Recent headlines have touted that meat consumption causes colon cancer. Of course, this has set off Twitter wars between meat lovers and vegetarians, with most people left wondering how this personally affects them. Should they eliminate red meat from their diet? What is the true risk of colon cancer due to meat consumption?
Colon cancer, red meat, and personalized nutrition:
In 2015, the World Health Organization included processed meat (e.g., sausages, ham, hot dogs, beef jerky) on its list of probable carcinogens.[ref] The listing is based on several large epidemiological studies that show processed meat consumption increases the relative risk of colon cancer by 18-20%.
For example, a meta-analysis combining data from 42 studies determined that consuming processed meat increased colon cancer risk by 20%.[ref]
Putting the risk into perspective:
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%.[ref]
Importantly, this statistical risk is based on epidemiological studies of the population as a whole. It doesn’t take into account individual genetic variants that can increase – or decrease – the risk of colon cancer.
When you bring individual genetics into the picture, it turns out that for some people, meat consumption probably doesn’t increase the risk of colon cancer at all. For other people, the increase in risk is quite a bit higher than the 20% increase.
Genetics and colon cancer risk:
A 2014 study looked at the interaction between genetics and the risk of colon cancer from processed meat intake. Researchers examined the genes of 9,000 colon cancer patients and 9,000 control subjects without colon cancer. They discovered a significant diet-gene interaction between the GATA3 gene variants and colon cancer risk when stratified by meat consumption (processed meat and red meat).[ref]
Another study found that a genetic variant in the CCAT gene normally decreased the risk of colon cancer, but in conjunction with a high intake of processed meat, that protection was eliminated. [ref]
Polyps and meat intake:
Colorectal polyps are often precursors for colon cancer. These are the growths that doctors remove when you get a colonoscopy done in order to prevent cancer. Not all polyps go on to become cancerous, but polypectomy is a well-studied prevention method.
Red meat intake is associated with polyps, and genetic variants impact whether red meat is likely to cause you to have polyps. The aryl hydrocarbon receptor (AhR) is an important detector of toxicants, such as polycyclic aromatic hydrocarbons from high-temperature meat cooking. Polycyclic aromatic hydrocarbons are linked to the DNA changes that can cause benign polyps and malignant tumors.[ref]
Colon Cancer and Meat Genotype Report:
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GATA3 Genetic Variants:
Researchers discovered the increase in colon cancer was linked to the GATA3 gene. This gene codes for a transcription factor involved in inflammation in the epithelial cells that line your blood vessels.
High processed meat consumption in people with certain GATA3 genetic variants increased colon cancer cases significantly.[ref]
Check your genetic data for rs4143094 (23andMe v5; AncestryDNA):
- T/T: higher risk of colon cancer with increasing meat consumption (~40% increased relative risk)
- G/T: higher risk of colon cancer with increasing meat consumption (~20% increased relative risk)
- G/G: typical (no increased risk of colon cancer with processed meat consumption)
Members: Your genotype for rs4143094 is —.
Check your genetic data for rs1269486 (23andMe v4; AncestryDNA):
- A/A: higher risk of colon cancer with increasing meat consumption
- A/G: higher risk of colon cancer with increasing meat consumption
- G/G: typical (no increased risk of colon cancer with processed meat consumption)
Members: Your genotype for rs1269486 is —.
Doing the math:
The increase in the risk of colon cancer for those with the risk allele did vary by the amount of meat consumed. Carriers of the risk allele who ate the highest percentage of meat had a 39% increased risk for colon cancer; carriers who ate less meat were at a 20 – 26% increase in risk.
People who carry the typical genotype, about 60% of Caucasians and 90% of Chinese populations, were not found to have an increased risk of colon cancer with meat consumption.
Statistically, this makes sense with the population-wide studies that showed Americans overall at an 18% increased risk of cancer with meat consumption. It illustrates why population-wide recommendations for the diet are often misleading for an individual.
CCAT genetic variants:
Another study on the link between colon cancer and processed meat consumption found that the CCAT genetic variant also comes into play with meat consumption and colon cancer.
In general, carrying the rs6983267 T-allele is associated with a lower risk of colon cancer, and this protection is further enhanced by the regular use of aspirin.[ref][ref] But, when looking at processed meat consumption of over 25 g/day, that protection in the risk for T-allele carriers was eliminated.[ref]
It is a case where dietary choices eliminate natural genetic protection against colon cancer.
Check your genetic data for rs6983267 (23andMe v4, v5; AncestryDNA):
- G/G: normal (higher) risk of colon cancer
- G/T: somewhat decreased risk of colon cancer — except for people who eat a lot of processed meat
- T/T: generally a decreased risk of colon cancer — except for people who eat a lot of processed meat[ref]
Members: Your genotype for rs6983267 is —.
Aryl Hydrocarbon Receptor Variant
AHR gene: encodes the aryl hydrocarbon receptor, important in detecting polycyclic aromatic hydrocarbons in cooked meat.
Check your genetic data for rs2066853 (23andMe v4; AncestryDNA):
- G/G: typical
- A/G: increased risk of colorectal polyps with high meat intake
- A/A: increased risk of colorectal polyps with high meat intake[ref]
Members: Your genotype for rs2066853 is —.
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Originally published 1/2018; updated 8/2020