Meat Preservatives Linked to Bladder Cancer?

New research suggests a link, but doctors debate the validity of the findings.

ByABC News
August 2, 2010, 8:28 AM

Aug. 2, 2010— -- High intake of ingredients known as nitrite and nitrate added to processed meats to aid preservation may be tied to bladder cancer -- but the relationship appears to be tentative, researchers say.

In a study that followed more than 300,000 men and women for seven years, dietary nitrite and nitrate, as well as nitrite alone, were associated with an increased risk of bladder cancer among individuals with the highest consumption of processed meat -- but the connection was of borderline statistical significance, according to Amanda J. Cross of the National Institutes of Health and colleagues.

In other words, the findings may have more to do with chance alone than with an actual causal link.

Consumption of processed meat itself was not associated with an increased risk of bladder cancer, Cross and colleagues reported in the journal Cancer.

"I think we should approach these modest results with caution," Dr. Shilajit Kundu, chief of urologic oncology at Northwestern Memorial Hospital, said in an interview with MedPage Today. Kundu was not involved in the study.

Nathan Bryan of the University of Texas, who also was not involved in the study, had similar concerns.

"There is not one single bit of data presented that is statistically significant by conventional statistical rules with 95 percent confidence," he said in an email to MedPage Today and ABC News. "With over 300,000 subjects, statistical significance should not be a problem if there is a clear and indisputable association."

Researchers suspect that meat could be involved in bladder cancer due to compounds related to cooking and processing, including nitrates, nitrites, heterocyclic amines (HCAs), and polycyclic aromatic hydrocarbons (PAHs).

Nitrate and nitrite are added to processed meat for preservation as well as enhancement of color and flavor. PAHs and HCAs can form during cooking.

These compounds and their metabolites are excreted through the urinary tract, which could lead to the development of cancer through contact with the cells lining the bladder or through systemic exposure, the researchers said.