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.