The link between colon cancer and meat consumption has been trumpeted by vegetarians and heatedly refuted by paleo fanatics. My question, as usual, is: “What role does genetics play?”
The World Health Organization includes processed meat on their list of probable carcinogens, based on several large epidemiological studies. According to the American Cancer Society, the lifetime risk of colon cancer is around 5%, and increasing that risk by around 20% would give a lifetime risk of about 6%. But this is based just on epidemiologic studies of the population as a whole and doesn’t take into account individual genetic variants that cause addition risk — or decrease the risk.
A 2014 study looked at the interaction between genetics and the risk of colon cancer from processed meat. The study was conducted with over 9,000 people with colon cancer who were compared to 9,000 control subjects without colon cancer. The study found that the increased risk of colon cancer from meat consumption was limited to those with certain genetic variants in the GATA3 gene, a transcription factor involved in inflammation and blood vessel epithelial cells[ref].
Check your 23andMe results for rs4143094 (v.5 only):
- TT: higher risk of colon cancer with increasing meat consumption
- GT: higher risk of colon cancer with increasing meat consumption
- GG: normal
Check your 23andMe results for rs1269486 (v.4 only):
- AA: higher risk of colon cancer with increasing meat consumption
- AG: higher risk of colon cancer with increasing meat consumption
- GG: normal
The increase in the risk of colon cancer for those with the risk allele did vary by the amount of meat consumed. Those with the highest consumption of meat and a risk allele were at a 39% increased risk for colon cancer, while those with lower meat consumption were at a 20 – 26% increase in risk.
People who carry the normal genotype, which is about 60% of Caucasians and 90% of Chinese populations, were not found to have an increased risk of colon cancer with meat consumption. This actually makes sense with the population-wide studies that showed Americans to be at an 18% increased risk of cancer with meat consumption –without breaking it down by genetic differences. I think this is a great example of why dietary recommendations based on population-wide studies are often only applicable to a portion of the population.
The lifehacks here are obvious. If you carry the risk alleles (especially if you have a family history of colon cancer), cut down on the processed meats. So examples of processed meats would include brats, lunch meat, bacon, pepperoni, salami, etc. Instead, opt for some veggies along with meat or protein sources that aren’t fermented, smoked, or processed in other ways.
Finally, just for all the Parks and Recs fans who always think of Ron Swanson when they hear the word ‘meat’: