A report released this morning by an international team of researchers says there’s convincing evidence that eating too much red meat and processed meat raises colorectal cancer risk and that consuming plenty of fiber in the form of plant-based foods reduces that risk.
The World Cancer Research Fund and American Institute for Cancer Research together produce the Continuous Update Project (CUP), which gathers research about various forms of cancer, updating its database every few years. For this report, scientists at Imperial College London conducted a review of published studies and ended up adding 263 new papers about colorectal cancer to the 749 that had been analyzed for the last report, issued in 2007. After that, an expert panel analyzed all the collected evidence regarding the relationships between diet, weight and physical activity and colorectal cancer.
The report notes that there is “convincing evidence” that:
l Red meat, processed meat, excess body fat and fat carried around the waist increase risk of colorectal cancer.
l Regular physical activity reduces risk of colorectal cancer.
l Foods containing dietary fiber, such as fruits, vegetables, whole grains and beans, reduce risk of colorectal cancer; garlic probably does, too (though the evidence for this isn’t as strong).
l Alcohol increases colorectal cancer risk in men. For women, it probably increases risk.
The report further finds that milk probably reduces colorectal cancer risk (but’s not clear how milk consumption affects overall risk) and that dietary supplements containing calcium probably reduce cancer risk, but in general it’s best to get such nutrients from foods, not supplements.
The news release announcing the report’s publication notes that:
Red meat refers to beef, pork and lamb. If a person eats 3.5 ounces of red meat every day (24.5 ounces per week), their risk of colorectal cancer will be 17% higher than someone who eats no red meat. If they eat 7.0 ounces of red meat every day (49 ounces per week), their risk will be 34% higher, and so on. The evidence shows that there is very little increase in risk for people who keep their intake of red meat to less than 18 ounces a week.
Processed meat is meat preserved by smoking, curing, salting or by the addition of preservatives. Examples include ham, bacon, pastrami and salami, as well as hot dogs and sausages. If a person eats 3.5 ounces of processed meat every day (24.5 ounces per week), their risk of colorectal cancer will be 36% higher than someone who eats no processed meat. If they eat 7.0 ounces of processed meat every day (49 ounces per week), their risk will be 72% higher.
According to the Centers for Disease Control and Prevention, among cancers affecting both men and women, colorectal cancer is the second leading cause of cancer death in the United States. Of 142,672 people diagnosed with the disease in 2007, 53,219 people died from it.