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Department of International Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322;
*
Program in International Nutrition, Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853–6301; and
Rural Unit for Health and Social Affairs Department, Christian Medical College and Hospital, Vellore 632004, India
3To whom correspondence and reprint requests should be addressed.
 |
ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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KEY WORDS: • preschool children • vitamin A • dietary intakes
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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,
Shankar et al. 1996
, Zeitlin et al. 1992
), but few have examined the relative contributions of the
different sources of vitamin A that vary in bioavailability. Another potentially inexpensive and often ignored source of preformed retinol
is breast milk. Studies from Bangladesh, Indonesia and Malawi have shown that children who are breast-fed longer have a significantly
lower risk for the xerophthalmia and nutritional blindness that result from severe vitamin A deficiency (Mahalabanis 1991
,
Tarwotjo et al. 1982
, West et al. 1986
).
Despite current recommendations that promote sustained breast-feeding into y 2 of life (UNICEF 1993
),
little is known regarding the contribution of breast milk to total
vitamin A intakes in this age group (Institute of Medicine 1991
).
Promoting dietary change to improve vitamin A intakes has been recommended as a feasible long-term strategy in combating vitamin A
deficiency among young children (WHO 1994
). However, rigorous evaluation of such interventions depend on the
ability to collect good quality dietary data. The assessment of vitamin A intakes is problematic because they are highly variable and are
affected greatly by factors such as season and the consumption of specific foods such as liver which are extremely rich sources of
retinol (Willett 1998
). In many developing countries in
which food processing and storage are limited, fruits such as papaya
and mangoes are available for only 2–3 mo in a year. A wide variety of dietary assessment methodologies that range from the qualitative
(food-frequency methods) to detailed quantitative methods (24-h food recall; 3- or 7-d food records) are available to assess dietary intakes
of vitamin A at the household and community level. More recently, the (semi) quantitative food-frequency questionnaire is being
recommended as a useful and simple tool to assess dietary intake of vitamin A in different populations. The International Vitamin A
Consultative Group (IVACG)4
developed such an instrument for use in developing countries; it is
comprised of a qualitative food-frequency questionnaire combined with semiquantitative estimates of actual consumption using a modified
24-h recall (IVACG 1989
). The Helen Keller International
(HKI) Food Frequency Questionnaire, a qualitative 7-d recall of the number of times that a child consumed selected vitamin A rich foods, is
simpler and easier to use, but appears to be useful to identify communities and not individuals at risk of vitamin A deficiency
(HKI 1992
, Sloan and Rosen 1997
). At the
time that these methodologies were being developed and tested, the senior author of this paper developed and applied a quantitative
food-frequency questionnaire, adapted to local conditions and considering seasonality, to collect dietary data on a large sample of
young children, as part of a larger vitamin A intervention study that
was conducted in rural South India (Ramakrishnan 1993
).
The main objectives of this paper are as follows: 1) to assess and describe the adequacy of dietary intakes of vitamin A
(ß-carotene, preformed retinol and total intake) among South Indian children (12–47 mo) using a modified quantitative food-frequency
questionnaire in a developing country setting and 2) to identify the determinants of vitamin A intakes from different dietary
sources.
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SUBJECTS AND METHODS |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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This analysis used dietary data from a randomized
placebo-controlled vitamin A intervention trial that was conducted
during 1989–1991 in 12 villages in South India. Health and nutrition
education messages were delivered to mothers by village health workers
in all 12 villages; growth monitoring took place in 6 villages. Details
of the trial and study population are described elsewhere
(Ramakrishnan 1993
). The original study was approved by
the Human Subjects Committee at Cornell University, and informed consent was obtained from the parent or guardian of all participating
children.
Data collection.
A quantitative food-frequency questionnaire appropriate to the
local conditions was developed and pretested by the first author, a
native of the region, based on market surveys and interviews with key
informants, including field workers and mothers. The instrument was
administered once to mothers of all children between 12 and 47 mo of
age (n = 683) between January and April 1991 at the
end of the vitamin A intervention trial. In most cases, there was only
one child per household, but 11% of the 615 households contributed >1
child. Trained female field workers interviewed mothers about the
habitual frequency of consumption of common sources of vitamin A by
their preschool child. The vitamin A–rich foods included were locally
available dark green leafy vegetables (e.g., amaranth or drumstick
leaves), yellow and orange fruits and vegetables (e.g., mangoes,
papayas, yellow pumpkin or carrots), eggs, milk and meat products. For
seasonal foods (e.g., mangoes or yellow pumpkin), mothers were asked to
state the number of months in the year during which these foods were
available; the frequency of consumption referred only to the period in
which they were available. Mothers were also asked to indicate the
usual portion size that their child consumed. Commonly used household
utensils such as ladles and cups were used to facilitate recall of
portion sizes. The volumes and weights of local utensils were estimated
and converted by the trained workers using standard plastic measuring
cups and spoons. Details of locally used recipes were also obtained.
Mothers who were still breast-feeding were asked to report the
number of times they breast-fed their child in the previous 24 h. Although the instrument was not formally validated by collecting
data over different periods of time and by comparison with other
biological indicators of vitamin A deficiency, it is similar to the
IVACG method, which has been validated (Abdallah and Ahmed 1993
, Nimsakul et al. 1994
).
Sociodemographic information collected included household size and
composition, maternal education (number of years of schooling),
father's occupation, ownership of land, livestock and other household
possessions such as radio, bicycle and television. Details on infant
feeding practices such as duration of breast-feeding, timing of
introduction of complementary foods and type of complementary foods
were also collected using pretested questionnaires. Length or height
(in the case of children over 24 mo) and weight were collected for all
children using standard measurement techniques (Lohman et al. 1988
). Details of all births that had been monitored
prospectively since 1987 were used to determine the ages of all
children. All data were collected by trained field workers as part of
the original study, entered in the field using DBASEIII and
subsequently analyzed using SAS (SAS 1996
).
Data analysis.
Anthropometric data were expressed as Z-scores using the WHO/U.S. National Center for Health Statistics (NCHS) reference values. Stunting and wasting were defined as Z-scores below -2 of the NCHS mean for height/age and weight/height, respectively.
The various responses for the frequency of intake of vitamin A–rich
foods were combined into the following categories: 1–3 times per week,
1–3 times per month (including responses such as monthly and
bimonthly) and rarely (including frequencies from less than once a
month to never). Estimated vitamin A intake from nonbreast milk sources
was calculated from the reported frequency of intake, number of months
in a year that the food was available, mean serving size and vitamin A
content (total, preformed retinol and ß-carotene) of the foods by
using the values published by the Indian National Institute of Nutrition (NIN) (1985)
. Intakes for seasonal foods were
prorated to reflect the number of months they were available. The daily
vitamin A intake for a given food source was calculated as follows:
daily vitamin A intake [retinol equivalents (RE)] = [(number of
times/y) · (vitamin A content of serving)]/365 where number of
times/y = (number of times/mo) · (number of mo
available/y), and vitamin A content of an average serving
= weight per serving (g) · vitamin A content of the food (RE/g)
The vitamin A intakes from the various food sources were then summed
and expressed as average daily intake. These calculations was also done
separately for ß-carotene and retinol intakes. Because the
distributions of intakes were highly skewed, log-transformed values
were used in the analysis. The amount of breast milk vitamin A was
based on published estimates of average breast milk intake and vitamin
A content of breast milk from recent reviews (Newman 1993
, WHO 1998
). The estimates of 549 and 320 mL
were used for volume of breast milk intake during y 2 and 3 of life,
and 309 RE/L and 130 RE/L were used for vitamin A content,
respectively. On the basis of the above values, the contribution of
breast milk was estimated as 170 and 39 RE/d for breast-fed
children during y 2 and 3 of life.
Multivariate analyses were done using the General Linear Models
approach (SAS-GLM), in which the dependent variables were the
log-transformed values of preformed retinol, ß-carotene and total
vitamin A intakes from nonbreast milk sources. The independent
variables included age (in months), nutritional status using weight/age
Z-score, sex of the child (male/female), whether the child was from
a growth monitoring village (Yes/No), current breast-feeding status
(Yes/No), maternal education and father's occupation. Although data
were available for other indicators of socioeconomic status (SES),
father's occupation was found to be the best indicator of SES on the
basis of previous correlation analysis (Ramakrishnan 1993
) and was used in the final models. The main occupational
groups included coolie laborers,
beedi-rollers, semiskilled tradesmen, landed farmers and
government employees. Both the beedi-rollers and coolies generally
worked for daily wages and owned little or no land. They comprised the
lowest socioeconomic groups. Government employees and landed farmers
had higher incomes and owned more land, livestock and household
possessions.
|
RESULTS |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. The prevalence of stunting and wasting among the children was 40.4 and
15.1%, respectively. Agriculture was the mainstay of this population;
almost half of the population were landless and worked as coolie
laborers for payment in cash and/or kind on others' land and belonged
to the socially most deprived castes. Although nearly 70% of the
fathers had some education, only 5% of mothers had completed high
school and more than half of them had no formal education. The median
household size was 5 (range 3–24) and nearly half of the households
were either joint or extended families.
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and
3, respectively. Although the majority of the children were reported to
consume green leafy vegetables such as amaranth and drumstick leaves at
least weekly, yellow orange vegetables and fruits such as papaya, mango
and pumpkin were consumed less frequently and were available for only
part of the year. For example, mangoes were available for only 2–3 mo
during the summer. The reported availability of yellow pumpkin and
papayas, however, was more variable and ranged from 3 to 8 mo in a
year. Animal products such as milk, meat and eggs were consumed less
frequently. Less than one third of the children consumed these foods at
least once a week, whereas a large proportion rarely or never consumed
them. The only exception were children in some villages who regularly
attended the government-sponsored preschool creches (balwadis) and
received one boiled egg either weekly or every 2 wk. The type of meat
consumed was strongly dictated by caste and was commonly beef or goat
meat. Specifically, lower caste was associated with increased meat
consumption, especially beef, which is taboo for caste Hindus. Poultry
and pork, which are more expensive, were consumed less frequently.
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). Most of this, however, came from plants (ß-carotene). The median
contribution of preformed retinol (mainly from animal foods) was only
9.3%. Among the various foods, carrots and eggs were significantly and
highly correlated (P < 0.01) with total intakes of
vitamin A from nonbreast milk sources. Total vitamin A intake from
nonbreast milk sources, i.e., home diet, increased significantly with
age until about 2 y of age, beyond which it remained constant
(Table 4)
. Similar patterns were seen for ß-carotene intakes.
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); these differences remained significant (P < 0.05)
even after controlling for the effects of potential confounders, except
for ß-carotene (Table 5
). Vitamin A intakes were the lowest for children whose mothers had no
education and the highest for those who had completed high school (Fig. 1
B). Higher SES (Fig. 1
C), was also positively
associated with greater intakes of ß-carotene, retinol and total
vitamin A (P < 0.05). The children of
beedi-rollers and coolies had the lowest intakes. The effects of
maternal education and SES remained significant for total intakes and
retinol but not for ß-carotene, after controlling for confounding
factors (Table 5)
. Age was not significantly associated with retinol
intakes when current breast-feeding status was controlled for.
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Vitamin A intake from nonbreast milk sources was significantly lower
for children who were currently breast-fed compared with those who
were not, especially during y 2 of life (Fig. 2
). These differences were significant even after controlling for other
confounding variables (Table 5)
. However, vitamin A intake from
nonbreast milk sources increased with age among those who were
currently breast-fed, whereas that was not the case for those who
were not breast-fed. Because the prevalence and frequency of
breast-feeding declined with increasing age, we can assume that the
volume of breast milk consumed and therefore the contribution of breast
milk to total vitamin A intakes most likely declined with age. Using
published estimates of breast milk volume and composition, half of the
currently breast-fed children met >90% the Indian recommended
dietary allowance (RDA) of 250 RE (NIN 1985
) during y 2
of life, but this declined to ~60% of this RDA in y 3 of life.
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|
DISCUSSION |
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TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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used monthly 24-h recalls and found that animal products such as beef,
goat, chicken or eggs were rarely consumed (<2%) by preschool-age
children in Bangladesh. Although mothers reported that green leafy
vegetables were consumed frequently by their children in our study, the
actual amounts consumed were extremely small. On the other hand,
children tended to consume larger servings of fruits such as papayas
and mangoes, which were available for only a few months in the year.
This pattern of intake, combined with low fat intakes and worm
infestation, and the recent debate on the reduced bioavailability of
vitamin A from green leafy vegetables (De Pee and West 1996
), raises important questions on the ability of these diets
to meet vitamin A requirements of young children without the inclusion
of animal products and consideration of the role of breast milk.
The findings of this study support the importance of breast milk as a
major source of preformed retinol in the diets of young children.
Although we are limited by the lack of data on the volume and
composition of breast milk, our results suggest that breast milk does
make a significant contribution to the total vitamin A intake of
children during y 2 of life. Using the Indian RDA of 250 RE of vitamin
A for children aged 1–3 y (NIN 1985
), our estimates
show that children who were not being breast-fed met only 60% of
this RDA. The contribution of nonbreast milk sources was even lower
(10–40%) among those who were being breast-fed. It should be
noted that these estimates would be even lower if the RDA of 400 RE
from developed countries was used (NRC 1990
).
Zeitlin et al. (1992)
concluded that average intakes of
preschool age children in Bangladesh were close to or even > 100% of the Indian RDA of 250 RE when the contribution of breast milk
was taken into account. More recently, Persson et al. (1998)
reported the contribution of breast milk as 164.4 RE/d
and 93.6 RE/d during y 2 and 3 of life; this represents 41 and 23% of
the recommended safe daily intake of 400 RE for vitamin A,
respectively. Although the estimates for the younger children are
similar to those reported by Newman (1993)
, they are
threefold higher for the older children, possibly because it was
assumed that breast milk retinol concentrations remained the same. This
may not in fact be true because maternal stores become depleted over
time in these settings.
An interesting finding of this study that merits special attention is
the significant gender-based difference in dietary intakes of
vitamin A. Girls were at increased risk for lower intakes of vitamin A,
especially preformed retinol even after adjusting for the effects of
age, SES, maternal education and current breast-feeding status.
Although few studies have demonstrated such differences, these findings
are not entirely surprising in light of the evidence of
gender-based discrimination against girls in other practices such
as female infanticide or reduced access to health care in South Asia
(Chen et al. 1981
, World Bank, 1994
). In
contrast, Backstrand et al. (1997)
did not find evidence
of gender-based differences in dietary quality and intakes of
several micronutrients among preschoolers in Mexico.
Both SES and maternal education were important determinants of vitamin
A intakes. Studies from other parts of the world, namely, Mexico and
Kenya, using different dietary methods, have also shown that the
consumption of micronutrient-rich foods, especially animal foods,
was strongly correlated with measures of household wealth
(Kennedy and Oniang'o 1993
, Zeitlin et al. 1992
). However, in this study, when breast-feeding status
was controlled for, SES based on father's occupation was no longer
associated with vitamin A intake from plants; this may be explained by
the fact that children who were currently breast-fed tended to be
of lower SES (P = 0.059) compared with those who were
not. Nevertheless, total vitamin A intake from nonbreast milk sources
increased significantly with improved SES and maternal education
independently of breast-feeding status and was consistently lower
for those who were currently breast-fed compared with those who
were not, at all levels of SES and maternal education. Children of
higher SES, who were not breast-fed, were more likely to meet their
requirements (mean intakes were 212 RE/d) compared with those in the
lower SES groups. Zeitlin et al. (1992)
also found in
Bangladesh that vitamin A intake from vegetables was not associated
with indicators of SES, but that vitamin A intake from animal sources,
which was negligible, was positively associated with maternal education
and wealth.
Some of the limitations of these findings are methodological issues
related to the estimates of intake. Recall bias may have affected the
estimates because mothers were asked to use the past year as the period
of recall. This may be more problematic especially for younger children
whose diets are constantly changing, and it is likely that mothers were
reporting habitual intakes for a more recent period of time, i.e., the
past 2–3 mo. Another concern is that differences in the analytical
methods, assumptions of bioconversion and the manner in which the food
samples were collected may cause systematic errors in the absolute
intakes (Booth et al. 1992
). However, these
problems are not unique to the Indian database, but are common to use
of food composition tables and are less likely to affect the
conclusions regarding the patterns of intake.
In conclusion, although food-based approaches are clearly the
desirable strategy in eliminating vitamin A deficiency in a sustainable
manner, these findings show that a careful understanding of the
patterns of intake and their determinants is necessary in planning and
implementing the appropriate programs that will be most beneficial and
cost effective. Promoting the consumption of animal products may be a
viable means of improving dietary quality and child health because the
intake of not only vitamin A but also of several other micronutrients
such as iron, zinc, and vitamin B-12 could be simultaneously improved
(Allen et al. 1992
, Demaeyer 1989
).
However, this may not be a feasible alternative in some cultures
because of socioeconomic, religious and cultural constraints. It is in
this context that the importance of breast milk as an inexpensive
source of retinol, especially for the poor, cannot be ignored. We must
pursue strategies such as the provision of vitamin A supplements to
lactating women soon after delivery, which has been shown to improve
the retinol content of breast milk (Stoltzfus et al. 1993
), and perhaps multivitamin mineral supplements during
pregnancy (Ramakrishnan et al. 1999
).
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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2 Supported in part by awards from UNICEF and the Ford Foundation.
4 Abbreviations used: HKI, Helen Keller International; IVACG, International Vitamin A Consultive Group; NCHS,
National Center for Health Statistics; NIN; National Institute of Nutrition (India); RDA, recommended dietary allowance; RE, retinol
equivalents; SES, socioeconomic status.
Manuscript received January 26, 1999. Initial review completed April 24, 1999. Revision accepted July 19, 1999.
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