The EU wide research that spanned ten countries and tracked nearly half a million consumers concluded colorectal risk increases by 49 per cent per 100 grams of daily consumed red meat, to cover pork, beef, veal, and lamb.
By contrast, their findings suggest that high fish intake may reduce the risk, although "existing evidence is less convincing," write the researchers.
This latest study builds on accumulating research, first published in 1990, that indicate the link, although with nearly 500,000 participants, this is one of the largest cohorts of men and women to examine the relationship between diet and cancer.
"The absolute risk of developing colorectal cancer within ten years for a study subject aged 50 years was 1.71 per cent for the highest category of red meat intake and 1.28 per cent for the lowest category," report the researchers based in academic institutions across Europe, from Lyon in France to German Cancer Research Center in Heidelberg.
These figures, write the study authors, take account of the influence of different factors such as gender, body weight, alcohol comsumption, physical exercise or smoking on the disease risk.
Defending its industry, the American Meat Institute Foundation immediately rejected the study and its findings, accusing the study of being epidemiological, " which means it does not prove cause," the industry body said in a statement yesterday.
The group claims the study's relative risk of 1.71 should be viewed with 'sceptism', and quotes the epidemiologist Ernst Wynder who, in the American Journal of Epidemiology in 1986, said relative risks under 3.0 are suspect.
"We should not rush to judgment about a causative implication when in fact the word 'association' ought to be used," said Wynder.
The most important fact is that the larger body of evidence has shown processed meats are a healthy part of a balanced diet, added the American Meat Institute Foundation yesterday.
But researchers working on the European Prospective Investigation into Cancer and Nutrition (EPIC) claim the analysis is based on 1.329 cases of rectal and colon cancer that have been newly diagnosed among participants since the study begun.
"Study subjects who had eaten a lot of what is called "red" meat, or such meat products, were diagnosed with colorectal cancer more often than persons who ate only little of it," they report in the 15 June issue of the Journal of the National Cancer Institute.
People who eat diets rich in meat also tend to eat less fibre and less fish, they add.
Those who ate a lot of fish were found to have a significantly lower colorectal cancer risk compared to those with a low fish consumption. The consumption of poultry played no role for colorectal cancer incidence, they write.
Looking into the reasons behind their findings, the scientists propose different explanations: recent studies suggest that the intake of iron contained in meat may contribute to risk elevation, because iron can promote the formation of harmful nitroso compounds in the body.
On average, red meat or meat products have a higher iron content than poultry, which may explain why consumption of the latter may not have influenced colorectal cancer risk in this study.
The protective effect of fish consumption may be caused by specific long chain, polyunsaturated omega-3 fatty acids.