N-nitroso compounds: assessing agreement between food frequency questionnaires and 7-day food records.

BACKGROUND: N-nitroso compounds are recognized as important dietary carcinogens. Accurate assessment of N-nitroso intake is fundamental to advancing research regarding its role with cancer. Previous studies have not used a quantitative database to estimate the intake of these compounds in a US population. OBJECTIVE: To address this gap, a database of N-nitroso values was developed in conjunction with an existing food frequency questionnaire (FFQ). In this article we report on the relative validity of the FFQ instrument modified to estimate intake of N-nitroso compounds. DESIGN: Intake estimates of 23 N-nitroso compounds from the FFQ were compared with those from 7-day food records in a cross-sectional study conducted from January 2005 through June 2006. SUBJECTS: A sample of 98 healthy adult subjects (aged 50.42+/-12.84 years) completed an FFQ and then recorded foods and beverages consumed on 7-day food records. RESULTS: Crude and energy-adjusted N-nitroso compounds intakes were significantly higher in the FFQ than the 7-day food records (P<0.001). Spearman correlations for crude and energy-adjusted N-nitroso intakes ranged from 0.004 to 0.48. By tertiles of N-nitiroso compounds, there was moderate agreement (kappa>0.30) for five compounds. Higher estimates of N-nitroso compounds by FFQ was explained by a greater proportion of subjects who reported eating foods high in N-nitroso compounds on FFQ than reported on 7-day food records. CONCLUSION: The modified FFQ with N-nitroso values is a useful tool for assessing N-nitroso intakes relative to a group, and captures all food items with N-nitroso compounds, including those foods with high concentrations and eaten sporadically.

Construction of an N-nitroso database for assessing dietary intake.

Dietary N-nitroso compounds are carcinogens synthesized during food processing from two main classes of precursors, oxides of nitrogen and amines or amides. Quantification of the dietary intake of N-nitroso compounds is significant to human cancers, including those of the stomach and upper gastro-intestinal tract, colon, and brain. Previous studies investigating these cancers primarily used proxy estimates of N-nitroso intake and not a full and complete database. In this report, we describe the development of a database to be used in conjunction with a food frequency questionnaire (FFQ) or twenty-four hour dietary records. Published analytical data for N-nitroso compounds were compiled and evaluated for inclusion in the database. The final database consisted of 23 different N-nitroso compounds for 500 foods from 39 different food subgroups. Next, database foods were matched to foods in a standard FFQ by imputation, or calculated value, or assumed zero. Using the FFQ modified with N-nitroso values, we evaluated the ability to compute N-nitroso intakes for a sample of healthy control subjects of cancer epidemiological studies. N-nitroso content of food items ranged from <0.01µg/100 g. to 142 µg/100 g and the richest sources were sausage, smoked meats, bacon, and luncheon meats. The database is useful to quantify N-nitroso intake for observational and epidemiological studies.