One in three people is born with a gene that significantly increases their likelihood of developing bowel cancer from eating processed meat, a study has found.
Compared with those eating little or no processed meat, the heaviest consumers were more than twice at risk of the disease if they had the worst version of the gene variant.
Eating meat - especially processed meat in pies, bacon, sausages and cold cuts - was already known to raise bowel cancer risk, but the gene mutations increase it even more.
"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," said Dr Li Hsu, one of the study authors from the Fred Hutchinson Cancer Research Center in Seattle, US.
The scientists analysed data collected from 10 diet and health studies involving more than 18,000 participants.
Pooling information in this fashion can reveal trends that would otherwise remain hidden.
The study divided people into four groups with increasing levels of meat consumption up to around five servings per week.
Compared with the first group, each subsequent "quartile" of higher consumption of processed meat raised the risk of bowel cancer by 39% for individuals with the most hazardous mutation.
Another version of the rs4143094 gene variant increased the risk by 20% per quartile.
In contrast, vegetable, fruit and fibre intake was associated with a slightly reduced risk overall.
Writing in the online journal Public Library of Science Genetics, the researchers point out that rs4143094 is in the same chromosomal region as a gene known to be linked to several forms of cancer.
The protein encoded by this gene plays a role in the immune system, suggesting a possible link with a cancer-promoting inflammatory or immunologicalresponse .
Co-author Dr Jane Figueiredo, from the University of Southern California, said: "Diet is a modifiable risk factor for colorectal (bowel) cancer.
"Our study is the first to understand whether some individuals are at higher or lower risk based on their genomic profile. This information can help us better understand the biology and maybe in the future lead to targeted prevention strategies."