The study was the work of researchers working on the European Prospective Investigation into Cancer and Nutrition-Oxford (EPIC-Oxford) and the findings were published in the online issue of the American Journal of Clinical Nutrition on 11 March.
In their background information, lead author Tim Key, a Cancer Research UK epidemiologist who is based at the University of Oxford, and colleagues wrote that few prospective studies (where groups of people are followed over a period of time) have looked at cancer rates among vegetarians, although the "5 a day" recommendation is geared to lowering risk of cancers and other diseases, so they decided to look at overall and individual cancer incidence rates among vegetarians and non-vegetarians.
For the study they examined EPIC data on 63,550 men and women aged 20 to 89 recruited throughout the UK during the 1990s. They got the cancer incidence figures from national cancer registries.
The results showed that:
- The standardized incidence ratio for all cancers for all participants was 72 per cent (that is lower than the overall population).
- Compared with meat eaters in the cohort, and after adjusting for age, sex and smoking status, the vegetarians in the cohort showed an 11 per cent lower incidence rate of all cancers.
- However, for colorectal cancer, vegetarians showed a 39 per cent higher incidence rate compared with meat eaters.
"The overall cancer incidence rates of both the vegetarians and the nonvegetarians in this study are low compared with national rates."
"Within the study, the incidence of all cancers combined was lower among vegetarians than among meat eaters, but the incidence of colorectal cancer was higher in vegetarians than in meat eaters," they added.
The researchers said their findings pointed to the need for more research in this area, especially given the rather surprising finding about higher colorectal cancer rates among the non meat eaters.
Red meat has been associated with higher rates of colorectal cancer.
Key told the press that the results were interesting and suggest there "might be some reduction in cancers in vegetarians and fish-eaters and we need to look carefully at that," according to a BBC report.
Key said there was a need to look more carefully at how meat fits in, because their findings didn't support the view that vegetarians ought to have lower rates of colorectal cancer.
He explained that it was very difficult to do studies on the links between diet and cancer.
It is possible that the people in this study were not necessarily representative of the population as a whole (as suggested by the first finding), for instance most of them were eating only moderate amounts of meat every day, and most of them were only just meeting the daily recommendation of 5 portions of fruit and vegetables a day, a leading nutritionist commented to the BBC.
"Cancer incidence in vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC- Oxford)."
Timothy J Key, Paul N Appleby, Elizabeth A Spencer, Ruth C Travis, Andrew W Roddam, and Naomi E Allen.
Am. J. Clinical Nutrition, first published online March 11, 2009.
Click here for Abstract.
Sources: Journal abstract, University of Chicago Medical Center, BBC.