While it was already known that eating processed meat increased a person's risk of developing bowel cancer, the study, published in the journal PLOS Genetics on Friday, found that for people who carry a common genetic variant, eating processed meat carries an even higher risk than for those who do not carry the gene.

Bowel cancer is the second most common cancer in both men and women in Australia. One in 10 Australian men and one in 15 Australian women will be diagnosed with bowel cancer by the time they reach 85. Almost 4000 Australians died of bowel cancer in 2011.

One of the researchers, Li Hsu, of the Fred Hutchinson Cancer Centre in Seattle, said the discovery provided "an important new insight into disease development".

Another of the researchers, Jane Figueiredo from the University of Southern California, said the discovery could lead to more targeted cancer prevention strategies.

"Diet is a modifiable risk factor for colourectal cancer," Dr Figueiredo said. "Our study is the first to understand whether some individuals are at higher or lower risk based on their genomic profile."

About 30 genetic variants that make a person more susceptible to bowel cancer have been pinpointed throughout the genome. The study, which involved more than 18,000 patients from Australia, the US, Canada and Europe, is the first large-scale, genome-wide analysis of genetic variants and dietary patterns. Researchers searched 2.7 million genetic variants to identify those linked with the consumption of meat, fibre and fruit and vegetables.

Exactly how specific foods affect the activities of genes has not been established.

The researchers said a "plausible though speculative" explanation for its findings was that processed meat triggered an inflammatory or immunological response.