Speaking at the American Society of Human Genetics 2013, the researchers behind the discovery revealed how they systematically searched the more than 2.7 million genetic sequences for interactions with consumption of red and processed meat - finding that the risk of colorectal cancer associated with processed meat was significantly higher among people with a specific genetic variant known as 'rs4143094'.
This genetic variant is found in around 36% of the population, said the research team.
In addition to identifying a gene that raises risk for the cancer from eating red or processed meat, the study — which is the first to identify the interactions of genes and diet on a genome-wide scale — also revealed another specific genetic variation that appears to modify whether eating more vegetables, fruits and fibre lowers colorectal cancer risk.
"Diet is a modifiable risk factor for colorectal cancer," explained Dr Jane Figueiredo from the University of Southern California. "Our study is the first to understand whether some individuals are at higher or lower risk based on their genomic profile."
"If replicated, our findings have a relevant public health significance because diet is a modifiable risk factor for colorectal cancer," Figueiredo added, suggesting that it is 'conceivable' that people who are identified as having a higher risk of colorectal cancer based on genomic profiling could be targeted for screening, diet modification and other prevention strategies."
"But we are not saying that if you don't have the genetic variant that you should eat all the red meat you'd like," Figueiredo cautioned. "People with the genetic variant allele have an even higher increased risk of colorectal cancer if they consume high levels of processed meat, but the baseline risk associated with meat is already pretty bad."
The new study is the first colorectal cancer investigation with the statistical power to identify gene-dietary interactions across the genome of a large population of individuals - with the team analysing data from 9,287 patients with colorectal cancer and a control group of 9,117 individuals without cancer.
Ulrike Peters, senior author of the study, noted that the possibility that genetic variants may modify an individual's risk for disease based on diet has not been thoroughly investigated but represents an important new insight into disease development.
The team systematically searched 2.7 million variants to identify those that are associated with the consumption of red meat and processed meat as well as fruits and vegetables - finding a significant interaction between the genetic variant rs4143094 and processed meat consumption.
But other genetic variants may be beneficial, they said. On chromosome 8, another statistically significant diet-gene interaction was found in variant rs1269486. For people with this variant, eating your fruits and vegetables may be even better for you when it comes to colorectal cancer risk, the team said.
How specific foods affect the activities of genes has not been established, however the team speculated that digestion of processed meat may promote an immunological or inflammatory response that may trigger tumour development.
"Colorectal cancer is a disease that is strongly influenced by certain types of diets," Figueiredo said. "We're showing the biological underpinnings of these correlations, and understand whether genetic variation may make some people more or less susceptible to certain carcinogens in food, which may have future important implications for prevention and population health."