The International Agency for Research on Cancer’s (IACR) announcement that processed meat is a cause of cancer, and that red meat is a probable cause of cancer, needs to be taken in the context of what these classifications mean, according to the Institute of Food Research.
It adds that these classifications do not indicate the size of the risk, how many cases of cancer they cause, or what sort of dose is needed.
Group 1, into which processed meat, includes tobacco smoking, alcoholic drinks, air pollution and sunlight.
Group 2A includes things which IARC believe are probably carcinogenic, but for which there is insufficient evidence to be more definitive.
Dichlorodiphenyltrichloroethane or DDT is an example of a group 2 ‘probable carcinogen’, but so are burning wood for fuel, high temperature frying, or working as a hairdresser.
IFR says the classification only relates to the quality of the available evidence, not the magnitude of the risk.
The cancer risk from tobacco is much, much higher than the risk from eating processed meat, despite reports in some of the media covering this.
Unless one is eating very large amounts on a regular basis, IFR says the increase in cancer risk is relatively very small.
IARC has concluded that the evidence in favor of an association between processed meat consumption and cancer, probably because of the ingredients used in processing, meets their criteria for placing this class of foods on the list of recognized human carcinogens.
IFR says this classification reflects the strength of the evidence for an effect, not the actual size of the risk,” says Prof. Ian Johnson, Emeritus Fellow.
“The evidence on which IARC have based their decision comes from over 800 studies, which have tended to show that people who eat more meat have slightly higher incidences of cancer, especially colorectal cancer.”
“However, these epidemiological studies cannot always rule out other confounding factors, as diet and lifestyle are very complicated.”
“We also don’t know how meat and processed meat could increase cancer risk, there are a number of possible mechanisms for this but none have definitely provided a mechanism for how meat, processed meat or compounds contained in it can trigger cancer.”
Meat consumption probably is one of many factors contributing to the high rates of bowel cancer seen in America, Western Europe and Australia, but the mechanism is poorly understood, and the effect is much smaller than, for example, that of cigarette smoking on the risk of lung cancer.
IFR says it is also worth noting that there is little or no evidence that vegetarians in the UK have a lower risk of bowel cancer than meat-eaters.
“The evidence does show a dose response, so that as the consumption of meat goes up, so does the cancer risk,” says Prof. Johnson.
“So people who are in the highest category of meat consumption (of which there are not very many) should think about reducing the amount of processed meat or red meat in their diet.”
“In the UK, current guidelines are that an adult should eat no more than 70g of red or processed meat on average each day.”
“The National Health Service choices website has more information on this recommendation as well as tips on how you can achieve this,” he adds.
“Cutting back on meat consumption, or replacing meat with fruit and vegetables, is also likely to have other health benefits, such as cutting down on salt or increasing fiber.”