Validating a semi-quantitative food frequency questionnaire to assess regional diet in a study of cancer in South West Nigeria

Purpose: Cancer burden is rising rapidly in Nigeria, the most populous country in sub-Saharan Africa; this trend may in part be attributable to diet. We developed and validated a semi-quantitative food frequency questionnaire (FFQ) to assess regional diet in Nigeria. Methods: We recruited 68 adult participants from rural and urban settings in South West Nigeria. We developed an FFQ administered at baseline and assessed its validity using 3 dietary recalls (baseline, 7 days post baseline, 3 months post baseline). We calculated Spearman’s rank correlation coefficients and energy-adjusted de-attenuated correlation coefficients for food items and macronutrients. We evaluated cross-classification using quartiles of macronutrient intake. Results: Energy-adjusted de-attenuated food item correlations between the FFQ and dietary recalls ranged from -0.08 (smoked beef/goat) to 0.73 (fried snacks) for the average intake from the first 2 recalls (2DR) and from -0.05 (smoked beef/goat) to 0.75 (smoked fish) for the average of all 3 recalls (3DR). Macronutrient correlations ranged from 0.15 (fat) to 0.37 (fiber) for the 2DR and from 0.08 (fat) to 0.41 (carbohydrates) for the 3DR. The percent of participants classified in the same quartile ranged from 16.4% (fat) to 32.8% (fiber, protein) for the 2DR and from 25.6% (fat) to 34.9% (carbohydrates) for the 3DR. Agreement improved when including adjacent quartiles, from 65.5% (carbohydrates) to 70.5% (fat, fiber) for the 2DR and from 62.8% (protein) to 76.8% (carbohydrate) for the 3DR. Conclusion: Our semi-quantitative FFQ was reasonably valid for ranking intake of certain foods and macronutrients in adults in South West Nigeria.