Design and validation of a food frequency questionnaire to assess the dietary intake for adults in pastoral settings in Northern Tanzania.

Objective: Food frequency questionnaires are widely used as a dietary assessment tool in nutritional epidemiology to determine the relationship between diet and diseases. In Tanzania, there are several cultural variations in food intake which makes it necessary to design and validate a culture-specific food frequency questionnaire (CFFQ). Therefore, we designed a 27-items CFFQ and examine its validity in pastoral communities. Validity of CFFQ was assessed by comparing nutrient intake estimated from the CFFQ against the average from two 24-h diet recall (2R24). Spearman's correlation coefficients, cross classification and Bland-Altman's methods were used to assess the validity of CFFQ.

Results: A total of 130 adults aged 18 years and above completed both CFFQ and 2R24. Correlation coefficients between CFFQ and 2R24 ranged from low (r = - 0.07) to moderate (r = 0.37). The correlation coefficients were moderately significant for kilocalories (r = 0.31, p < 0.001), carbohydrate (r = 0.33, p < 0.001), magnesium (r = 0.37, p < 0.001), and iron (r = 0.34, p < 0.001). On average, about 69% of participants were correctly classified into the same or adjacent quartile of energy and nutrient intake, while 9% were misclassified by the CFFQ. Bland-Altman's plot demonstrated that the CFFQ had acceptable agreement with the 2R24.