Development and validation of a short food-frequency questionnaire for screening women of childbearing age for vitamin A status in northwestern Iran.

Abstract

A high percentage of women in their childbearing years suffer from subclinical vitamin A deficiency; 10% to 20% of pregnant women worldwide are vitamin A deficient. This study aimed to design and validate a short food-frequency questionnaire to serve as a simple screening tool for vitamin A status in women of childbearing age. The sample consisted of 187 healthy, nonpregnant, nonlactating women 15 to 49 years of age, from urban and rural areas of Marand district in East Azerbaijan. Dietary intake was evaluated by a face-to-face interview using a 24-hour dietary recall for two consecutive days and a 41-item qualitative food frequency questionnaire. Height, weight, and serum retinol were measured. Serum retinol values were less than 20 micrograms/dl for three subjects, while an additional 34 subjects (18%) had values between 21 and 30 micrograms/dl. Principal-component analysis performed on the food-frequency questionnaire identified five components that together defined 34.4% of the variance in estimated vitamin A intake and were used to derive a 20-item short food-frequency questionnaire. Internal consistency of the short instrument was acceptable (Cronbach's alpha = .59). Serum retinol was significantly correlated with total vitamin A intake and with intake of vitamin A from plant sources, as estimated by the short food-frequency questionnaire. Important sources of provitamin A in these women's diets included some not typical of other populations: nuts and green leaves of types used elsewhere in small quantities as herbs, but important in Iran because the amount and frequency of consumption are relatively high. We conclude that the questionnaire is relatively valid and potentially useful in identifying women at risk for vitamin A deficiency in this population.