Red meat and colon cancer

Does eating red meat increase your likelihood of developing colon cancer? What is the relationship between processed meat and cancer risk? In 2007, the World Cancer Research Fund and American Institute of Cancer Research issued a report stating that there was strong evidence suggesting red and processed meat influences colorectal cancer. Since then, there have been ten additional high-quality prospective studies. What does the data show? How dangerous is red, processed meat for your gut?

In the U.S. colon cancer is the third most frequently diagnosed cancer and has the second highest mortality rate. The incidence of colon cancer is much higher in countries with a "western" lifestyle and diet when compared to non-westernized countries. While this is in part due to increased screening for cancer, diet and other environmental factors are certainly at play. This is evident in "migration" studies that have shown higher rates of colon cancer among immigrants to industrialized countries when compared to matched controls.


What are "red" and "processed" meats?

For the purposes of the meta-analysis that reviewed the data, red meat consumption was described as the intake of beef, veal, pork, lamb, and mutton. Processed meat was defined as ham, bacon, sausages, cured, and preserved meats. This list isn't all-inclusive, but tried to capture the largest contributors within each category. The studies were able to quantify patients' meat intake into grams per day to assess if there was an association between the quantity of meat consumed and cancer risk. Although each study had slightly different methods of defining the quantity of meat intake, for the purposes of the meta-analysis, "high" intake was defined as at least 100 grams of red or processed meat per day. While that may sound like a lot, an average serving of red meat is 120 grams and an average serving of processed meat is 50 grams. As an example, most burger patties are 4-6 ounces, coming to 120-180 grams per patty - enough to put you well over what would be considered high intake on a given day.


What's the risk of developing colon cancer if you eat red meat?

Chan et al, PLoS One 2011. Y-axis = relative risk (i.e. 1.1 = 10% higher risk). X-axis = grams of meat per day.

Chan et al, PLoS One 2011. Y-axis = relative risk (i.e. 1.1 = 10% higher risk). X-axis = grams of meat per day.

So how did the high-intake group compare to those with low red meat consumption? Overall, risk of colon cancer was roughly 20% higher among people who ate high quantities of red meat.

That's not to say that eating less than 100 grams of red meat puts you in safe territory. The study also broke the data down to determine if there was a "dose-response" relationship, which is best quantified by the above graph that shows even a moderate amount of meat intake can moderately increase your cancer risk.

These numbers are consistent with the 2007 expert consensus, where the risk increase of colon cancer was even higher at a 29% risk increase for every 100 grams per day of red meat, and 21% risk increase for every 50 grams per day of processed meat. While the data that diet strongly influences the risk of colorectal cancer is incredibly convincing, some studies put improving food habits as way of reducing up to 70% of the colorectal cancer burden. 


How to minimize cancer risk as a non-vegetarian

A general theme of our articles is to always exercise moderation; being overly restrictive with your diet tends to be unsustainable. These numbers are meant to inform, and there are plenty of additional ways you can reduce the risk of cancer without cutting out meat entirely. While opting for plant-based alternatives is generally beneficial for your microbiome, avoiding diets high in fat, increasing your dietary fiber, getting regular exercise, and avoiding excessive alcohol intake can all help minimize your cancer risk. 


-The Gut Doc