atkins diet, which encourages the consumption of protein. An estimated 59 million adults in the US are currently on the diet, according to figures from the Valen Group, and are turning to meat, a relatively cheap and easibly available source of protein.
Full findings of the Utahstudy are published in the The American Society for Nutritional Sciences, J. Nutr. 134:776-784, April 2004.