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

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N. Omidvar et al.
Since the 1970s, several attempts have been made
to design and validate dietary questionnaires (mostly
food-frequency questionnaires) as screening tools to
identify risk of poor vitamin A status. At least three
food-frequency questionnaires have been developed
and tested for preschool children in developing countries.
One of these originated in Indonesia [13] and
one in Mexico [14]. The third, developed by Helen
Keller International, is meant for local adaptation and
widespread use [15]. The Helen Keller instrument has
been evaluated in preschoolers in Thailand [7], Iran
[16], the Philippines, Guatemala, and Tanzania [6], and
in pregnant and lactating women in Bangladesh [17].
In the majority of these studies [6, 7, 14–16], serum
or plasma retinol has been used as the biomarker
for validation of the questionnaire; the Indonesian
study [13] used serum β-carotene. Only one study
[16], which was conducted on preschool children in
the province of Ilam, western Iran, failed to find a
significant correlation between serum retinol and
vitamin A intakes as estimated with the adapted Helen
Keller International instrument. In contrast to the findings
in populations at risk for vitamin A deficiency, in
vitamin A-sufficient populations there is generally no
relationship between intakes estimated from targeted
food-frequency questionnaires and serum retinol levels
[11, 18–20].
The present 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 in an area where overt hypovitaminosis A
is rare but mild deficiency is probably common.
Methods and materials
Study population and sampling
The study population included urban and rural
women from the Marand district of East Azarbaijan,
an agricultural area in northwest Iran. The study was
performed during the month of April (the beginning
of spring in the area), as part of an intervention study
focused on iron-deficiency anemia. For this study,
a convenience sample was selected from an ongoing
study of anemia in the region. The Research Council
of the Ministry of Health and Medical Education
approved the study protocol. Sampling was carried
out in two phases. In the first phase, a sample of 1,000
women was selected through random sampling from
those women under coverage of the primary healthcare
system in the area. Approximately 100 of these
women were diagnosed as anemic. In the second phase,
the latter group was matched with nonanemic women
based on parity, age, and area of residence. The sample
consisted of 187 healthy, nonpregnant, nonlactating
women 15 to 49 years of age.
Dietary assessment
Dietary intake was evaluated on two consecutive days
by a face-to-face interview using a 24-hour dietary
recall and a 43-item qualitative food-frequency questionnaire.
The interviewers were undergraduate nutrition
students who were given a two-day course in
dietary interviewing prior to the study and frequent
supervision by the first author (N. O.) during the
course of the study. A pictorial food album and
common household measures were used as memory
aids in the interview.
The 43-item food-frequency questionnaire (hereafter
referred to as the long food-frequency questionnaire)
was designed to evaluate the usual frequency
of consumption of 43 food items determined to be
major contributors to the Azerbaijani diet, as reported
by previous dietary studies in the area [4]. There was
special emphasis on foods that provide iron, vitamin C,
and vitamin A. For each item, the subjects were asked
to specify their frequency of intake over a day, week,
month, and year. “Never” and “rarely” were included
as possible options and were scored as zero.
Since the food-frequency questionnaire did not ask
for the portion sizes, the portion sizes were estimated
by using the portion sizes reported in the 24-hour
recalls and those reported in the national householdconsumption
survey that was available from neighboring
West Azerbaijan [Hooshiar-rad A, National
Institute of Nutrition and Food Technology, Tehran:
personal communication, 2000]. Vitamin A content
(retinol equivalents) for each typical portion was then
calculated based on the Iranian food-composition
table [21]. For food items whose vitamin A content
was not reported in the Iranian table, other tables
were used [22, 23]. In this way, a table of vitamin
A-containing local foods with usual portion sizes was
developed (appendix 1). Estimates of vitamin A intake
were obtained for each subject by multiplying the
frequency of consumption of each food item per week
by the vitamin A content of the medium-portion size
of that food and then summing over all intakes.
Biochemical assessment
A 3-cc sample of venous blood was obtained by
ante cubital puncture from nonfasting subjects at the
first visit. Specimens were immediately transferred to
shielded tubes, placed in a cool box, and taken to a
laboratory in Marand city. Serum was separated by
centrifugation within 2 hours and stored shielded
from light at –20 o C until analysis. Frozen serum sam-