Prospective study of meat intake and dietary nitrates, nitrites, and nitrosamines and risk of adult glioma.
BACKGROUND
The hypothesis that nitrosamine exposure may increase the risk of glioma has been circulating for several decades, but testing it has been difficult because of the ubiquitous nature of nitrosamine exposure. Diet has been the focus of many studies because it can substantially influence nitrosamine exposure, mostly from the endogenous formation of nitrosamines based on intake of nitrite and nitrate.


OBJECTIVE
The objective was to examine the relation between intakes of meats, nitrate, nitrite, and 2 nitrosamines [nitrosodimethylamine (NDMA) and nitrosopyrolidine (NPYR)] and glioma risk in a prospective analysis.


METHODS
Data from 3 US prospective cohort studies were combined for this analysis; 335 glioma cases were diagnosed during < or =24 y of follow-up. Dietary intake was assessed with food-frequency questionnaires. Nitrate, nitrite, and nitrosamine values were calculated based on published values of these nutrients in various foods over different periods in time. Cox proportional hazards models were used to estimate incidence rate ratios (RRs) and 95% CIs. Estimates from each cohort were pooled by using a random-effects model.


RESULTS
Risk of glioma was not elevated among individuals in the highest intake category of total processed meats (RR: 0.92; 95% CI: 0.48, 1.77), nitrate (RR: 1.02; 95% CI: 0.66, 1.58), nitrites (RR: 1.26; 95% CI: 0.89, 1.79), or NDMA (RR: 0.88; 95% CI: 0.57, 1.36) compared with the lowest category. No effect modification was observed by intake of vitamins C or E or other antioxidant measures.


CONCLUSIONS
We found no suggestion that intake of meat, nitrate, nitrite, or nitrosamines is related to the risk of glioma.
Michaud
Dominique S
DS
Department of Epidemiology and Public Health, Imperial College London, United Kingdom. d.michaud@imperial.ac.uk
Holick
Crystal N
CN
Batchelor
Tracy T
TT
Giovannucci
Edward
E
Hunter
David J
DJ
D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000453:epidemiology / Q000209:etiology*; D015331:Cohort Studies; D004032:Diet; D004034:Diet Surveys; D004128:Dimethylnitrosamine / Q000009:adverse effects*; D005260:Female; D005910:Glioma / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D008297:Male; D008460:Meat / Q000009:adverse effects*; D008461:Meat Products / Q000009:adverse effects; D008875:Middle Aged; D009566:Nitrates / Q000009:adverse effects*; D009573:Nitrites / Q000009:adverse effects*; D009602:Nitrosamines / Q000009:adverse effects*; D016016:Proportional Hazards Models; D012306:Risk
D009566:Nitrates; D009573:Nitrites; D009602:Nitrosamines; D004128:Dimethylnitrosamine