| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Original Research Communications |
1 From the Nutrition Center of the Philippines, Manila; the Center for Human Nutrition, the Department of International Health, the School of Hygiene and Public Health, Johns Hopkins University, Baltimore; Helen Keller International, New York; and Craft Technologies Inc, Wilson, NC.
2 Supported by a cooperative agreement (no. 5018-251/5019-251) between The Center for Human Nutrition, Johns Hopkins University, The Nutrition Center of the Philippines, and Helen Keller International,and by a cooperative agreement (no. HRN-A-00-97-0015) between Johns Hopkins University and the Office of Health and Nutrition, US Agency for International Development. 3 Address reprint requests to RDW Klemm, Center for Human Nutrition, Department of International Health, School of Hygiene and Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, MD 21205. E-mail: rklemm{at}jhsph.edu.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Objective: This study assessed the efficacy of consumption of a vitamin A–fortified wheat-flour bun (pandesal) on the vitamin A status of school-age children.
Design: This was a double-masked clinical trial conducted in 396 and 439 children aged 6–13 y attending 4 rural schools in the Philippines. The children were randomly assigned to a vitamin A–fortified (experimental) or nonfortified (control) group. A 60-g vitamin A–fortified pandesal (containing 
133 µg retinol equivalents) or a nonfortified pandesal was consumed by the children 5 d/wk for 30 wk. Vitamin A status, hemoglobin concentration, anthropometric status, morbidity, and dietary intake were assessed at baseline and 30 wk later. A modified relative dose response (MRDR) was assessed in a subsample of 20% of the children (75/group) with the lowest initial serum retinol concentration at the 30-wk follow-up.
Results: Baseline serum retinol significantly modified the effect of the intervention. The fortified group, whose initial serum retinol concentrations were below the median, had a 0.07 ± 0.03-µmol/L greater improvement in serum retinol at the 30-wk follow-up than did the control group (P = 0.02). Improved vitamin A status was also evident in the MRDR subsample. End-of-study differences in the MRDR showed that vitamin A– fortified pandesal intake decreased the percentage of children with inadequate liver vitamin A stores by 50% (15.3% compared with 28.6%; P = 0.05).
Conclusions: Daily consumption of vitamin A–fortified pandesal significantly improved the vitamin A status of Filipino school-age children with marginal-to-low initial serum retinol concentrations.
Key Words: Vitamin A fortification • wheat flour • vitamin A deficiency • modified relative dose response • schoolchildren • Philippines
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
An appropriate food vehicle would be one that is widely and regularly consumed by the target population within a relatively narrow range of intakes and that would not change appreciably in appearance, color, texture, or organoleptic properties with the addition of vitamin A (4–6). Furthermore, the potency of the added vitamin A needs to remain high under usual conditions of processing, transport, storage, and cooking. In addition, it is important that the cost of adding vitamin A to the food carrier does not increase the cost of the product to the point where the target group cannot afford to consume it regularly.
Fortification of foods such as margarine, milk, and bread with vitamin A has long been a practice in Western countries (7). Foods that have been fortified with vitamin A for use in developing countries include sugar (8), wheat (9), rice and other grain products, tea, dairy foods, margarine, edible oils, formula foods, and specialty items. However, vitamin A–fortified monosodium glutamate (in Southeast Asia) (10) and sugar (in Central America) (7, 11) are a few of the products that have undergone extensive testing, are distributed widely in-country, and have been evaluated for their public health effects. Surprisingly, the effectiveness of vitamin A–fortified staple grain products has yet to be tested.
With the consumption of wheat rising in many developing countries (12), fortification of wheat flour with vitamin A may provide an opportunity to improve vitamin A intake and status. The technology exists for fortifying wheat flour with dry vitamin A, the retention of which exceeds 95% for up to 1 y at temperatures of 
40°C (4). About 70% of vitamin A activity remains after baking traditional bread products with fortified flour (1), suggesting that fortified wheat could provide an effective dietary means of improving vitamin A status.
The present study evaluated the efficacy of daily consumption of a vitamin A–fortified wheat-flour bun (known in the Philippines as pandesal) in improving the vitamin A status of school-age Filipino children, as assessed on the basis of serum retinol concentrations and the results of the modified-relative-dose-response (MRDR) test—which indicates the status of vitamin A reserves in the liver.
|
SUBJECTS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
60 km south of Manila. This area was chosen because, in 1994, data from children in nearby schools showed a mean (±SD) serum retinol concentration of 0.92 ± 0.46 µmol/L, with a large proportion of children exhibiting low serum retinol concentrations (FS Solon, personal communication, 1997). School-age children were selected because this population (aged 6–13 y) is not routinely supplemented with high-potency vitamin A in the Philippines. The purpose and procedures of the study were explained to the parents or caretakers of children in grades 1–6. Almost all of the parents allowed their children to participate and signed an informed consent form. The trial was reviewed and approved by the Committee on Human Research at Johns Hopkins School of Public Health, Baltimore; the National Nutrition Council, Department of Agriculture, Manila, Philippines; and the Council for Health Research and Development, Department of Science and Technology, Manila, Philippines.
Sample size
Sample size requirements were calculated by using a difference of 0.084 ± 0.42 µmol/L between the intervention and control groups, which was found previously in a vitamin A–fortification trial (13). To detect this magnitude of difference in serum retinol concentrations between the 2 groups, with a power of 0.80 and an 
of 0.05, 2 groups of 393, or a total of 786, individuals were required. To account for potential dropouts, all children (n = 922) in grades 1–6 from the 4 schools were invited to participate in the baseline data-collection phase. We obtained consent and baseline serum samples from 918 of these children; however, we obtained a 6-mo serum sample from only 835 of these children.
Treatment groups
At each school, the children were individually randomly assigned to either the vitamin A–fortified (experimental; n = 396) or nonfortified (control; n = 439) group. Each child received one 60-g pandesal, 5 d/wk, for 30 wk as part of a school-feeding program. A 60-g pandesal typically contains 831.6 kJ, 6.1 g protein, 2.5 g fat, 37.7 g carbohydrate, 14.4 mg Ca, 45 mg P, 1.8 mg Fe and niacin, and <0.2 mg thiamine and riboflavin (14). The fortified group received pandesal made from vitamin A–fortified wheat flour (see below); the nonfortified group received the standard product.
Data collection
Baseline assessment of participating children included phlebotomy to obtain 5 mL blood (2 mL serum) for immediate hemoglobin (HemoCue system; Hemocue, Angelholm, Sweden) and later serum retinol determination, a single 24-h dietary recall, an ocular examination for signs of xerophthalmia, anthropometric assessment (weight and height), and a 7-d morbidity recall of fever and diarrhea.
In a 10% subsample of the children, 3-d 24-h dietary recalls were performed at baseline and at the 30-wk follow-up, in addition to a 1-d dietary recall midway through the study. The protocol called for children with xerophthalmia to be treated with high-potency vitamin A, referred for additional treatment and follow-up, and excluded from the trial; however, no children were found to have xerophthalmia. Ill children were referred to the local government health clinic for treatment but remained in the study. At the 6-mo follow-up, baseline assessment procedures were repeated.
Weight and height measurements were converted to weight-for-age and height-for-age indexes, expressed as z scores by using the international reference population (15). Children were classified as stunted and underweight if their respective z scores were <2 SDs below the reference age and sex median.
During the follow-up, MRDR tests were taken by 20% of the children with the lowest baseline serum retinol concentrations because this group was more likely to respond to the intervention and because the limited amount of 3,4-didehydroretinyl acetate available to the investigators precluded administering the test to all of the children (16). Children were given a single 200-mL oral dose of 3,4-didehydroretinyl acetate dissolved in oil in the morning, and a single venous blood sample was drawn 5 h later. The MRDR test results were expressed as the ratio of 3,4-dehydroretinol concentrations from an administered dose, 5 h earlier, to circulatory retinol. The ratios were categorized according to the values of 0.06, with ratios 0.06 indicating inadequate retinol liver stores (16).
Biochemical analyses
Blood obtained by venipuncture (5 mL) was collected into evacuated tubes, slowly mixed, and allowed to stand for 15 min before centrifugation at 1530 x g for 15 min at room temperature to separate serum. The serum was separated into 2-mL cryotubes, wrapped in aluminum foil to minimize exposure to light, and placed in an ice chest containing dry ice. The specimens were transported daily from the collection site and placed in a freezer (-70°C) for 2 mo until they were sent packed in dry ice to Craft Technologies, Inc (Wilson, NC), where all biochemical analyses were conducted.
Vitamin A fortification
The concentration of fortificant used in this study was based on 1) the estimated intake of wheat-flour products and vitamin A by low-income groups in different ecologic regions, disaggregated by age group (17), and 2) expected nutrient losses due to usual conditions of milling, processing, storage, transport, and baking (18). Every 2 wk, ten 25-kg sacks of wheat flour were fortified with retinol palmitate (type 250 SD; Hoffmann-La Roche Ltd, Basel, Switzerland) at a concentration of 6 µg retinol equivalents (RE)/g flour at the Nutrition Center of the Philippines by using a ribbon blender. Previous tests showed that this level of fortification yields 2.2 µg RE/g pandesal as consumed (or, 133 µg RE/serving daily) after losses incurred during milling, processing, storage, transportation, and baking. This daily serving provides 33% of the Filipino RDA (400 µg RE) of vitamin A for children in the age group of our study population, an amount that is considered to be safe yet potentially efficacious in improving vitamin A status in populations with marginal-to-low or deficient status (19).
Two composite samples of fortified flour were obtained at the beginning and end of each batch-preparation cycle to monitor the stability and retention of vitamin A. Once fortified with vitamin A, the flour was returned to its coded sack. No vitamin A was added to the wheat flour used to bake the nonfortified pandesal given to the control group. The wheat flour was delivered in identical sacks to 2 small, school-based bakeries participating in the study (1 for each treatment group) to prevent contamination between the fortified and nonfortified breads. Pandesal was prepared daily according to standardized procedures (set by the Asian Baking Institute, Manila), packaged in color-coded bags, and given to the children 5 afternoons/wk for 30 wk. The feeding periods were supervised. Four days per week, pandesal was served with a teaspoon of peanut butter or coconut jam as a spread and ice water; on the remaining day, it was served plain with an artificially flavored drink. On the basis of label claims, the spreads and flavored drinks contained no ß-carotene or vitamin A. Daily consumption was recorded for each individual as relative amounts of the product served.
Statistical analysis
Data for normally distributed variables are reported as means ± SDs; data for nonnormally distributed variables are presented as medians with interquartile ranges (IQRs). Group entry characteristics were summarized and compared. Dietary intake of specific nutrients from all foods consumed by each child during the 24-h recall period, excluding the food provided by the intervention, was computed by using the Philippine food-composition tables (20). Changes in serum retinol concentrations were calculated by subtracting the value before the intervention from the value after the intervention, which are presented as means and 95% CIs. Differences between groups were examined by analysis of variance (ANOVA) or, for indexes with a nonnormal distribution, by the Mann-Whitney U test. We explored whether initial serum retinol concentrations (below or above the median) significantly modified the response to the intervention in a multiple regression model using an appropriate interaction term. Baseline serum retinol concentrations significantly modified the effect of the intervention; thus, subgroup analyses were performed. Logistic regression was performed on cutoffs recommended for the MRDR test to determine the relative odds of marginal vitamin A status by treatment group. Treatment codes were broken only after all bivariate and multivariate data analyses were completed. STATA 6.0 (StataCorp, College Station, TX) was used for all statistical calculations and a P value <0.05 was considered significant.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
. The vitamin A–fortified and nonvitamin A–fortified groups were well-balanced with respect to age and sex. Mean baseline serum retinol concentrations were comparable, although not low, in both groups: 1.17 ± 0.33 and 1.18 ± 0.30 µmol/L, respectively. Only 30 children (7.6%) from the vitamin A–fortified group and 22 children (5.0%) from the control group had low serum retinol concentrations (<0.70 µmol/L). Nearly 30% of children in each group had concentrations categorized as marginal (0.70–1.05 µmol/L). Hemoglobin concentrations were similar in the groups (
: 127 g/L), as was the prevalence of anemia (20%, ie, hemoglobin <120 g/L). Children were marginally nourished, as evidenced by average height-for-age z scores of –1.7 and –1.5 and weight-for-height z scores of –0.7 and –0.6 for the vitamin A–fortified and nonfortified groups, respectively. Recent morbidity and supplement use (Table 1), household income, parental educational level, and other socioeconomic and demographic variables (data not shown) were also similar at baseline between the 2 groups. There were no significant between- or within-group differences among the 83 children who had only an initial serum sample taken or among the 835 children who had both a baseline and follow-up sample (data not shown).
|
. Median baseline intakes of macro- and micronutrients were similar in both groups, with the reported vitamin A intake representing 40% of the Philippine RDA of 400 µg RE for this age group (21). Estimates of intake were 13% higher in the subsample of children who were assessed with the 3-d 24-h recalls. Median dietary vitamin A intake in this subsample was 163 µg RE (IQR: 96–252) and 181 µg RE (IQR: 104–268) for the vitamin A–fortified and nonfortified groups, respectively. Median nutrient intakes of the subjects did not change significantly between baseline and the 30-wk follow-up periods.
|
). These values indicate an 89% compliance rate. Compliance was affected most by occasional school absences rather than an inability to consume 60 g pandesal/d. Before carrying out subgroup analyses, we assessed the presence of an interaction effect between initial vitamin A status (above/below the median of 1.16 µmol/L) and response to fortification. The regression model including the interaction term, ie, the change in serum retinol concentration = ß0 (intercept) + ß1 (initial serum retinol category) + ß2 (treatment) + ß3 (treatment x initial serum retinol category) + 
yielded the following:
 |
.
|
|
). The shift in serum retinol concentrations was significantly greater in children from both groups who had low serum retinol (ie, <0.70 µmol/L) concentrations at baseline. Serum retinol in the initially deficient children in the fortified group increased by 0.13 µmol/L more than in the initially deficient nonfortified group, but this difference was not significant.
|
). When the ratio of 3,4-didehydroretinol to retinol was categorized according to the established cutoffs (ie, <0.06 and 0.06), the proportion of children with inadequate liver stores was almost twice as high in the nonfortified group than in the vitamin A–fortified group (28% and 15%; odds ratio: 0.45; 95% CI: 0.2, 1.0). Additionally, in this subsample of children, serum retinol concentrations changed by an average of 0.08 ± 0.053 µmol/L more in the vitamin A–fortified group than in the nonfortified group (Table 4
).
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Serum retinol concentrations improved as a result of vitamin A–fortified pandesal intake, with the largest change occurring in subjects with low baseline serum retinol concentrations. Vitamin A–fortified children with a low serum retinol concentration at baseline had a 0.13-µmol/L greater increase than did the nonfortified children. There was a significant interaction between baseline serum retinol values and the response to treatment. In the group of children whose baseline serum retinol values were below the median, serum retinol concentrations increased significantly more in the fortified than in the nonfortified children at the 30-wk follow-up (P = 0.02). There was no such effect in the group of children whose baseline serum concentrations were above the median. This improvement in serum retinol was mirrored by apparent improvement in liver stores of vitamin A as indicated by the MRDR test results in the subsample of children with marginal vitamin A status. The percentage of children in this subsample in whom the MRDR test results indicated inadequate liver vitamin A stores was 15.6% in the vitamin A–fortified group and 28.6% in the nonfortified group.
The high initial serum retinol concentrations and the low estimates of dietary vitamin A intake are noteworthy. Our intake estimates are similar to or higher than those obtained from several previous studies in Filipino children (13, 17); however, the initial serum retinol concentrations we measured are substantially higher than those reported elsewhere (18). Several factors may account for the high serum concentrations. First, the Philippines has implemented a highly successful vitamin A–supplementation program reaching >80% of all 1–4-y-olds semiannually since 1993 (22). More than half of our study children (those in grades 1–3) likely received high-dose vitamin A supplements during their preschool years. Second, there has been a general improvement in the nutritional status of Filipino children during the 1990s. Additionally, the low dietary vitamin A intakes indicate that this population may be at risk for vitamin A deficiency; however, intake data are not a direct or biological measure of vitamin A status, unlike serum retinol or the MRDR test.
The intake of pandesal in the present study was similar to estimated intakes of wheat-flour products from food consumption surveys in the Philippines. Florencio (17) estimated the average intake of wheat-flour products to be 46.7 ± 42.3, 64.8 ± 71.8, and 50.8 ± 51.8 g in their entire sample of preschool-age children and in pregnant and lactating women from economically depressed communities, respectively. Children in urban settings had average intakes that were higher than those used in the present trial. Similar results were found in school-age children in the Philippines, whose average intake of all wheat-flour products was 64.0 g/d (FS Solon, M Solon, L Sanchez, personal communication, 1997). Trends suggest that wheat consumption will continue to rise in the Philippines (12); therefore, fortification of wheat flour with vitamin A could have a beneficial effect on public health.
Wheat is the most widely produced cereal in the world, most of which is destined for human consumption. The processing of whole wheat to wheat flour is generally concentrated in a few large mills. The resulting flour is used to make bread, biscuits, pasta, and other products. Because of its widespread geographic distribution, acceptance, stability, and versatility, wheat flour can be a suitable vehicle for delivering vitamin A and other micronutrients to at-risk populations.
This is the first study that we are aware of that tested the efficacy of vitamin A fortification of wheat flour in a developing country. Our findings add important data to a growing base of evidence that food fortification can improve vitamin A status in populations in whom vitamin A deficiency is a public health problem. In the present study, the efficacy of a vitamin A–fortified staple was tested. Previous studies showed that fortification of condiments such as monosodium glutamate (10), sugar (8), and margarine (13) with vitamin A substantially improved vitamin A status. It is likely that vitamin A fortification as a strategy to improve vitamin A intake will be most efficacious if many different foods are fortified with modest amounts of vitamin A.
|
ACKNOWLEDGMENTS |
|---|
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONSUBJECTS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  L. W. Tengco, P. Rayco-Solon, J. A. Solon, J. N. Sarol Jr., and F. S. Solon Determinants of Anemia among Preschool Children in the Philippines J. Am. Coll. Nutr., April 1, 2008; 27(2): 229 - 243. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. A Tanumihardjo and B. A Underwood Utility of the relative-dose-response and modified-relative-dose-response tests as population indicators of vitamin A status Am. J. Clinical Nutrition, November 1, 2005; 82(5): 1135 - 1137. [Full Text] [PDF]
|
|
|
|
 |
|
 K. P. West Jr. Extent of Vitamin A Deficiency among Preschool Children and Women of Reproductive Age J. Nutr., September 1, 2002; 132(9): 2857S - 2866. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
) and nonfortified (
) groups by initial serum retinol concentration category [below (n = 210 fortified and 209 nonfortified) or above (n = 186 fortified and 230 nonfortified) the median of 1.16 µmol/L]. *Significantly different from the nonfortified group, P < 0.05.