All things in moderation: Consuming excessive quantities of red meat, such as filet mignon steaks (pictured), may increase your risk of developing a range of cancers.

Credit: iStockphoto

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SYDNEY: Eating too much red and processed meat can increase your risk of developing a range of cancers, says a detailed eight-year study of nearly half a million people.

The study, which is the first to assess the overall risk from meat of developing a range of cancers, found that the people surveyed who ate the most were up to 60 per cent more likely to develop some types of cancer than those who ate the least.

"A particular strength of this study includes the large size of the cohort, which enabled us to investigate low-incidence cancers that have not previously been [assessed]," write the authors in the journal PLoS Medicine.

Lifestyle study

To overcome the limitations of previous studies which have tested small numbers of people or collected data over shorter time frames, the epidemiologists led by Amanda Cross at the U.S. National Institutes of Health in Rockville, Maryland, recruited 494,000 people and collected data on many aspects of their lifestyle.

The study population consisted of men and women, aged between 50 and 71, none of whom had previously had cancer. In this study, red meat was classed as beef, pork or lamb.

The researchers compared the 20 per cent of participants who consumed the most meat to the 20 per cent who consumed the least. Statistical analysis of the data for red meat showed a 20 to 60 per cent increased risk of developing colorectal, liver, lung, and oesophageal cancers. A diet rich in processed meat was associated with a 20 per cent elevated risk for colorectal and a 16 per cent elevated risk for lung cancer.

The study controlled for the influence of a number of other lifestyle factors, which might also increase the risk of developing cancer, such as smoking.

Cross and her team suggest that certain carcinogenic compounds in meat – including N-nitroso compounds, heterocyclic amines, and polycyclic aromatic hydrocarbons – could be linked to the increased rates of cancer.

Preparation method

"There is no doubt there is a link between colorectal cancer and red meat, there are now over 20 studies all showing a similar risk," commented Peter Clifton, director of the Nutrition Clinic of Australian government research body, the CSIRO.

Ian Olver, with the Cancer Council Australia, in Sydney, points out that one limitation of the study is the lack of information about how the meat was prepared.

"With meat there are probably three things that are important," he said. "One is just the fat content of the meat, because we know that fat is associated with cancer. The second is how you cook the meat, because clearly if you barbeque the meat there will be more carcinogens than a slow cooked type of meat. And the third is how you preserve the meat; for example in southeast Asia where it is common to salt or smoke meat, we know you get carcinogens produced by those processes."

Another limitation of the study is that it didn't quantify how much meat the people in the highest consumption category where eating. It does however benefit from having a huge number of participants, Olver said.

Other studies have shown that eating fish decreases the risk of developing colorectal cancers, while the risks from white meats, such as chicken, appear to be lower. Overall, dietary factors are thought to contribute to around 35 per cent of cancers.