Intake of processed meat and its components is linked to increased risk for bladder cancer, according to the results of the large, prospective National Institutes of Health - AARP Diet and Health Study reported online August 2 in Cancer.

"Meat could be involved in bladder carcinogenesis via multiple potentially carcinogenic meat-related compounds related to cooking and processing, including nitrate, nitrite, heterocyclic amines (HCAs), and polycyclic aromatic hydrocarbons (PAHs)," write Leah M. Ferrucci, PhD, from the National Cancer Institute in Rockville, Maryland, and colleagues. "The authors comprehensively investigated the association between meat and meat components and bladder cancer."

Among 300,933 men and women who completed a validated food-frequency questionnaire, there were 854 cases of transitional cell bladder cancer identified during 7 years of follow-up. Using quantitative databases of measured values, the investigators estimated intake of nitrate and nitrite from processed meat and HCAs and PAHs from cooked meat, and they calculated total dietary nitrate and nitrite based on literature values.

For the fifth quintile vs the first quintile of red meat consumption, hazard ratio (HR) for bladder cancer was 1.22 (95% confidence interval [CI], 0.96 - 1.54; P for trend = .07). For the fifth vs first quintile of the HCA 2-amino-1 methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), HR was 1.19 (95% CI, 0.95 - 1.48; P for trend = .06). These HRs showed a borderline statistically significant increased risk for bladder cancer. There were also positive associations in the top quintile for total dietary nitrite (HR, 1.28; 95% CI, 1.02 - 1.61; P for trend = .06) and nitrate plus nitrite intake from processed meat (HR, 1.29; 95% CI, 1.00 - 1.67; P for trend = .11).

"These findings provided modest support for an increased risk of bladder cancer with total dietary nitrite and nitrate plus nitrite from processed meat," the study authors write. "Results also suggested a positive association between red meat and PhIP and bladder carcinogenesis."

Limitations of this study include lack of data on urination frequency and bladder infections and only limited data on beverage intake.

"Our findings highlight the importance of studying meat-related compounds to better understand the association between meat and cancer risk," senior author Amanda J. Cross, PhD, also from the National Cancer Institute, said in a news release. "Comprehensive epidemiologic data on meat-related exposures and bladder cancer are lacking; our findings should be followed up in other prospective studies."

The Intramural Research Program of the National Cancer Institute, National Institutes of Health, Department of Health and Human Services, supported this study in part.