Abstract
Vitamin A deficiency is a major health risk for infants and children in low- and middle-income countries. This scoping review identified, quantified, and mapped research for use in updating nutrient requirements and upper limits for vitamin A in children aged 0 to 48 months, using health-based or modelling-based approaches. Structured searches were run on Medline, EMBASE, and Cochrane Central, from inception to 19 March 2021. Titles and abstracts were assessed independently in duplicate, as were 20% of full texts. Included studies were tabulated by question, methodology and date, with the most relevant data extracted and assessed for risk of bias. We found that the most recent health-based systematic reviews and trials assessed the effects of supplementation, though some addressed the effects of staple food fortification, complementary foods, biofortified maize or cassava, and fortified drinks, on health outcomes. Recent isotopic tracer studies and modelling approaches may help quantify the effects of bio-fortification, fortification, and food-based approaches for increasing vitamin A depots. A systematic review and several trials identified adverse events associated with higher vitamin A intakes, which should be useful for setting upper limits. We have generated and provide a database of relevant research. Full systematic reviews, based on this scoping review, are needed to answer specific questions to set vitamin A requirements and upper limits.
Highlights
Vitamin A deficiency is a major health problem for many children in low- and middleincome countries
Two main changes have occurred since submission: 1. Revision to search systematically for and include children aged 0 to 48 months, and include any relevant studies identified in infants and children aged up to 10 years, so that relevant studies, that may be scaled for younger children, could be included (WHO originally requested inclusion of studies on children aged 0 to 36 months)
The remaining 5201 papers underwent full-text assessment, but full texts could not be obtained for 775, of which 278 were potentially relevant studies of vitamin A
Summary
Vitamin A deficiency is a major health problem for many children in low- and middleincome countries. While vitamin A deficiency prevalence has fallen from 39% of children aged 6 to 59 months in low- and middle-income countries in 1991 to 29% in 2013, prevalence remains high in sub-Saharan Africa (48%) and South Asia (44%) [1]. A recent Cochrane systematic review [3] found that in populations at increased risk of deficiency, oral vitamin A supplementation (using doses of 50,000 to 200,000 IU) in children aged 6 months to 5 years reduced all-cause mortality (RR 0.88, 95% CI 0.83 to 0.93; 1,202,382 participants; high-quality evidence), mortality due to diarrhoea (RR 0.88, 95% CI 0.79 to 0.98; 1,098,538 participants; high-quality evidence), risk of diarrhoea (RR 0.85, 95% CI 0.82 to 0.87; 15 studies; 77,946 participants; low-quality evidence) and risk of measles (RR 0.50, 95% CI 0.37 to 0.67; 6 studies; 19,566 participants; moderate-quality evidence). Infant mortality was not reduced with neonatal supplementation in trials conducted in Africa (RR 1.07; 95% CI 1.00 to 1.15) [4], and a further review reiterated that neonatal vitamin A supplementation did not reduce all-cause mortality [5]
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