The prospective study, published in the journal Cancer Epidemiology, Biomarkers & Prevention, also found no link to increased risk of the cancer for intake of either fresh or processed red meat, nitrosamines (compounds formed on digestion of nitrate and nitrite additives), or heme iron.
The researchers, led by Paula Jakszyn from the Catalan Institute of Oncology, Spain, explained that although previously published data from the European Prospective Investigation into Cancer and Nutrition (EPIC)study found no association between the intake of red meat and bladder cancer risk, “it does not preclude an association with certain aspects of meat intake, such as its content of heme iron, or nitrosamines.”
The analysis, which the authors claim is the first to look at important constituents of red meat such as heme iron and nitrosamines in relation to cancer risk, however did not find any evidence to support the idea that red meat or related compounds are associated with the risk of developing bladder cancer.
Red meat and cancer
Lots of attention – and headlines – have been dedicated to the health risks said to be associated with consumption of red meat.
High consumption has been associated with many poor health outcomes, including diabetes, cardiovascular disease and several types of cancer (including lung and colorectal, prostate, and bladder)
In 2007 the World Cancer Research Fund published a report that directly linked diet to cancer, reporting that red and processed meats posing particular risks.
The authors of the new analysis said that meat may be involved in bladder carcinogenesis via several biological mechanisms, including the formation of nitrosamines from heme iron – which is contained in fresh and processed meat.
They said that nitrosamines have been shown to cause a wide range of tumours, including cancer of the bladder, in over 40 animal species.
Recent studies have shown a positive association between dietary nitrite form processed meat and bladder cancer risk. But the intake of red meat – an important source of heme iron – has shown inconsistent findings with respect to bladder cancer in previous epidemiological studies.
The new study examined the association between red meat intake, dietary nitrosamines (N-Nitrosodimethylamine and endogenous nitrosocompounds), heme iron intake and bladder cancer incidence in the EPIC study.
The EPIC study involves more than a half million, people from 23 population centres in 10 European countries. During the study a lifestyle questionnaire was used to collect information about socio-demographic characteristics, lifestyle factors, dietary data, and medical history.
The authors reported that data on food consumption and complete follow-up for cancer occurrence were available for a total of 481,419 participants – with a mean follow-up of 8.7 years.
From the data proportional hazards models were used to estimate any possible association between meat intake, nitrosamines, heme iron, and bladder cancer risk.
Jakszyn and colleagues found no overall association between intake of red meat, nitrosamines or heme iron and bladder cancer risk.
They said that the lack of association did not vary with sex, high vs. low risk bladder cancers, smoking status, or occupational exposure (high vs. low risk) – whilst there were no differences observed when fresh and processed red meat were assessed separately.
“Our findings do not support an effect of red meat intake, nitrosamines … or heme iron intake on bladder cancer risk,” concluded the authors.
However, they added: “Considering the biological plausibility of an association between red meat intake and bladder cancer risk, further investigation is warranted given the limited available evidence.”
Source: Cancer Epidemiology, Biomarkers & Prevention
Published online ahead of print, doi: 10.1158/1055-9965.EPI-10-0971
“Red meat, dietary nitrosamines and heme iron and risk of bladder cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC)”
Authors: P.G Jakszyn, C.A. Gonzalez, L.L. Barroso, M.M. Ros, H.B. Bueno-de-Mesquita, N. Roswall, et al