Identifying areas with vitamin A deficiency: the validity of a semiquantitative food frequency method

Development of food lists as a first step to develop a food frequency questionnaire for toddlers in a multi-ethnic population

AIM

Toddlerhood is an important stage of growth, thus understanding the food intake of children in this age group is important. In Singapore, there is currently no simple tool, such as Food Frequency Questionnaire (FFQ), to collect dietary information from this ethnically diverse age group. Generating an appropriate food list is a crucial step in the development of a FFQ and this step is not clearly documented in the literature. The purpose of this study is to generate food lists and portion sizes for toddlers from three major ethnic groups in Singapore and document the processes involved in this first stage.

METHODS

A total of 30 mothers (equal number of Malays, Indians and Chinese) of 11-24-month-old children completed three-day food records and participated in the focus group discussion. The reported food items were then categorised into food groups.

RESULTS

The food lists varied by ethnic groups with the longest list obtained from Chinese toddlers. There were also other foods that were then classified as common foods for all ethnicities. Commonly used utensils among the three ethnic groups were small-sized bowls, plates, cups and spoons. For portion sizes, these utensils were typically half-filled for the toddlers.

CONCLUSIONS

As all Singaporeans have access to the same foods, the ethnic-specific food lists generated in this study could be combined into one list. Together with portion sizes, this information can be used for developing a semi-quantitative FFQ.

Assessment of vitamin A status of preschool children in a sub-Saharan African setting: comparative advantage of modified relative-dose response test

A nationally-representative sample of 2,696 preschool children living in Congo was examined during Au gust-September 2003 to determine the rates of vitamin A deficiency. Ninety clusters of 30 children, aged six months to six years, were selected, using a randomized two-level cluster-sampling method. Vitamin A deficiency was determined by assessing the prevalence of active xerophthalmia (nightblindness and/or Bitot spots) in the cross-over sample of 2,696 individuals. A semi-quantitative seven-day dietary questionnaire was concurrently applied to the mothers of children enrolled to estimate the latter's consumption of vitamin A-rich food. Vitamin A status was assessed by performing the modified relative dose-response test (MRDR) on dried blood spots (DBS) from a subsample of 207 children aged less than six years and the impression cytology with transfer (ICT) test on a subsample of 1,162 children. Of the children enrolled, 5.2% suffered from nightblindness, 8.0% had Bitot spots, and 2.5% had other vitamin A deficiency sequellae. Fifty-three percent of the ICT tests showed the presence of vitamin A deficiency. The biochemical MRDR test showed that the vitamin A status of 30% of the study children was critical. Twenty-seven of them had retinol levels of < 10 microg/dL [mean +/- standard deviation (SD) 7.02 +/- 2.0 microg/dL], and 50% had retinol levels of 10-20 microg/dL (mean +/- SD 14.2 +/- 2.83 microg/dL). The poor health status and low rates of consumption of vitamin A-rich food are the main factors determining critical status. Vitamin A deficiency, reflecting poor nutrition and health, is a serious public-health issue among children aged less than six years in Congo.

Food-frequency questionnaires: a review of their design, validation and utilisation

A review of the literature concerning the design, utilisation and validation of food-frequency questionnaires (FFQ) has been carried out using a semi-systematic approach to obtaining, reviewing and extracting data from articles. Databases were searched from 1980 to 1999. The present review identified 227 validation (from 1980 to September 1999) and 164 utilisation (for 1998 only) studies. A number of design issues have been evaluated through the present review. These include: the need to consider how portion sizes have been described, self-defined giving higher mean correlations; how an FFQ was administered, interviewer-administered giving higher mean correlations for some nutrients; how many items to include on an FFQ, those with the largest number of items having higher correlations. Validation techniques were described. Most validation studies involved comparing an FFQ against another dietary assessment method; only 19 % compared an FFQ to a biomarker. Measurement differences were most commonly assessed by correlation coefficients as opposed to other more appropriate methods. Mean correlation coefficients were highest for Ca and fat, and lowest for vitamin A and vegetables. The utilisation studies showed that FFQ were most commonly used in cross-sectional surveys, with ninety-three of the FFQ being designed to be disease-specific. The present review results were presented to a group of experts and a consensus arrived at concerning the development, validation and use of FFQ. Recommendations derived from the consensus arising from the literature review are presented as an appendix to the present paper.

Vitamin A status among children in China

Objective

The objective of this study was to assess the prevalence of vitamin A deficiency (VAD) in children under 6 years old in China and to identify risk groups for VAD.

Design

A cross-sectional survey was conducted in 14 provinces from coastal, inland and western geographic areas in China.

Setting

One city (urban) and two counties (rural) were randomly selected from each province as survey areas.

Subjects

About 200 children aged 0–6 years were randomly selected in each survey area. A blood sample was collected from each child. Data on sociodemographics and nutrition were obtained by interview of the mother or principal caregiver. Fluorescence microanalysis was used to analyse serum retinol concentration.

Results

VAD (serum retinol < 0.7 μmol l− 1) was observed in 957 out of 7826 children aged 0–6 years (12.2% of the entire study population), whereas severe VAD (serum retinol < 0.35 μmol l− 1) was found in 39 children (0.5%). The highest prevalences of VAD at >1 year of age were observed among children of mothers with minority ethnicity (22.7%) or poor education (19.8%) and in the poor western area (17.4%).

Conclusions

VAD is a nutritional problem in children in China. Children living in the poor western area, having a mother with minority ethnicity or a mother with poor education have a high risk of VAD.

Prevalence of infant Vitamin A deficiency and undernutrition in the Republic of Congo

OBJECTIVES

A representative sample of 5722 pre-school children living in rural and urban areas of the Congo was examined between July and September 1999 for assessing Vitamin A deficiency.

METHODS

Using a randomized two-level cluster sampling method, 190 clusters of 30 children aged from 6 months to 6 years were selected in order to assess the prevalence of active xerophthalmia (night blindness and/or Bitot spots). Concurrently, the children's height and weight were determined. A semi-quantitative seven-day dietary questionnaire was applied to the mothers of 5722 children to estimate the latter's consumption of Vitamin A rich foodstuffs. The prevalence of biochemical deficiency was assessed based on the serum retinol concentrations analyzed in dried blood spots from a sub-sample of 300 children living in the Pointe-Noire area.

RESULTS

Among the 5722 children studied, 0.7% were found to suffer from night blindness and 7.7% had Bitot spots. The weekly intake of Vitamin A rich foods was estimated in 5722 children. Our data suggest that Vitamin A rich food consumption was lower in rural zones than in urban area according to the food frequency method threshold values. The serum retinol levels were lower than 10 microg/dl in 18% (95% confidence interval [C.I.]: 13.7, 22.3) [8.04+/-2.87 microg/dl] and less than 20 microg/dl in 49% (95% C.I.: 43.4, 54.6) [15.05+/-2.76 microg/dl] of the 300 studied children. We have established a significant relation between mean serum retinol levels and high rate of Vitamin A food intake (chi-square=59.64, 2 d.d.l., p<0.05) in the sample studied. The mean serum retinol concentrations did not differ significantly between the various Z-scores of weight for age (W/A) and height for age (H/A) patterns. But children with a weight for height (W/H) ratio below -2 standard deviation (S.D.) had significantly lower serum retinol values [9.33+/-1.3 microg/dl] than those with a W/H ratio greater than or equal to -2S.D. [10.82+/-4.84 microg/dl].

CONCLUSION

These data suggest that Vitamin A deficiency is still a serious public health problem in rural areas of the Congo in which this study was carried out.

Consumption of Vitamin A by Breastfeeding Children in Rural Kenya

Vitamin A deficiency remains a significant health risk in developing countries, affecting infants and children in particular. To counter child malnutrition, mothers are encouraged to breastfeed to ensure that their children receive adequate macro- and micronutrients, including vitamin A. However, this assumes that the mother has sufficient vitamin A intake to provide enough vitamin A to her child. This study investigates maternal and infant intakes of locally available foods of high vitamin A content in a rural agricultural community in Kenya. The study aims to establish the community risk for vitamin A deficiency and to assess whether breast milk is adequate to maintain and build retinol reserves of the breastfed infant. The study assesses 62 mother-child pairs and employs several methods to support its objectives, including the Helen Keller International food-frequency survey, maternal and infant anthropometric measurements, and maternal breast-milk and blood samples to determine breast-milk and serum retinol levels. We found that mothers with marginal (< 0.700 μmol/l) serum retinol and breast-milk deficient (< 1.05 μmol/l) in retinol accounted for 45.2% and 77.4%, of our sample, respectively. A significant (p < 0.05) proportion (40.3%) of mothers had breast milk deficient in retinol and marginal levels of serum retinol. The risk of vitamin A deficiency in breastfed infants older than six months was high, because 89.5% of them did not consume foods high in vitamin A content three times weekly. The primary source of vitamin A for infants younger than six months was breast-milk deficient in retinol vitamin A. This study suggests that in this rural community, breastfed infants may not receive appropriate foods with high vitamin A content and that although exclusive breastfeeding is advocated, most breast milk is deficient in retinol, further heightening the risk of vitamin A deficiency.

Development of a rapid enzyme immunoassay for the detection of retinol-binding protein

BACKGROUND

Retinol-binding protein (RBP) was chosen as a surrogate marker for retinol because of the close correspondence between retinol and RBP.

OBJECTIVE

To meet the need for rapid, cost-effective determination of vitamin A status in populations, a quantitative enzyme immunoassay (EIA) for detection of RBP was developed.

DESIGN

The resulting RBP EIA, a competitive assay, uses RBP adsorbed to microtest strip wells to compete with RBP in serum. The assay takes approximately 40 min.

RESULTS

With a reference panel of sera, test accuracy was found to be within 4% of expected values through the calibrated range of 0.48-1.92 micro mol RBP/L (10-40 micro g RBP/mL). Intraassay and interassay variability averaged 6.7% and 8.9%, respectively. Specificity testing showed no interference from other serum proteins, prealbumin, rheumatoid factor, bilirubin, estrogen, or C-reactive protein. The RBP EIA provided linear results between 0.43 and 1.80 micro mol RBP/L (9 and 38 micro g RBP/mL). Preliminary laboratory evaluations indicated that the RBP EIA correlates well with radial immunodiffusion for RBP and with HPLC for retinol, the current reference standard. A field evaluation in a population at risk for vitamin A deficiency (VAD) resulted in close correlation between RBP EIA measures and retinol measures by HPLC (R(2) = 0.82).

CONCLUSIONS

The RBP EIA is as reliable in estimating VAD as is HPLC retinol. After successful validations, the test should enable public health authorities to rapidly monitor VAD and track vitamin A status in populations.

Validation of the second version of a quantitative food-frequency questionnaire for use in Western Mali

OBJECTIVE

To assess the relative validity of the second version of a quantitative food-frequency questionnaire (QFFQ), designed to measure the habitual food and nutrient intake in one season in rural populations in Western Mali, West Africa.

DESIGN

The dietary intake during the previous week was assessed with the 164-item QFFQ administered by interview. This was compared with the intake from a 2-day weighed record (WR) with weighed recipes.

SETTING

The village of Ouassala in the Kayes region, Western Mali.

SUBJECTS

Thirty-four women and 36 men aged 15-45 years, from 29 households.

RESULTS

The QFFQ gave a lower intake of lunch and dinner and a higher intake of snacks than the WR. The discrepancies were larger for women than for men. The median proportion of subjects classified in the same quartile of intake was 29% for food groups and 36% for energy and nutrients. For classification into extreme opposite quartiles, the median proportion was 6% for food groups and 7% for energy and nutrients. Spearman's rank correlation for energy and nutrients ranged from 0.16 (% energy from protein) to 0.62 (retinol equivalents).

CONCLUSIONS

The second version of the QFFQ tends to underestimate total food weight. The methods used for estimating food portion size should therefore be applied with caution. The changes made from the first version had little effect. The ability to rank subjects according to dietary intake is similar with both versions. The improved layout of the new QFFQ makes it a more user-friendly tool for comparing dietary intake between population groups and for measuring changes over time.

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

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.

Urbanisation and vitamin A deficiency in children: comparison between a traditional district and a new settlement in Mali

OBJECTIVES

The purpose of this study was to assess the vitamin A status of pre-school urban children and to compare the situation between a traditional district and a new settlement after two decades of intense urbanisation.

SUBJECTS AND METHODS

A cross-sectional stratified survey was carried out in Bamako, Mali, on a representative sample of children (aged 4-6 years). 532 children were involved from a traditional district and 453 from a new settlement (NS). The vitamin A status was assessed by: clinical indicators (ophthalmic examination), subclinical indicators (questionnaire looking for night blindness, impression cytology with transfer test (ICT), modified relative dose response test (MRDR), and a diet inquiry about vitamin A intakes. Acute malnutrition was assessed by a weight/height measure.

RESULTS

In both districts, all the clinical indicators were below the WHO criteria that define a public health problem. Both the ICT test, respectively 19 and 21% of abnormal tests, and the MRDR, 67.3 and 73.1% of tests > or = 0.06, indicated a subclinical vitamin A deficiency as defined by WHO thresholds. During the preceding week only four children in NS had consumed vitamin A-rich food less than seven times. No significant difference between the two districts was found either for clinical or subclinical indicators (p > 0.5).

CONCLUSION

Despite a rapid urbanisation, the vitamin A status of the children seemed to be rather homogeneous among the different districts. The population remained vulnerable with peripheral depletion and low hepatic stores of vitamin A. The urban children should be carefully monitored regarding vitamin A status.

What Are Preschool Children Eating? A Review of Dietary Assessment

Accurate assessment of dietary intake among preschool-aged children is important for clinical care and research, for nutrition monitoring and evaluating nutrition interventions, and for epidemiologic research. We identified 25 studies published between January 1976 and August 2000 that evaluated the validity of food recalls (n = 12), food frequency questionnaires (n = 9), food records (n = 2), or other methods (n = 2). We identified four studies that evaluated the reproducibility of food frequency questionnaires. Validity studies varied in validation standard and study design, making comparisons between studies difficult. In general, food frequency questionnaires overestimated total energy intake and were better at ranking, than quantifying, nutrient intake. Compared with the validation standard, food recalls both overestimated and underestimated energy intake. When choosing a method to estimate diet, both purpose of the assessment and practicality of the method must be considered, in addition to the validity and reproducibility reported in the scientific literature.

Dietary vitamin A intakes of preschool-age children in South India

The vitamin A intake of children aged 1-3 y (n = 683) was assessed using a quantitative food-frequency questionnaire in a vitamin A intervention study in South India. Trained field workers interviewed mothers about their children's usual consumption of common sources of vitamin A and collected information on portion sizes using standard cups. Mothers were asked to state the number of months in a year during which specific seasonal foods were available. Information about current breast-feeding was also obtained. Vitamin A intakes from nonbreast milk sources were extremely low at all ages. The median intake of total vitamin A, beta-carotene and retinol was 121, 100 and 21 retinol equivalents (RE), respectively. Maternal education and socioeconomic status (SES) were positively associated with total vitamin A and retinol intakes. Girls had significantly lower intakes than boys even after adjusting for differences in age, maternal education, SES and breast-feeding status. Breast-feeding was common, but declined to 60% by 24 mo and to 15% by 36 mo. Vitamin A intakes from nonbreast milk sources increased with age only for currently breast-fed children, who tended to be of lower SES. After taking into account the potential contribution of breast milk by using published estimates, nonbreast-fed children met only 60% of the Indian recommended dietary allowance (RDA; 250 RE/d), whereas breast-fed children met approximately 90% of the RDA during y 2 of life.

Rationale and design of the Tanzania Vitamin and HIV Infection Trial

We present the rationale and design of a randomized, double-blind, placebo-controlled trial of vitamin supplements among HIV-positive pregnant women in Dar es Salaam, Tanzania. Higher levels of intake of vitamins A, B, C, and E may decrease the risk of vertical transmission and progression of HIV infection by enhancing maternal and infant immune function; by reducing viral load in the blood, breast milk, or lower genital tract secretions; and/or by strengthening the placental barrier to infection. Eligible pregnant women were randomized to receive vitamin A, multivitamins excluding A, vitamin A and multivitamins, or placebo. The main endpoints include vertical transmission of HIV infection, as assessed by examination of infection in infants using polymerase chain reaction (PCR), and progression of HIV disease as measured by the WHO clinical staging system. Over a period of 2 years, 13,876 women were tested for HIV infection, with appropriate pre- and posttest counseling, to enroll 1085 consenting HIV-positive women. The trial assesses women and their children once a month for a minimum of 18 months after delivery or up to the end of this 5-year study. We examine recruitment strategies and means of enhancing cohort retention in long-term follow-up. We assess compliance with the use of supplements by direct questioning, by counting pills, and biochemically by using serum beta-carotene and urine riboflavin levels. Briefly, we discuss ethical issues related to the conduct of AIDS prevention trials in this setting. In sub-Saharan Africa, most HIV-infected persons lack access to the relevant antiretroviral and prophylactic drugs, and the region urgently needs low-cost treatments and preventive strategies. The Tanzania trial should provide valuable data to address the effect of vitamin supplements in the transmission and progression of HIV infection.

The Helen Keller International Food-Frequency Method Underestimates Vitamin A Intake Where Sustained Breastfeeding is Common

A recent innovation in assessing community vitamin A status is the Helen Keller International food-frequency method, which is based on weekly intakes of key foods among pre-school children. Since it excludes breastmilk, we investigated whether the amount of breastmilk received by 40 children aged one to three years in a rural area of Bangladesh contributed significantly to their vitamin A intake. Vitamin A intake was indirectly calculated from the consumption of breastmilk, which was quantified over a 9-hour period by a test-weighing technique. The estimated mean 24-hour milk intake was 548 g for the 97% who were breastfed at 12 to 23 months and 312 g for the 73% who were breastfed at 24 to 36 months. This represents an average daily intake of 41% and 23% of the safe recommended daily intake (400 RE) for vitamin A, respectively. The Helen Keller International food-frequency method should be revalidated for settings where breastfeeding is sustained beyond infancy.