New findings provide evidence that people who eat a lot of red and processed meats have greater risk of developing bowel and lung cancer than people who eat small quantities. The research by Amanda Cross and colleagues at the US National Cancer Institute is published in the latest issue of PLoS Medicine.

The researchers used data from a large US diet and health study, which began in 1995 and involves nearly half a million men and women aged 50-71. Participants—none of whom had had cancer previously—completed a questionnaire about their dietary habits over the previous year. People whose red meat intake was in the top fifth of the range of intakes recorded in the study had an increased risk of developing colorectal, liver, lung and esophageal cancer when compared to people in the lowest fifth of consumption. People in the highest fifth of processed meat intake had an increased risk of developing colorectal and lung cancer. The incidences of other cancers were largely unaffected by meat intake.

These results provide evidence that people who eat a lot of red and processed meats have greater risk of developing colorectal and lung cancer than people who eat small quantities. They also indicate that a high red meat intake is associated with an increased risk of esophageal and liver cancer and that 1 in 10 colorectal and 1 in 10 lung cancers could be avoided if people reduced their red and processed meat intake to the lowest quintile.
 

The researchers allowed for factors such as smoking that might have affected cancer incidence, but it remains possible that other life-style factors may have had an influence. The study’s definitions of red meat and processed meat overlapped; bacon and ham, for example, were included in both categories. Thus, exactly which type of meat causes which type of cancer remains unclear. Most of the study participants were non-Hispanic white, so these findings may not apply to people with different genetic backgrounds. Nevertheless, they add to the evidence that suggests that decreased consumption of red and processed meats could reduce the incidence of several types of cancer.

In another article in the same issue of PLoS Medicine Anita Koushik and Jeanine Genkinger review the key research on the association between meat intake and cancer risk, including this new study.