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Relative validity of food frequency questionnaire nutrient estimates in the Black Women's Health Study
Shiriki K Kumanyika1, David Mauger, Diane C Mitchell
1Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, 8th Floor Blockley Hall, 23 Guardian Drive, Philadelphia 19104, USA. skumanyi@cceb.med.upenn.edu
Purpose:
The Black Women's Health Study (BWHS) was designed to investigate determinants of health and disease in US black women. More than 64,000 women are enrolled in the BWHS cohort. This study assessed the relative validity of the 68-item food frequency questionnaire (FFQ) used in the BWHS baseline questionnaire.
Methods:
Four hundred and eight BWHS enrollees were asked to provide three telephone, 24-hour recalls and one written 3-day food diary over a one-year period. Means and Pearson correlations were computed to compare estimates for energy, total fat, saturated fat, protein, carbohydrate, dietary fiber, calcium, iron, vitamin C, folate, beta-carotene, and vitamin E from the FFQ, recalls, and diaries.
Results:
Mean energy intake (kcal) was higher for the diary (1716) than the FFQ (1601) or recalls (1510). Other nutrient estimates (% kcal or per 1000 kcal) were similar across methods, except beta-carotene (FFQ higher). Correlations (energy-adjusted, except for energy, and corrected for intraperson variation) between the FFQ and the recalls were higher than for the diary data and were between 0.5 and 0.8, except for energy and vitamin E (both <0.3).
Conclusion:
The BWHS FFQ will support meaningful analyses of diet-health associations for 10 of the 11 energy-adjusted nutrient intake variables analyzed.