Regularly eating red meat and processed meat such as bacon, sausages, ham and burgers increases the risk of developing bowel cancer, researchers said.
A European study involving nearly half a million adults showed those who eat more than two portions of red or processed meat a day increase their risk by a third compared with those who eat very little.
Those who eat fish every other day reduce their risk by nearly a third compared with people who eat fish less than once a week. Regular poultry eaters are neither at an advantage or disadvantage.
The European Prospective Investigation into Cancer and Nutrition (Epic) says that those who eat red or processed meat regularly but with little fiber -- from vegetables and whole grains -- increase their risk even more.
Doctors increasingly believe that two thirds of bowel cancers could be prevented by changes in diet and lifestyle. The results confirm what they have been saying for some time, but much of the evidence has been circumstantial.
For the purposes of the study, published in the Journal of the National Cancer Institute, red meat included beef, pork, lamb and veal. The increased risk of a third is for those who eat 160g (5.6oz) or more of red meat a day, compared with people who eat less than 20g a week.
Sheila Bingham, from the Medical Research Council Dunn Nutrition Unit, Cambridge, a lead investigator in the study, said the overall picture was "very consistent for red and processed meat and fiber across Europe." She said that the incidence of bowel cancer among Japanese had risen sharply since they began to adopt a Western diet.
In the study, 478,040 men and women in 10 European countries, including Britain, were enrolled between 1992 and 1998 and followed for an average of five years. In that time, 1,329 colon or rectal cancers bowel were diagnosed.
Factors such as smoking, obesity and heavy drinking, which also affect the incidence of bowel cancer, were taken into account.
Tim Key, the deputy director of the epidemiology unit at Cancer Research U.K., which also took part in the study, said it strengthened the evidence that the risk of bowel cancer could be cut by increasing fiber in the diet and reducing the amount of red meat eaten.
"Around 35,000 cases of bowel cancer are diagnosed each year in the United Kingdom. We estimate that more than two thirds of those -- 25,000 cases -- could be avoided by changes in lifestyle," he said.
John Bullock, the spokesman for the Meat and Livestock Commission, said, "Consumption of 160g a day is high. Average consumption in Britain is 93g.
"Our view has always been that we should aim for balance in what we eat.
"Typically, we eat meat with vegetables and potatoes, providing the fiber that has a protective effect against bowel cancer."
The U.K.’s Food Standards Agency said red meat was recommended as part of a healthy diet, as it was a "good source of iron and other minerals and vitamins," but due to the saturated fat content, it should be eaten in moderation.
