Nutritional Epidemiology of Nitrogen Oxides: What Do the Numbers Mean?
Careful consideration of the study design, implementation, and accuracy of dietary assessment is necessary when evaluating epidemiologic data on nutrition. Prospective cohort studies on diet may avoid biases commonly observed in case–control studies and may be less problematic than large randomized experiments. Food-frequency questionnaires are a practical option for dietary assessment in large studies and provide useful information about intake of major nutrients. Biochemical measurements of nutrients are particularly important when a specific nutrient is poorly measured by other methods but it is essential to evaluate its sensitivity and the validity of this measure as an indicator of long-term intake. The great variability in nitrate and nitrite contents of foods and the short half-lives of their biochemical indicators complicate exposure measurement; however, some studies suggest that nitrate and nitrite intake in epidemiologic studies is feasible. The epidemiologic evidence for the relation between dietary nitrate and nitrite and cancer is limited and weak. There is no direct epidemiologic evidence relating nitrite and nitrate intake and cardiovascular disease, and this deserves investigation.
KeywordsNutrition Diet Epidemiology Food frequency questionnaire Cancer Cardiovascular disease
Coronary heart disease
Primary open-angle glaucoma
World Cancer Research Fund
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