Individuals who had the highest intake of nitrite in their diets had an almost 30% increased risk

A new epidemiological study has reported modest support for suggestions that some components in processed meat may increase risk of bladder cancer.

Consumption of red- and processed meat has previously been linked to an increased risk of developing certain types of cancer, and animal studies have indicated that certain compounds could be behind the purported link.

These compounds include nitrites and nitrates, which are added to processed meats as preservatives and to enhance colour and flavour and break down into N-nitroso compounds, as well as heterocyclic amine, polycyclic aromatic hydrocarbons.

For their new prospective study published online (ahead of print) in the Wiley Blackwell journal Cancer, Amanda Cross and colleagues from the US National Cancer Institute studied data amassed from dietary questionnaires completed by around 300,000 men and women aged 50-71 years in 1995 and 1996.

They were able to see what types of meat were consumed and how it was prepared, and from this calculate what people’s exposure to nitrates and nitrites would have been.

The participants were followed for 7 years for the NIH-AARP Diet and Health Study, during which time 854 people were diagnosed with bladder cancer.

Those with the highest intake of nitrite in their diets – from all sources including meat – and those with the highest intake of nitrate plus nitrite from meats, were seen to have a 28-29 per cent increased risk of developing bladder cancer compared to those with the lowest intakes.

Cross and colleagues concluded: “These findings provide modest support for an increased risk of bladder cancer with total dietary nitrite and nitrite plus nitrate from processed meat.”

In addition, a positive association was observed between red meat consumption and PhiP, the most abundant hetercyclic amine in cooked meat, and bladder carcinogensis.

“Our findings highlight the importance of studying meat-related compounds to better understand the association between meat and cancer risk,” said Cross. “Comprehensive epidemiologic data on meat-related exposures and bladder cancer are lacking; our findings should be followed up in other prospective studies.”

In particular a need has been observed for more studies focused on red meat and bladder cancer, and especially PhiP, “as prospective investigations of meat-related mutagens and this malignancy are lacking”.