Vitamin D deficiency is associated with high prevalence of diabetes in Kuwaiti adults: results from a national survey.

BACKGROUND: Vitamin D homeostasis may play a critical role in glucose metabolism. Little is known on vitamin D deficiency and its association with diabetes in countries of the Arabia Gulf where the population is experiencing a rapid increase in the incidence of diabetes. METHODS: In a cross-sectional study of 960 adults enrolled in the first National Nutrition Survey of the State of Kuwait (NNSSK), we examined vitamin D status in association with the prevalence of diabetes and prediabetes. Vitamin D status was measured by serum levels of 25-hydroxyvitami D (25(OH)D). Prevalences of diabetes and prediabetes were determined based on fasting glucose and HbA1C levels. RESULTS: The median level of serum 25(OH)D in Kuwaiti adults was 13.8 ng/ml. Approximately 56 % of the Kuwaiti adults had vitamin D inadequacy (25(OH)D = 12-19.9 ng/ml), and 27 % had vitamin D deficiency (25(OH)D < 12 ng/ml). The prevalences of prediabetes and diabetes were 40 and 27 %, respectively. Vitamin D inadequacy (OR = 1.7, 95 % CI: 1.0-2.9) and deficiency (OR =2.0, 95 % CI: 1.1-3.3) was each associated with about two-fold increased odds of prediabetes compared to sufficient vitamin D status (25(OH)D ≥ 20 ng/ml). Vitamin D inadequacy (OR =2.1, 95 % CI: 1.2-3.7) and deficiency (OR =2.0, 95 % CI: 1.1-3.9) were also associated with two-fold increased odds of diabetes. CONCLUSIONS: Data from Kuwaiti's first nutrition nutritional survey suggests a very high prevalence of vitamin D deficiency in Kuwaiti adults. Associations of low vitamin D status and high prevalence of diabetes point to the need of continuous monitoring of vitamin D status and further evaluating potential health consequences in this high-risk population.

Effectiveness Study of Paromomycin IM Injection (PMIM) for the Treatment of Visceral Leishmaniasis (VL) in Bangladesh.

BACKGROUND: This study was conducted in Bangladeshi patients in an outpatient setting to support registration of Paromomycin Intramuscular Injection (PMIM) as a low-cost treatment option in Bangladesh. METHODOLOGY: This Phase IIIb, open-label, multi-center, single-arm trial assessed the efficacy and safety of PMIM administered at 11 mg/kg (paromomycin base) intramuscularly once daily for 21 consecutive days to children and adults with VL in a rural outpatient setting in Bangladesh. Patients ≥5 and ≤55 years were eligible if they had signs and symptoms of VL (intermittent fever, weight loss/decreased appetite, and enlarged spleen), positive rK39 test, and were living in VL-endemic areas. Compliance was the percentage of enrolled patients who received 21 daily injections over no more than 22 days. Efficacy was evaluated by initial clinical response, defined as resolution of fever and reduction of splenomegaly at end of treatment, and final clinical response, defined as the absence of new clinical signs and symptoms of VL 6 months after end of treatment. Safety was assessed by evaluation of adverse events. PRINCIPAL FINDINGS: A total of 120 subjects (49% pediatric) were enrolled. Treatment compliance was 98.3%. Initial clinical response in the Intent-to-Treat population was 98.3%, and final clinical response 6 months after end of treatment was 94.2%. Of the 119 subjects who received ≥1 dose of PMIM, 28.6% reported at least one adverse event. Injection site pain was the most commonly reported adverse event. Reversible renal impairment and/or hearing loss were reported in 2 subjects. CONCLUSIONS/SIGNIFICANCE: PMIM was an effective and safe treatment for VL in Bangladesh. The short treatment duration and lower cost of PMIM compared with other treatment options may make this drug a preferred treatment to be investigated as part of a combination therapy regimen. This study supports the registration of PMIM for use in government health facilities in Bangladesh. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01328457.

The effects of daily consumption of ß-cryptoxanthin-rich tangerines and ß-carotene-rich sweet potatoes on vitamin A and carotenoid concentrations in plasma and breast milk of Bangladeshi women with low vitamin A status in a randomized controlled trial.

BACKGROUND: The potential of ß-cryptoxanthin (CX)-rich foods to form vitamin A (VA) in humans in not well understood. OBJECTIVE: We measured the effects of consuming CX- and ß-carotene (BC)-rich foods on plasma and breast milk VA and carotenoids in lactating women with low VA status. DESIGN: Participants were randomly assigned to 4 groups (n = 34, 34, 34, and 33, respectively) receiving orange-fleshed sweet potatoes (OFSPs) (12 mg BC/d), tangerines (5.3 mg CX/d), white-fleshed sweet potatoes (WFSPs) with a VA supplement (0.5 mg/d), or WFSPs 2 times/d, 6 d/wk for 3 wk. All except the VA group received placebo capsules identical in appearance to VA supplements. Changes in plasma and breast milk VA, BC, and CX were measured. RESULTS: Plasma retinol increased in the VA group. Plasma BC in the OFSP group and CX in the tangerine group increased 250% and 830%, respectively; apparent relative absorption in the CX group, considering the amounts consumed, was 4 times that in the BC group. Mean (±SEM) changes in milk VA in the OFSP (0.028 ± 0.074 µmol/L) and tangerine (0.067 ± 0.091 µmol/L) groups did not differ from those in the control (-0.077 ± 0.068 µmol/L) or VA (0.277 ± 0.094 µmol/L) group. Milk CX increased in the tangerine group. CONCLUSIONS: VA capsules increased plasma and milk VA concentrations. The greater change in CX concentrations in the tangerine group than in BC concentrations in the OFSP group suggests that CX in tangerines was better absorbed, but both foods failed to increase milk VA concentrations. This trial was registered at clinicaltrials.gov as NCT01420406.

Very low adequacy of micronutrient intakes by young children and women in rural Bangladesh is primarily explained by low food intake and limited diversity.

Documentation of micronutrient intake inadequacies among developing country populations is important for planning interventions to control micronutrient deficiencies. The objective of this study was to quantify micronutrient intakes by young children and their primary female caregivers in rural Bangladesh. We measured 24-h dietary intakes on 2 nonconsecutive days in a representative sample of 480 children (ages 24-48 mo) and women in 2 subdistricts of northern Bangladesh by using 12-h weighed food records and subsequent 12-h recall in homes. We calculated the probability of adequacy (PA) of usual intakes of 11 micronutrients and an overall mean PA, and evaluated dietary diversity by counting the total number of 9 food groups consumed. The overall adequacy of micronutrient intakes was compared to dietary diversity scores using correlation and multivariate regression analyses. The overall mean prevalence of adequacy of micronutrient intakes for children was 43% and for women was 26%. For children, the prevalence of adequate intakes for each of the 11 micronutrients ranged from a mean of 0 for calcium to 95% for vitamin B-6 and was <50% for iron, calcium, riboflavin, folate, and vitamin B-12. For women, mean or median adequacy was <50% for all nutrients except vitamin B-6 and niacin and was <1% for calcium, vitamin A, riboflavin, folate, and vitamin B-12. The mean PA (MPA) was correlated with energy intake and dietary diversity, and multivariate models including these variables explained 71-76% of the variance in MPA. The degree of micronutrient inadequacy among young children and women in rural Bangladesh is alarming and is primarily explained by diets low in energy and little diversity of foods.

Daily consumption of orange-fleshed sweet potato for 60 days increased plasma ß-carotene concentration but did not increase total body vitamin A pool size in Bangladeshi women.

We assessed the effect of daily consumption of orange-fleshed sweet potatoes (OFSP), with or without added fat, on the vitamin A (VA) status of Bangladeshi women with low initial VA status. Women (n = 30/group) received one of the following for 6 d/wk over 10 wk: 1) 0 µg retinol activity equivalents (RAE)/d as boiled white-fleshed sweet potatoes (WFSP) and a corn oil capsule, 2) 600 µg RAE/d as boiled OFSP and a corn oil capsule, 3) fried OFSP and a corn oil capsule, or 4) boiled WFSP and a retinyl palmitate capsule in addition to their home diets. Plasma concentrations of retinol and ß-carotene and total body VA pool size were assessed before and after the 60-d intervention. Initial and final plasma retinol concentrations (mean ± SD) were 0.75 ± 0.18 µmol/L and 0.84 ± 0.19 µmol/L, respectively (P = 0.31); final means did not differ by group. Initial and final plasma ß-carotene concentrations were 0.10 ± 00 µmol/L and 0.18 ± 0.09 µmol/L, respectively (P < 0.0001); final mean plasma ß-carotene concentrations were higher in groups that received OFSP (P < 0.0001), and final mean plasma ß-carotene was marginally higher in the group that received fried OFSP compared with boiled OFSP (P = 0.07). Initial and final total body VA pool sizes were 0.060 ± 0.047 mmol and 0.091 ± 0.070 mmol, respectively (P = 0.05, n = 110) and did not differ by group. Despite an increase in plasma ß-carotene concentration, the impact of OFSP on VA status appears to be limited in Bangladeshi women residing in a resource-poor community.

Short communication: evaluation of a new rapid diagnostic test for quality assurance by kala azar elimination programme in bangladesh.

In Bangladesh, serological tests have been widely used for the primary screening of visceral leishmaniasis (VL). Several serologic tests are available for the diagnosis of VL. Selection of the best test is important to permit diagnostic differentiation between symptomatic and asymptomatic patients and to reduce cross-reactivity. We evaluated the effectiveness of a new serological test "Onsite Leishmania Ab Rapid Test" as a part of "quality assurance" activities for the kala azar elimination programme of the Government of Bangladesh. Plasma samples of 100 parasitologically confirmed cases of VL along with 101 healthy controls were tested, and "Onsite Leishmania Ab Rapid Test" strip tests were positive in 94 out of 100 confirmed VL cases, whereas four out of 51 healthy subjects from the VL endemic areas also tested positive. All the 50 healthy volunteers tested negative. Thus, the sensitivity and specificity of "Onsite Leishmania Ab Rapid Test" strip test were found to be 94% (95% CI: 87-98) and 96% (95% CI: 90-99), respectively. This study showed that the performance of the "Onsite Leishmania Ab Rapid Test" strip tests was up to the recommended level.

Intakes and breast-milk concentrations of essential fatty acids are low among Bangladeshi women with 24-48-month-old children.

Maternal fat intake and adipose reserves are major sources of PUFA during lactation. The present study examined the cross-sectional relationship between prolonged breast-feeding and maternal BMI, assessed adequacy of fat intake among lactating and non-lactating mothers of children 24-48 months of age and determined breast-milk fatty acid composition. Multi-stage sampling was used to select a representative sample of mothers from two rural districts in Bangladesh (n 474). Dietary data were collected during two non-consecutive 24 h periods via 12 h in-home daytime observations and recall. The National Cancer Institute method for episodically consumed foods was used to estimate usual intake distributions. Breast milk samples were collected from ninety-eight women, and breast-milk fatty acid methyl esters were quantified using GC. Approximately 42 % of lactating v. 26 % of non-lactating mothers were underweight (BMI < 18·5 kg/m2; P = 0·0003). The maternal diet was low in total fat (approximately 8 % of mean total energy) and food sources of PUFA, including oil and animal source foods, resulting in a low estimated mean total consumption of PUFA (5·1 g/d). Almost all women were estimated to consume less than the recommended intake levels for total fat, total PUFA, α-linolenic acid (ALA) and DHA. Median breast-milk linoleic acid (8·5 % weight) and ALA (0·2 %) concentrations were among the lowest reported in the literature, in contrast with arachidonic acid (0·5 %) and DHA (0·3 %) concentrations, which were mid-range. Bangladeshi women in general, and especially those who practise prolonged breast-feeding, may benefit from increased consumption of food sources of PUFA.

Dietary intake of polyunsaturated fatty acids among breast-feeding and non-breast-feeding 24- to 48-month-old children in Bangladesh.

OBJECTIVE: The aim of the study was to assess the adequacy of polyunsaturated fatty acid intake by rural Bangladeshi children 24 to 48 months old in relation to their breast-feeding status. MATERIALS AND METHODS: Multistage sampling was used to select a representative sample of children 24 to 48 months of age from 2 rural districts in Bangladesh (n = 479). Two nonconsecutive 24-hour periods of dietary data were collected via 12-hour daytime in-home observations and recall. Breast milk intake was estimated using test weighing. The National Cancer Institute (NCI) method for episodically consumed foods was used to estimate distributions of usual food and nutrient intakes. RESULTS: Based on the estimated intake distributions, >95% of the children had usual fat intakes <30% of total energy. Among 24- to 35-month-old (younger) and 36- to 48-month-old (older) children, respectively, 4% and 16% of breast-feeding children and 31% and 41% of non-breast-feeding children were estimated to consume <10% of total energy from fat. An estimated 80% of all of the children consumed <4% of total energy as linoleic acid, and 99% consumed <1% of energy as α-linolenic acid. Younger breast-feeding children had higher estimated average docosahexaenoic acid (DHA) intakes (0.04 g DHA/day) than their non-breast-feeding counterparts (0.01 g DHA/day; P = 0.0005). Both breast-feeding and non-breast-feeding older children had estimated mean DHA intakes of 0.02 g/day (P = 0.74). CONCLUSIONS: Rural Bangladeshi children 24 to 48 months old, and especially those who have discontinued breast-feeding, may benefit from increased fat consumption.

The paired deuterated retinol dilution technique can be used to estimate the daily vitamin A intake required to maintain a targeted whole body vitamin A pool size in men.

The estimated average requirement (EAR) for vitamin A (VA) of adult males is based on the amount of dietary VA required to maintain adequate function and provide a modest liver VA reserve (0.07 µmol/g). In the present study, the paired-deuterated retinol dilution technique was used to estimate changes in VA pool size in Bangladeshi men from low-income, urban neighborhoods who had small initial VA pool sizes (0.059 ± 0.032 mmol, or 0.047 ± 0.025 µmol/g liver; n = 16). The men were supplemented for 60 d with 1 of 8 different levels of dietary VA, ranging from 100 to 2300 µg/d (2 men/dietary VA level). VA pool size was estimated before and after the supplementation period. The mean change (plus or minus) in VA pool size in the men was plotted against their corresponding levels of daily VA intake and a regression line was fit to the data. The level of intake at which the regression line crossed the x-axis (where estimates of VA pool size remained unchanged) was used as an estimate of the EAR. A VA intake of 254-400 µg/d was sufficient to maintain a small VA pool size (0.059 ± 0.032 mmol) in the Bangladeshi men, corresponding to a VA intake of 362-571 µg/d for a 70-kg U.S. man, which is lower than their current EAR of 625 µg/d. The data suggest that the paired-deuterated retinol dilution technique could be used for estimating the EAR for VA for population subgroups for which there are currently no direct estimates.

Evaluation of rK-39 strip test using urine for diagnosis of visceral leishmaniasis in an endemic area in Bangladesh.

Diagnosis of visceral leishmaniasis (VL) by demonstration of parasites in tissue smears obtained from bone marrow, spleen or lymph nodes is risky, painful, and difficult. The rK-39 strip test is widely used for the diagnosis of VL using blood/serum samples in endemic countries. The aim of the study was to evaluate the rK-39 strip test using urine sample as a non-invasive means for the diagnosis of VL. The rk-39 strip test was performed using urine from 100 suspected VL cases along with 25 disease control (malarial febrile cases) and 50 healthy control (from endemic and non-endemic areas). All the VL suspected cases were positive with the rK-39 strip test using serum. The sensitivity and specificity of the rK-39 strip test using urine samples was 95% and 93.3%, respectively, compared to serum based rK-39 test. The findings suggest that the urine based rK-39 test could be a practical and efficient tool for the diagnosis of VL patients in rural areas, particularly where resources are limited.

The current high prevalence of dietary zinc inadequacy among children and women in rural Bangladesh could be substantially ameliorated by zinc biofortification of rice.

Rural Bangladeshi populations have a high risk of zinc deficiency due to their consumption of a predominantly rice-based diet with few animal-source foods. Breeding rice for higher zinc content would offer a sustainable approach to increase the population's zinc intakes. The objectives of the study were to quantify usual rice and zinc intakes in young children and their adult female primary caregivers and to simulate the potential impact of zinc-biofortified rice on their zinc intakes. We measured dietary intake in a representative sample of 480 children (ages 24-48 mo) and their female caregivers residing in 2 rural districts of northern Bangladesh. Dietary intakes were estimated by 12-h weighed records and 12-h recall in homes on 2 nonconsecutive days. Serum zinc concentrations were determined in a subsample of children. The median (25th, 75th percentile) rice intakes of children and female caregivers were 134 (99, 172) and 420 (365, 476) g raw weight/d, respectively. The median zinc intakes were 2.5 (2.1, 2.9) and 5.4 (4.8, 6.1) mg/d in children and women, respectively. Twenty-four percent of children had low serum zinc concentrations ( < 9.9 micromol/L) after adjusting for elevated acute phase proteins. Rice was the main source of zinc intake, providing 49 and 69% of dietary zinc to children and women, respectively. The prevalence of inadequate zinc intakes was high in both the children (22%) and women (73-100%). Simulated increases in rice zinc content to levels currently achievable through selective breeding decreased the estimated prevalence of inadequacy to 9% in children and 20-85% in women, depending on the assumptions used to estimate absorption. Rural Bangladeshi children and women have inadequate intakes of zinc. Zinc biofortification of rice has the potential to markedly improve the zinc adequacy of their diets.

Experience in managing severe malnutrition in a government tertiary treatment facility in Bangladesh.

Children with severe acute malnutrition, defined as weight-for-height <70% of the reference median or bilateral pedal oedema or mid-arm circumference <110 mm having complications, were managed in the Nutrition Unit of the Chittagong Medical College Hospital (CMCH) following the guidelines of the World Health Organization, with support from Concern Worldwide Bangladesh and ICDDR,B. In total, 171 children aged less than five years (mean +/- SD age 23.5 +/- 15.3 months) were admitted during June 2005-May 2006. Of them, 66% were aged less than two years, and 84.2% belonged to households with a monthly income of less than US$ 40. The main reason for bringing children by their families to the hospital was associated major illnesses: bronchopneumonia (33%), oedema (24%), diarrhoea (11%), pulmonary tuberculosis (9%), or other conditions, such as meningitis, septicaemia, and infections of the skin, eye, or ear. The exit criteria from the Nutrition Unit were: (a) for children admitted without oedema, an absolute weight gain of > or = 500 and > or = 700 g for children aged less than two years and 2-5 years respectively; and for children admitted with oedema, complete loss of oedema and weight-for-height >70% of the reference median, and (b) the mother or caretaker has received specific training on appropriate feeding and was motivated to follow the advice given. Of all the admitted children, 7.6% of parents insisted for discharging their children early due to other urgent commitments while 11.7% simply left with their children against medical advice. Of the 138 remaining children, 88% successfully graduated from the Nutrition Unit with a mean weight gain of 10.6 g/kg per day (non-oedematous children) and loss of -1.9 g/kg per day (oedematous children), 86% graduated in less than three weeks, and the case-fatality rate was 10.8%. The Nutrition Unit of CMCH also functions as a training centre, and 197 health functionaries (82 medical students, 103 medical interns, and 12 nurses) received hands-on training on management of severe malnutrition. The average cost of overall treatment was US$ 14.6 per child or approximately US$ 1 per child-day (excluding staff-cost). Food and medicines accounted for 42% and 58% of the total cost respectively. This study demonstrated the potential of addressing severe acute malnutrition (with complications) effectively with minimum incremental expenditure in Bangladesh. This public-private approach should be used for treating severe acute malnutrition in all healthcare facilities and the treatment protocol included in the medical and nursing curricula.

Sweet potato beta-carotene bioefficacy is enhanced by dietary fat and not reduced by soluble fiber intake in Mongolian gerbils.

Orange-fleshed sweet potato (OFSP) is an important source of beta-carotene (betaC). Provitamin A bioefficacy from plant foods is influenced by dietary fat and fiber. We fed 3% OFSP powder diets with varying amounts of fat and soluble fiber to vitamin A (VA)-depleted Mongolian gerbils (n = 85) for 3 wk (8 groups, n = 10/group; control, n = 9) following a baseline kill (n = 6). OFSP diets differing in fat (3, 6, and 12%) contained 0.24% soluble fiber. Two additional 3% OFSP diets contained 6% fat and 3 or 9% white-fleshed sweet potato (WFSP) powder with soluble fiber contents of 0.42 and 0.80%, respectively. Control, VA-, and betaC-supplemented groups were included. Simulated digestion experiments compared the bioaccessibility of betaC from boiled vs. oil stir-fried OFSP. All OFSP diets maintained VA status and 12% fat and WFSP-added diets improved VA status above baseline (P < 0.05). Bioefficacy, as bioconversion factors, in gerbils fed 12% fat (3.5 +/- 1.4 microg betaC:1 microg VA) was improved over the 3% fat and betaC groups (6.5 +/- 3.7 and 6.7 +/- 3.7 microg betaC:1 microg VA, respectively) (P < 0.05) but did not differ from WFSP-added groups or the 6% fat group with no WFSP. Stir-frying doubled the efficiency of betaC incorporation into micelles during small intestinal digestion in support of the stimulatory effect of dietary fat on bioefficacy in vivo. Soluble fiber intake derived from WFSP did not influence bioefficacy. Replacing WFSP with OFSP will affect VA status if adopted by target groups.

Micronutrients and anaemia.

Micronutrient deficiencies and anaemia remain as major health concerns for children in Bangladesh. Among the micronutrient interventions, supplementation with vitamin A to children aged less than five years has been the most successful, especially after distribution of vitamin A was combined with National Immunization Days. Although salt sold in Bangladesh is intended to contain iodine, much of the salt does not contain iodine, and iodine deficiency continues to be common. Anaemia similarly is common among all population groups and has shown no sign of improvement even when iron-supplementation programmes have been attempted. It appears that many other causes contribute to anaemia in addition to iron deficiency. Zinc deficiency is a key micronutrient deficiency and is covered in a separate paper because of its importance among new child-health interventions.

Detection of endotoxin in sera from children hospitalized for treatment of diarrhea in Bangladesh.

The level of circulating endotoxin was determined in the sera from children hospitalized for treatment of diarrhea at the International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh. A significant level of endotoxin was detected in the sera from 23 (54%) of 42 children. On the other hand, in 32 normal controls, endotoxin was below the limits of detection of the assay. Antibiotic and fluid therapy markedly reduced the level of serum endotoxin and improved the general condition of most patients. Non-survivors (n = 5) had higher levels of circulating endotoxin before treatment than survivors (n = 37), suggesting a significant correlation between the serum endotoxin level before treatment and mortality. Malnutrition did not affect the serum endotoxin level in the patients with diarrhea. It was suggested that infection of Gram-negative bacteria might be involved in a significant number of patients with diarrhea in Bangladesh and that endotoxin might play a pathogenic role in those patients.

Daily consumption of Indian spinach (Basella alba) or sweet potatoes has a positive effect on total-body vitamin A stores in Bangladeshi men.

BACKGROUND: Recent evidence suggests that the vitamin A equivalency of beta-carotene from plant sources is lower than previously estimated. OBJECTIVE: We assessed the effect of 60 d of daily supplementation with 750 microg retinol equivalents (RE) of either cooked, puréed sweet potatoes; cooked, puréed Indian spinach (Basella alba); or synthetic sources of vitamin A or beta-carotene on total-body vitamin A stores in Bangladeshi men. DESIGN: Total-body vitamin A stores in Bangladeshi men (n = 14/group) were estimated by using the deuterated-retinol-dilution technique before and after 60 d of supplementation with either 0 microg RE/d (white vegetables) or 750 microg RE/d as sweet potatoes, Indian spinach, retinyl palmitate, or beta-carotene (RE = 1 microg retinol or 6 microg beta-carotene) in addition to a low-vitamin A diet providing approximately 200 microg RE/d. Mean changes in vitamin A stores in the vegetable and beta-carotene groups were compared with the mean change in the retinyl palmitate group to estimate the relative equivalency of these vitamin A sources. RESULTS: Overall geometric mean (+/-SD) initial vitamin A stores were 0.108 +/- 0.067 mmol. Relative to the low-vitamin A control group, the estimated mean changes in vitamin A stores were 0.029 mmol for sweet potato (P = 0.21), 0.041 mmol for Indian spinach (P = 0.033), 0.065 mmol for retinyl palmitate (P < 0.001), and 0.062 mmol for beta-carotene (P < 0.002). Vitamin A equivalency factors (beta-carotene:retinol, wt:wt) were estimated as approximately 13:1 for sweet potato, approximately 10:1 for Indian spinach, and approximately 6:1 for synthetic beta-carotene. CONCLUSION: Daily consumption of cooked, puréed green leafy vegetables or sweet potatoes has a positive effect on vitamin A stores in populations at risk of vitamin A deficiency.