Biomarkers of Nutrition for Development (BOND)-Vitamin A Review

The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-informed advice to anyone with an interest in the role of nutrition in health. The BOND program provides information with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect, which will be especially useful for readers who want to assess nutrient status. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutritional status at the individual and population levels. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, folate, zinc, iron, vitamin A, and vitamin B-12. This review of vitamin A is the current article in this series. Although the vitamin was discovered >100 y ago, vitamin A status assessment is not trivial. Serum retinol concentrations are under homeostatic control due in part to vitamin A's use in the body for growth and cellular differentiation and because of its toxic properties at high concentrations. Furthermore, serum retinol concentrations are depressed during infection and inflammation because retinol-binding protein (RBP) is a negative acute-phase reactant, which makes status assessment challenging. Thus, this review describes the clinical and functional indicators related to eye health and biochemical biomarkers of vitamin A status (i.e., serum retinol, RBP, breast-milk retinol, dose-response tests, isotope dilution methodology, and serum retinyl esters). These biomarkers are then related to liver vitamin A concentrations, which are usually considered the gold standard for vitamin A status. With regard to biomarkers, future research questions and gaps in our current understanding as well as limitations of the methods are described.

Beta-carotene-rich orange-fleshed sweet potato improves the vitamin A status of primary school children assessed with the modified-relative-dose-response test

BACKGROUND

Beta-carotene-rich orange-fleshed sweet potato (OFSP) is an excellent source of provitamin A. In many developing countries, sweet potato is a secondary staple food and may play a role in controlling vitamin A deficiency.

OBJECTIVE

The objective was to determine the efficacy of daily consumption of boiled and mashed OFSP in improving the vitamin A status of primary school children.

DESIGN

Children aged 5-10 y were randomly assigned to 2 groups. The treatment group (n = 90) consumed 125 g boiled and mashed OFSP (1031 retinol activity equivalents/d as beta-carotene), and the control group (n = 90) consumed an equal amount of white-fleshed sweet potato devoid of beta-carotene for 53 school days. All children were dewormed to exclude helminthic infection. The modified-relative-dose-response test for vitamin A status was conducted before and after intervention.

RESULTS

The estimated intervention effect for the ratio of 3,4-didehydroretinol to retinol (DR:R) was -0.008 (95% CI: -0.015, -0.001; P = 0.0203), which indicated a greater improvement in vitamin A liver stores in the treatment group than in the control group. The proportions of children with normal vitamin A status (DR:R < 0.060) in the treatment group tended to increase from 78% to 87% (P = 0.096) and did not change significantly (from 86% to 82%) in the control group (P = 0.267). These proportions were not used to test the intervention effect or within-group changes because the study was powered to test the intervention effect on DR:R.

CONCLUSIONS

Consumption of OFSP improves vitamin A status and can play a significant role in developing countries as a viable long-term food-based strategy for controlling vitamin A deficiency in children.

Increased mortality in children with mild vitamin A deficiency

An average of 3481 preschool-age rural Indonesian children were re-examined every 3 months for 18 months. The mortality rate among children with mild xerophthalmia (night blindness and/or Bitot's spots) was on average 4 times the rate, and in some age groups 8 to 12 times the rate, among children without xerophthalmia. Mortality increased, almost linearly, with the severity of mild xerophthalmia (night blindness, Bitot's spots, and the two combined). These relations persisted after stratification for respiratory disease, wasting, gastroenteritis, pedal oedema, and childhood exanthems. Mild vitamin A deficiency was directly associated with at least 16% of all deaths in children aged from 1 to 6 years. These results suggest that mild xerophthalmia justifies vigorous community-wide intervention, as much to reduce childhood mortality as to prevent blindness, and that night blindness and Bitot's spots are as important as anthropometric indices in screening children to determine which of them need medical and nutritional attention.

Vitamin A supplements for preventing mortality, illness, and blindness in children aged under 5: systematic review and meta-analysis

OBJECTIVE

To determine if vitamin A supplementation is associated with reductions in mortality and morbidity in children aged 6 months to 5 years.

DESIGN

Systematic review and meta-analysis. Two reviewers independently assessed studies for inclusion. Data were double extracted; discrepancies were resolved by discussion. Meta-analyses were performed for mortality, illness, vision, and side effects.

DATA SOURCES

Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, Medline, Embase, Global Health, Latin American and Caribbean Health Sciences, metaRegister of Controlled Trials, and African Index Medicus. Databases were searched to April 2010 without restriction by language or publication status.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised trials of synthetic oral vitamin A supplements in children aged 6 months to 5 years. Studies of children with current illness (such as diarrhoea, measles, and HIV), studies of children in hospital, and studies of food fortification or β carotene were excluded.

RESULTS

43 trials with about 215,633 children were included. Seventeen trials including 194,483 participants reported a 24% reduction in all cause mortality (rate ratio=0.76, 95% confidence interval 0.69 to 0.83). Seven trials reported a 28% reduction in mortality associated with diarrhoea (0.72, 0.57 to 0.91). Vitamin A supplementation was associated with a reduced incidence of diarrhoea (0.85, 0.82 to 0.87) and measles (0.50, 0.37 to 0.67) and a reduced prevalence of vision problems, including night blindness (0.32, 0.21 to 0.50) and xerophthalmia (0.31, 0.22 to 0.45). Three trials reported an increased risk of vomiting within the first 48 hours of supplementation (2.75, 1.81 to 4.19).

CONCLUSIONS

Vitamin A supplementation is associated with large reductions in mortality, morbidity, and vision problems in a range of settings, and these results cannot be explained by bias. Further placebo controlled trials of vitamin A supplementation in children between 6 and 59 months of age are not required. However, there is a need for further studies comparing different doses and delivery mechanisms (for example, fortification). Until other sources are available, vitamin A supplements should be given to all children at risk of deficiency, particularly in low and middle income countries.

Maternal vitamin A supplementation and lung function in offspring

BACKGROUND

Vitamin A is important in regulating early lung development and alveolar formation. Maternal vitamin A status may be an important determinant of embryonic alveolar formation, and vitamin A deficiency in a mother during pregnancy could have lasting adverse effects on the lung health of her offspring. We tested this hypothesis by examining the long-term effects of supplementation with vitamin A or beta carotene in women before, during, and after pregnancy on the lung function of their offspring, in a population with chronic vitamin A deficiency.

METHODS

We examined a cohort of rural Nepali children 9 to 13 years of age whose mothers had participated in a placebo-controlled, double-blind, cluster-randomized trial of vitamin A or beta-carotene supplementation between 1994 and 1997.

RESULTS

Of 1894 children who were alive at the end of the original trial, 1658 (88%) were eligible to participate in the follow-up trial. We performed spirometry in 1371 of the children (83% of those eligible) between October 2006 and March 2008. Children whose mothers had received vitamin A had a forced expiratory volume in 1 second (FEV(1)) and a forced vital capacity (FVC) that were significantly higher than those of children whose mothers had received placebo (FEV(1), 46 ml higher with vitamin A; 95% confidence interval [CI], 6 to 86; FVC, 46 ml higher with vitamin A; 95% CI, 8 to 84), after adjustment for height, age, sex, body-mass index, calendar month, caste, and individual spirometer used. Children whose mothers had received beta carotene had adjusted FEV(1) and FVC values that were similar to those of children whose mothers had received placebo (FEV(1), 14 ml higher with beta carotene; 95% CI, -24 to 54; FVC, 17 ml higher with beta carotene, 95% CI, -21 to 55).

CONCLUSIONS

In a chronically undernourished population, maternal repletion with vitamin A at recommended dietary levels before, during, and after pregnancy improved lung function in offspring. This public health benefit was apparent in the preadolescent years.

Vitamin A Supplementation Programs and Country-Level Evidence of Vitamin A Deficiency

Vitamin A supplementation (VAS) programs targeted at children aged 6–59 months are implemented in many countries. By improving immune function, vitamin A (VA) reduces mortality associated with measles, diarrhea, and other illnesses. There is currently a debate regarding the relevance of VAS, but amidst the debate, researchers acknowledge that the majority of nationally-representative data on VA status is outdated. To address this data gap and contribute to the debate, we examined data from 82 countries implementing VAS programs, identified other VA programs, and assessed the recentness of national VA deficiency (VAD) data. We found that two-thirds of the countries explored either have no VAD data or data that were >10 years old (i.e., measured before 2006), which included twenty countries with VAS coverage ≥70%. Fifty-one VAS programs were implemented in parallel with at least one other VA intervention, and of these, 27 countries either had no VAD data or data collected in 2005 or earlier. To fill these gaps in VAD data, countries implementing VAS and other VA interventions should measure VA status in children at least every 10 years. At the same time, the coverage of VA interventions can also be measured. We identified three countries that have scaled down VAS, but given the lack of VA deficiency data, this would be a premature undertaking in most countries without appropriate status assessment. While the global debate about VAS is important, more attention should be directed towards individual countries where programmatic decisions are made.

Retinol-induced stage synchronization in seminiferous tubules of the rat

Vitamin A deficiency (VAD) in rats causes a progressive germ cell depletion and cessation of spermatogenesis resulting in seminiferous tubules which contain only Sertoli cells, spermatogonia and a small number of preleptotene spermatocytes. Spermatogenesis can be rapidly restored by the administration of retinol. Our preliminary studies suggested a partial stage synchronization of many seminiferous tubules in VAD male rats subsequently treated with retinol. To confirm this observation and to achieve a better synchronization, VAD rats received 2 SC injections of retinol suspended in sesame oil followed by daily oral administrations of 0.5 mg of retinol. In all rats an almost perfect synchronous stage development of seminiferous tubules evolved in a predictable manner and was maintained through 2 spermiations.

Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age

BACKGROUND

Vitamin A deficiency (VAD) is a major public health problem in low- and middle-income countries, affecting 190 million children under five years of age and leading to many adverse health consequences, including death. Based on prior evidence and a previous version of this review, the World Health Organization has continued to recommend vitamin A supplementation for children aged 6 to 59 months. There are new data available from recently published randomised trials since the previous publication of this review in 2010, and this update incorporates this information and reviews the evidence.

OBJECTIVES

To assess the effects of vitamin A supplementation (VAS) for preventing morbidity and mortality in children aged six months to five years.

SEARCH METHODS

In March 2016 we searched CENTRAL, Ovid MEDLINE, Embase, six other databases, and two trials registers. We also checked reference lists and contacted relevant organisations and researchers to identify additional studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and cluster-RCTs evaluating the effect of synthetic VAS in children aged six months to five years living in the community. We excluded studies involving children in hospital and children with disease or infection. We also excluded studies evaluating the effects of food fortification, consumption of vitamin A rich foods, or beta-carotene supplementation.

DATA COLLECTION AND ANALYSIS

For this update, two reviewers independently assessed studies for inclusion and abstracted data, resolving discrepancies by discussion. We performed meta-analyses for outcomes, including all-cause and cause-specific mortality, disease, vision, and side effects. We used the GRADE approach to assess the quality of the evidence.

MAIN RESULTS

We identified 47 studies (4 of which are new to this review), involving approximately 1,223,856 children. Studies took place in 19 countries: 30 (63%) in Asia, 16 of these in India; 8 (17%) in Africa; 7 (15%) in Latin America, and 2 (4%) in Australia. About one-third of the studies were in urban/periurban settings, and half were in rural settings; the remaining studies did not clearly report settings. Most of the studies included equal numbers of girls and boys and lasted about a year. The included studies were at variable overall risk of bias; however, evidence for the primary outcome was at low risk of bias. A meta-analysis for all-cause mortality included 19 trials (1,202,382 children). At longest follow-up, there was a 12% observed reduction in the risk of all-cause mortality for vitamin A compared with control using a fixed-effect model (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.83 to 0.93; high-quality evidence). This result was sensitive to choice of model, and a random-effects meta-analysis showed a different summary estimate (24% reduction: RR 0.76, 95% CI 0.66 to 0.88); however, the confidence intervals overlapped with that of the fixed-effect model. Nine trials reported mortality due to diarrhoea and showed a 12% overall reduction for VAS (RR 0.88, 95% CI 0.79 to 0.98; 1,098,538 participants; high-quality evidence). There was no significant effect for VAS on mortality due to measles, respiratory disease, and meningitis. VAS reduced incidence of diarrhoea (RR 0.85, 95% CI 0.82 to 0.87; 15 studies; 77,946 participants; low-quality evidence) and measles (RR 0.50, 95% CI 0.37 to 0.67; 6 studies; 19,566 participants; moderate-quality evidence). However, there was no significant effect on incidence of respiratory disease or hospitalisations due to diarrhoea or pneumonia. There was an increased risk of vomiting within the first 48 hours of VAS (RR 1.97, 95% CI 1.44 to 2.69; 4 studies; 10,541 participants; moderate-quality evidence).

AUTHORS' CONCLUSIONS

Vitamin A supplementation is associated with a clinically meaningful reduction in morbidity and mortality in children. Therefore, we suggest maintaining the policy of universal supplementation for children under five years of age in populations at risk of VAD. Further placebo-controlled trials of VAS in children between six months and five years of age would not change the conclusions of this review, although studies that compare different doses and delivery mechanisms are needed. In populations with documented vitamin A deficiency, it would be unethical to conduct placebo-controlled trials.

Effect of massive dose vitamin A on morbidity and mortality in Indian children

The effect of vitamin A supplementation on preschool child morbidity and mortality was assessed in a prospective double-blind placebo-controlled study around Hyderabad, India. Every six months 200,000 IU vitamin A was given to 7691 children (treatment group) whereas 8084 children received a placebo (control group). Morbidity and mortality data were collected every three months. Risk of respiratory infection was higher in children with mild xerophthalmia than in children with normal eyes. Vitamin A supplementation had no effect on morbidity status. Mortality rates were similar in the two groups; it was highest in children who did not receive either vitamin A or placebo. The findings suggest that vitamin A supplementation alone may not reduce child mortality.

Disturbed Vitamin A Metabolism in Non-Alcoholic Fatty Liver Disease (NAFLD)

Vitamin A is required for important physiological processes, including embryogenesis, vision, cell proliferation and differentiation, immune regulation, and glucose and lipid metabolism. Many of vitamin A’s functions are executed through retinoic acids that activate transcriptional networks controlled by retinoic acid receptors (RARs) and retinoid X receptors (RXRs).The liver plays a central role in vitamin A metabolism: (1) it produces bile supporting efficient intestinal absorption of fat-soluble nutrients like vitamin A; (2) it produces retinol binding protein 4 (RBP4) that distributes vitamin A, as retinol, to peripheral tissues; and (3) it harbors the largest body supply of vitamin A, mostly as retinyl esters, in hepatic stellate cells (HSCs). In times of inadequate dietary intake, the liver maintains stable circulating retinol levels of approximately 2 μmol/L, sufficient to provide the body with this vitamin for months. Liver diseases, in particular those leading to fibrosis and cirrhosis, are associated with impaired vitamin A homeostasis and may lead to vitamin A deficiency. Liver injury triggers HSCs to transdifferentiate to myofibroblasts that produce excessive amounts of extracellular matrix, leading to fibrosis. HSCs lose the retinyl ester stores in this process, ultimately leading to vitamin A deficiency. Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and is a spectrum of conditions ranging from benign hepatic steatosis to non-alcoholic steatohepatitis (NASH); it may progress to cirrhosis and liver cancer. NASH is projected to be the main cause of liver failure in the near future. Retinoic acids are key regulators of glucose and lipid metabolism in the liver and adipose tissue, but it is unknown whether impaired vitamin A homeostasis contributes to or suppresses the development of NAFLD. A genetic variant of patatin-like phospholipase domain-containing 3 (PNPLA3-I148M) is the most prominent heritable factor associated with NAFLD. Interestingly, PNPLA3 harbors retinyl ester hydrolase activity and PNPLA3-I148M is associated with low serum retinol level, but enhanced retinyl esters in the liver of NAFLD patients. Low circulating retinol in NAFLD may therefore not reflect true “vitamin A deficiency”, but rather disturbed vitamin A metabolism. Here, we summarize current knowledge about vitamin A metabolism in NAFLD and its putative role in the progression of liver disease, as well as the therapeutic potential of vitamin A metabolites.

Childhood mortality after a high dose of vitamin A in a high risk population

OBJECTIVES

To determine whether a single high dose of vitamin A given to all children in communities with high mortality and malnutrition could affect mortality and to assess whether periodic community wide supplementation could be readily incorporated into an ongoing primary health programme.

DESIGN

Opportunistic controlled trial.

SETTING

Jumla district, Nepal.

SUBJECTS

All children aged under 5 years; 3786 in eight subdistricts given single dose of vitamin A and 3411 in remaining eight subdistricts given no supplementation.

MAIN OUTCOME MEASURES

Mortality and cause of death in the five months after supplementation.

RESULTS

Risk of death for children aged 1-59 months in supplemented communities was 26% lower (relative risk 0.74, 95% confidence interval 0.55 to 0.99) than in unsupplemented communities. The reduction in mortality was greatest among children aged 6-11 months: death rate (deaths/1000 child years at risk) was 133.8 in supplemented children and 260.8 in unsupplemented children (relative risk 0.51, 0.30 to 0.89). The death rate from diarrhoea was also reduced (63.5 supplemented v 97.5 unsupplemented; relative risk 0.65, 0.44 to 0.95). The extra cost per death averted was about $11.

CONCLUSION

The results support a role for Vitamin A in increasing child survival. The supplementation programme was readily integrated with the ongoing community health programme at little extra cost.

Night blindness during pregnancy and subsequent mortality among women in Nepal: effects of vitamin A and beta-carotene supplementation

Night blindness due to vitamin A deficiency is common during pregnancy among women in Nepal. The authors assessed the risk of maternal death during and after a pregnancy with night blindness among women participating in a cluster-randomized, placebo-controlled vitamin A and beta-carotene supplementation trial in Nepal from July 1994 to September 1997. Subjects were 877 women with night blindness and 9,545 women without night blindness during pregnancy. Women were followed from the time they declared that they were pregnant through the end of the study, representing a median follow-up of 90 weeks (interquartile range: 64-121 weeks). Mortality of night-blind women in the placebo group was 3,601 per 100,000 pregnancies. In comparison, the relative risk of dying among nonnight-blind women in the placebo group was 0.26 (95% confidence interval (CI): 0.13, 0.55), and the relative risk among women with or without night blindness in the vitamin A/beta-carotene group was 0.32 (95% CI: 0.10, 0.91) and 0.18 (95% CI: 0.09, 0.36), respectively. Night-blind women were five times (95% CI: 2.20, 10.58) more likely to die from infections than were women who were not night blind. These findings show that night blindness during pregnancy is a risk factor of both short- and long-term mortality among women. Vitamin A/beta-carotene supplementation ameliorates this risk to a large extent.

Hematopoietic studies in vitamin A deficiency

Recent studies of experimental vitamin A deficiency in man led the authors to conclude that anemia may result from lack of vitamin A. A review of numerous nutrition surveys in underdeveloped countries enhanced the suspicion that deficiency of vitamin A does contribute to the prevalence of anemia. Preliminary studies of vitamin A-deficient rats confirmed previous observations that anemia may result from lack of this vitamin. The livers of these animals had very low concentrations of vitamin A but normal or increased concentrations of iron. The finding of anemia is in contrast with other reports that vitamin A deficiency may cause elevated values for hemoglobin and hematocrit. The authors suggest that loss of taste and smell as a result of deficiency may account for refusal of experimental animals to eat and drink enough to prevent inanitation and dehydration. The resulting hemoconcentration may mask the true hematological picture, which is one of anemia.

Consequences of revised estimates of carotenoid bioefficacy for dietary control of vitamin A deficiency in developing countries

According to existing recommendations of the Food and Agriculture Organization (FAO)/World Health Organization (WHO), the amount of provitamin A in a mixed diet having the same vitamin A activity as 1 microg of retinol is 6 microg of beta-carotene or 12 microg of other provitamin A carotenoids. The efficiency of this conversion is referred to as bioefficacy. Recently, using data from healthy people in developed countries and based on a two-step process, the U.S. Institute of Medicine (IOM) derived new conversion factors. The first step established the bioefficacy of beta-carotene in oil at 2 microg having the same vitamin A activity as 1 microg of retinol; the second step established the bioavailability of beta-carotene in foods relative to that of beta-carotene in oil at 1:6. Thus, 2 microg of beta-carotene in oil or 12 microg of beta-carotene in mixed foods has the same vitamin A activity as 1 microg of retinol. Based on existing FAO food balance sheets and the FAO/WHO conversion rates, all populations should be able to meet their vitamin A requirements from existing dietary sources. However, using the new IOM conversion rates, populations in developing countries could not achieve adequacy. Additionally, field studies suggest that, instead of 12 microg, 21 microg of beta-carotene has the same vitamin A activity as 1 microg of retinol, which implies that effective vitamin A intake is even lower. Therefore, controlling vitamin A deficiency in developing countries requires not only vitamin A supplementation but also food-based approaches, including food fortification, and possibly the introduction of new strains of plants with enhanced vitamin A activity.

Abnormal T-cell subset proportions in vitamin-A-deficient children

Although vitamin A deficiency in children seems to increase susceptibility to infection and community trials have shown that vitamin A supplementation can reduce childhood mortality from infectious diseases, the underlying biological mechanisms are largely unknown. We conducted a randomised, double-masked, placebo-controlled clinical trial among children in West Java, Indonesia, to determine whether vitamin A deficiency is associated with abnormalities in T-cell subsets and whether vitamin A supplementation affects T-cell subsets. We studied 55 children aged 3-6 years--30 with xerophthalmia and 25 without. Acutely malnourished children (< 80% of reference weight-for-height) were excluded. CD4/CD8 ratios and the proportions of circulating CD4 naive, CD4 memory, CD8, CD45RA, and CD8, CD45RO T-cell subsets were measured. Children with xerophthalmia had lower CD4/CD8 ratios (p < 0.08), lower proportions of CD4 naive T cells (p < 0.03), and higher proportions of CD8, CD45RO T cells (p < 0.04) than those without xerophthalmia. 26 children were given vitamin A supplementation (60 mg retinol equivalent) and 29 received placebo. 5 weeks later the vitamin A group had higher CD4/CD8 ratios (p < 0.001), higher proportions of CD4 naive T cells (p < 0.01), and lower proportions of CD8, CD45RO T cells (p < 0.05) than the placebo group. Vitamin-A-deficient children have underlying immune abnormalities in T-cell subsets and these abnormalities are reversible with vitamin A supplementation.

Vitamin A supplementation in children with poor vitamin A and iron status increases erythropoietin and hemoglobin concentrations without changing total body iron

BACKGROUND

Vitamin A deficiency impairs iron metabolism; vitamin A supplementation of vitamin A-deficient populations may reduce anemia. The mechanism of these effects is unclear. In vitro and in animal models, vitamin A treatment increases the production of erythropoietin (EPO), a stimulant of erythropoiesis.

OBJECTIVE

We measured the effect of vitamin A supplementation on hemoglobin, iron status, and circulating EPO concentrations in children with poor iron and vitamin A status.

DESIGN

In a double-blind, randomized trial, Moroccan schoolchildren (n = 81) were given either vitamin A (200,000 IU) or placebo at baseline and at 5 mo. At baseline, 5 mo, and 10 mo, hemoglobin, indicators of iron and vitamin A status, and EPO were measured.

RESULTS

At baseline, 54% of children were anemic; 77% had low vitamin A status. In the vitamin A group at 10 mo, serum retinol improved significantly compared with the control group (P < 0.02). Vitamin A treatment increased mean hemoglobin by 7 g/L (P < 0.02) and reduced the prevalence of anemia from 54% to 38% (P < 0.01). Vitamin A treatment increased mean corpuscular volume (P < 0.001) and decreased serum transferrin receptor (P < 0.001), indicating improved iron-deficient erythropoiesis. Vitamin A decreased serum ferritin (P < 0.02), suggesting mobilization of hepatic iron stores. Calculated from the ratio of transferrin receptor to serum ferritin, overall body iron stores remained unchanged. In the vitamin A group at 10 mo, we observed an increase in EPO (P < 0.05) and a decrease in the slope of the regression line of log10(EPO) on hemoglobin (P < 0.01).

CONCLUSION

In children deficient in vitamin A and iron, vitamin A supplementation mobilizes iron from existing stores to support increased erythropoiesis, an effect likely mediated by increases in circulating EPO.

Randomised trial of effect of vitamin A supplementation on antibody response to measles vaccine in Guinea-Bissau, west Africa

BACKGROUND

WHO has recommended vitamin A supplementation for children aged 6 months or older in developing countries at the same time as immunisation. One study has reported significantly lower seroconversion ratios among children who have received vitamin A supplements with measles vaccine at age 6 months. The aim of our study was to assess the effect of vitamin A supplementation on antibody response to measles vaccination at age 9 months, which is the more common age for immunisation in developing countries.

METHODS

In an urban community in Guinea-Bissau, we did a randomised, double-blind, placebo-controlled study of the effect of simultaneous vaccination and vitamin A supplementation in 462 children who received either a two-dose schedule of measles vaccine at the ages of 6 months and 9 months (150 infants) or one dose of measles vaccine at age 9 months (312 infants). Children were followed up to the age of 18 months and a blood sample was then collected to assess the antibody response.

FINDINGS

397 (86%) of the children took part in the follow-up (52 [11%] had moved and 13 [3%] had died). Among children who received a two-dose vaccine schedule, seroconversion was 98%. There was no difference in seroconversion or geometric mean titre (GMT) for children receiving vitamin A compared with children receiving no supplement. Among children receiving only one dose of measles vaccine at age 9 months, seroconversion was 95%. The GMT was significantly higher in children receiving vitamin A than in those receiving no supplement (3704 vs 2439 mIU; GMT ratio 1.52 [1.22-1.88]). The effect on plasma antibody concentration in the blood was stronger for boys (3902 vs 1916 mIU; GMT ratio 2.04 [1.53-2.72]) than for girls (3502 vs 3017 mIU; GMT ratio 1.16 [0.85-1.58]) who had received vitamin A with measles vaccine. In a multivariate analysis of variance adjusted for sex, vitamin A supplementation was associated with higher antibody titres (p < 0.001). There was a significant interaction between vitamin A supplementation and sex (p = 0.02).

INTERPRETATION

There is no indication that simultaneous administration of measles vaccine and vitamin A supplements has a negative effect on measles immunity. Among the children who had received two doses of measles vaccine at the ages of 6 months and 9 months, supplements of vitamin A had no significant effect. Among children only receiving one dose of measles vaccine at age 9 months, 100,000 IU vitamin A increased antibody concentrations, especially for boys.

Effects of vitamin A or beta carotene supplementation on pregnancy-related mortality and infant mortality in rural Bangladesh: a cluster randomized trial

CONTEXT

Maternal vitamin A deficiency is a public health concern in the developing world. Its prevention may improve maternal and infant survival.

OBJECTIVE

To assess efficacy of maternal vitamin A or beta carotene supplementation in reducing pregnancy-related and infant mortality.

DESIGN, SETTING, AND PARTICIPANTS

Cluster randomized, double-masked, placebo-controlled trial among pregnant women 13 to 45 years of age and their live-born infants to 12 weeks (84 days) postpartum in rural northern Bangladesh between 2001 and 2007. Interventions Five hundred ninety-six community clusters (study sectors) were randomized for pregnant women to receive weekly, from the first trimester through 12 weeks postpartum, 7000 μg of retinol equivalents as retinyl palmitate, 42 mg of all-trans beta carotene, or placebo. Married women (n = 125,257) underwent 5-week surveillance for pregnancy, ascertained by a history of amenorrhea and confirmed by urine test. Blood samples were obtained from participants in 32 sectors (5%) for biochemical studies.

MAIN OUTCOME MEASURES

All-cause mortality of women related to pregnancy, stillbirth, and infant mortality to 12 weeks (84 days) following pregnancy outcome.

RESULTS

Groups were comparable across risk factors. For the mortality outcomes, neither of the supplement group outcomes was significantly different from the placebo group outcomes. The numbers of deaths and all-cause, pregnancy-related mortality rates (per 100,000 pregnancies) were 41 and 206 (95% confidence interval [CI], 140-273) in the placebo group, 47 and 237 (95% CI, 166-309) in the vitamin A group, and 50 and 250 (95% CI, 177-323) in the beta carotene group. Relative risks for mortality in the vitamin A and beta carotene groups were 1.15 (95% CI, 0.75-1.76) and 1.21 (95% CI, 0.81-1.81), respectively. In the placebo, vitamin A, and beta carotene groups the rates of stillbirth and infant mortality were 47.9 (95% CI, 44.3-51.5), 45.6 (95% CI, 42.1-49.2), and 51.8 (95% CI, 48.0-55.6) per 1000 births and 68.1 (95% CI, 63.7-72.5), 65.0 (95% CI, 60.7-69.4), and 69.8 (95% CI, 65.4-72.3) per 1000 live births, respectively. Vitamin A compared with either placebo or beta carotene supplementation increased plasma retinol concentrations by end of study (1.46 [95% CI, 1.42-1.50] μmol/L vs 1.13 [95% CI, 1.09-1.17] μmol/L and 1.18 [95% CI, 1.14-1.22] μmol/L, respectively; P < .001) and reduced, but did not eliminate, gestational night blindness (7.1% for vitamin A vs 9.2% for placebo and 8.9% for beta carotene [P < .001 for both]).

CONCLUSION

Use of weekly vitamin A or beta carotene in pregnant women in Bangladesh, compared with placebo, did not reduce all-cause maternal, fetal, or infant mortality.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00198822.

Iron metabolism and vitamin A deficiency in children in northeast Thailand

To investigate the association between vitamin A and iron metabolism, two studies were carried out: a cross-sectional study and an intervention trial. The cross-sectional analysis was carried out in 1060 children aged 1-8 y. Multiple-regression analysis was used to adjust for effects of age, gender, indices of the protein nutritional status, and infections. Retinol was significantly associated with hematocrit, serum Fe, transferrin, ferritin, and saturation of transferrin (%ST). To obtain further evidence as to whether this observed association is a causal one, an intervention trial was carried out. After collection of the baseline data of 300 children, 166 children with a hemoglobin concentration less than 7.5 mmol/L were selected. A random sub-sample of 78 children received vitamin A capsules; the other children served as control subjects. Two months after supplementation significant differences, adjusted for age, were found for retinol, retinol-binding protein, serum Fe, and %ST between the supplemented and the control group. After 4 mo none of the indices were found to be significantly different between the supplemented and the control group. Periodic massive doses of vitamin A may play a role in improving the Fe status as well.

Vitamin A supplementation for preventing morbidity and mortality in children from 6 months to 5 years of age

BACKGROUND

Vitamin A deficiency (VAD) is a major public health problem in low and middle income countries affecting 190 million children under 5. VAD can lead to many adverse health consequences, including death.

OBJECTIVES

To evaluate the effect of vitamin A supplementation (VAS) for preventing morbidity and mortality in children aged 6 months to 5 years.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2010 Issue 2),  MEDLINE (1950 to April Week 2 2010), EMBASE (1980 to 2010 Week 16), Global Health (1973 to March 2010), Latin American and Caribbean Health Sciences (LILACS), metaRegister of Controlled Trials and African Index Medicus (27 April 2010).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and cluster RCTs evaluating the effect of synthetic VAS in children aged 6 months to 5 years living in the community. We excluded studies concerned with children in hospital and children with disease or infection. We excluded studies evaluating the effects of food fortification, consumption of vitamin A rich foods or beta-carotene supplementation.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion. Data were double abstracted and discrepancies were resolved by discussion. Meta-analyses were performed for outcomes including all-cause and cause-specific mortality, disease, vision, and side-effects.

MAIN RESULTS

43 trials involving 215,633 children were included. A meta-analysis for all-cause mortality included 17 trials comprising 194,795 children with 3536 deaths in both groups. At follow-up, there was a 24% observed reduction in the risk of all-cause mortality for Vitamin A compared with Control (Relative risk (RR) = 0.76 [95% confidence interval (CI) 0.69, 0.83]). Seven trials reported diarrhoea mortality and a 28% overall reduction for VAS (RR = 0.72 [0.57, 0.91]). There was no significant effect of VAS on cause specific mortality of measles, respiratory disease and meningitis. VAS reduced incidence of diarrhoea (RR = 0.85 [0.82, 0.87]) and measles morbidity (RR = 0.50 [0.37, 0.67]); however, there was no significant effect on incidence of respiratory disease or hospitalisations due to diarrhoea or pneumonia. There was an increased risk of vomiting within the first 48 hours of VAS (RR = 2.75 [1.81, 4.19]).

AUTHORS' CONCLUSIONS

VAS is effective in reducing all-cause mortality by about 24% compared to no treatment. In our opinion, given the evidence that VAS causes considerable reduction in child mortality, further placebo-controlled trials of VAS in children between 6 months and 5 years of age are not required. There is a need for further studies comparing different doses and delivery mechanisms (for example, fortification).

Effect of daily and weekly micronutrient supplementation on micronutrient deficiencies and growth in young Vietnamese children

BACKGROUND

Micronutrient deficiencies remain common in preschool children in developing countries. Interventions focus on single micronutrients and often lack effectiveness. Weekly instead of daily supplementation may improve effectiveness.

OBJECTIVE

The efficacy of weekly and daily supplementation in reducing anemia prevalence and in improving the zinc, vitamin A, and growth status of 6-24-mo-old Vietnamese children was investigated.

DESIGN

In this double-blind, placebo-controlled trial, the daily group (n = 55) received 8 mg elemental Fe (as iron sulfate), 5 mg elemental Zn (as zinc sulfate), 333 microg retinol, and 20 mg vitamin C 5 d/wk for 3 mo. The weekly group (n = 54) received 20 mg Fe, 17 mg Zn, 1700 microg retinol, and 20 mg vitamin C once a week. A third group (n = 54) received a placebo only. Venous blood samples were collected at the start and end of the supplementation period and anthropometric measurements were taken at the start and 3 mo after the end of supplementation.

RESULTS

At baseline, 45.6% of subjects had hemoglobin concentrations < 110 g/L, 36.3% had zinc concentrations < 10.71 micromol/L, and 45.6% had retinol concentrations <0.70 micromol/L. Hemoglobin, retinol, and zinc concentrations of both the weekly and daily groups increased similarly compared with the placebo group (P < 0.001). There was no significant difference in growth between the supplemented groups and the placebo group. However, the height-for-age of subjects stunted at baseline increased with z scores of 0.48 (P < 0.001) and 0.37 (P < 0.001) for the daily and weekly groups, respectively.

CONCLUSIONS

Weekly and daily supplementation improved hemoglobin, zinc, and retinol concentrations similarly. Neither intervention affected growth of the overall population, but growth of children stunted at baseline was improved through both types of supplementation.

Vitamin A supplementation fails to reduce incidence of acute respiratory illness and diarrhea in preschool-age Indonesian children

Vitamin A supplementation of populations of vitamin A-deficient preschool-age children has been shown to reduce childhood mortality, but the primary preventive effects of such supplements on childhood infectious diseases have not been carefully evaluated. We conducted an individually randomized, placebo-controlled, double-masked trial among 1,407 Indonesian preschool-age children, to measure the effects of high dose vitamin A on acute respiratory and diarrheal illnesses. Signs and symptoms of morbidity were monitored using every other day home surveillance by trained interviewers. High dose vitamin A supplements increased the incidence of acute respiratory illnesses (ARI) by 8%, and acute lower respiratory illnesses (ALRI) by 39%. These detrimental effects on acute lower respiratory illnesses were most marked in children with adequate nutritional status (rate ratio 1.83, 95% confidence interval 1.257-2.669). In contrast, vitamin A tended to be protective of ALRI in chronically malnourished children (rate ratio 0.71, 95% confidence interval 0.375-1.331). There was no overall effect of high-dose vitamin A supplements on the incidence of diarrheal disease (rate ratio 1.06, 95% confidence interval 0.920-1.225). However, we found a significant interaction between supplementation and age: vitamin A increased the incidence of diarrhea in children < 30 mo of age, but tended to reduce the incidence in older children. The finding of a significant adverse effect of vitamin A supplements in adequately nourished children highlights the need to review the criteria for selecting populations of preschool-age children for vitamin A supplementation.

The biological activity of retinoic acid in the domestic fowl and the effects of vitamin A deficiency on the chick embryo

1. Male and female chickens were reared from hatching on vitamin A-free diets, either unsupplemented or containing retinoic acid (vitamin A acid), methyl retinoate or retinyl acetate (vitamin A acetate). The birds given retinyl acetate grew well and had a normal appearance, but those given the unsupplemented diet died before 4 weeks of age after developing typical signs of avitaminosis A. The birds given retinoic acid or methyl retinoate did not show overt signs of vitamin A deficiency or other abnormalities except for a progressive failure of vision. Minimal histological changes were found in their retinas, and their vision was rapidly restored after feeding with retinyl acetate.

2. The cocks maintained with retinoic acid or methyl retinoate had normal testes and the hens laid eggs at a normal rate, but although their eggs could be obtained fertile the development of the embryo became abnormal after 2 days incubation and it always died. The development of the embryos could be stimulated and sometimes restored to normal by injection of various forms of vitamin A into the eggs before incubation, or by previous administration of retinyl acetate to the hens.

3. It is concluded that feeding retinoic acid as the sole source of vitamin A enables the hen to produce eggs that lack vitamin A but are otherwise normal, thus permitting the demonstration of a hitherto undescribed requirement of the early chick embryo for vitamin A.

4. The toxicity of vitamin A derivatives to chick embryos was investigated; injected retinoic acid was found to be extremely toxic.