F&N Bulletin Vol 23 No 1b - United Nations University

Development and validation of a short food-frequency
questionnaire for screening women of childbearing age
for vitamin A status in northwestern Iran
Nasrin Omidvar, Mahmood Ghazi-Tabatabie, Gail G. Harrison, Shahriar Eghtesadi,
Soltan-Ali Mahboob, and Mahdi Pourbakht
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 foodfrequency
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 µg/dl for three
subjects, while an additional 34 subjects (18%) had
values between 21 and 30 µg/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
Nasrin Omidvar, Shahriar Eghtesadi, Soltan-Ali Mahboob,
and Mahdi Pourbakht are affiliated with the School of
Nutrition and Public Health, Tabriz University, in Tabriz,
Iran. Mahmood Ghazi-Tabatabie is affiliated with the School
of Social Sciences, Tabriz University. Gail G. Harrison is
affiliated with the University of California, School of Public
Health and Center for Human Nutrition in Los Angeles,
California, USA.
questionnaire is relatively valid and potentially useful
in identifying women at risk for vitamin A deficiency
in this population.
Introduction
Vitamin A deficiency is a major public health problem
in less-developed and developing countries and has
a high impact on morbidity and mortality [1, 2].
About 100 million children in the world are estimated
to be vitamin A deficient [3]. A high percentage of
women of childbearing age suffer from subclinical
vitamin A deficiency: 10% to 20% of pregnant women
worldwide are vitamin A deficient [3]. Iran, like most
of the Middle East, is not an area of severe vitamin A
deficiency, but mild-to-moderate vitamin A deficiency
is widespread in vulnerable groups. Dietary studies
in Iran conducted from the 1960s through as recently
as 1995 indicate an inadequate intake of vitamin A,
especially in rural areas [4].
A variety of biochemical methods exist to evaluate
the vitamin A status of communities [5]; however, biochemical
methods are invasive and relatively expensive
[6, 7]. Thus, development of alternative methods
that are inexpensive and easy to perform in the field
setting is a priority. In this context, dietary assessment
methods have been recommended for identifying
groups at risk for vitamin A deficiency and for assessing
food habits as a basis for designing effective interventions
to improve vitamin A status [8]. The targeted
food-frequency questionnaire has been proposed as a
simple, inexpensive dietary assessment method with
low interview and recording error as well as minimal
recall bias [9]. However, food-frequency questionnaires
need to be tailored to the food-consumption patterns
and culture of the population under study [10, 11].
Biochemical indicators can then be used to validate
the food-frequency questionnaire, identify food items
with maximum discriminating effect, and exclude
those with little predictive value, despite having high
content of the nutrient of interest [12].
Food and Nutrition Bulletin, vol. 23, no. 1 © 2002, The United Nations University. 73