Factors influencing micronutrient status in school children and role of indigenous vegetables for improving micronutrient intake in rural Tanzania
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Date
2022
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Sokoine University of Agriculture
Abstract
Introduction: Deficiencies of iron, zinc and vitamin A in the body continue to affect the
health and wellbeing of women and children in Tanzania; consequently, leading to retarded
growth during childhood and poor cognitive development, hence, reduced learning
capacity and poor school attendance. Moreover, micronutrient deficiencies lower
immunity; therefore, reduce ability of the body to fight infections, making children highly
susceptible to infections. Factors that contribute to micronutrient deficiencies include
inadequate consumption of diverse foods, high prevalence of infectious diseases and
inefficient utilization of micronutrients in the body due to persistent inflammations and
heavy parasitic infestations. This study aimed at determining the prevalence of
micronutrient deficiency and associated factors among school children living in rural
households of Kilosa and Chamwino districts in Tanzania. The study determined the
concentration of haemoglobin in the blood and status of micronutrients iron, zinc, vitamin
A, vitamin E and carotenoids in the serum. The anthropometric measurements of the
school children were also assessed to establish their nutritional status. Furthermore, the
nutrient intake of school children and the micronutrient composition of selected indigenous
leafy vegetables (ILVs) commonly consumed in study areas were also determined to
provide data to guide their consumption.
Methods: This study used a follow-up design in which two sequential cross sectional
surveys were conducted. The baseline survey was conducted in July-August 2016 to assess
the nutritional and micronutrient status of the school children prior to the implementation
of an integrated home gardening intervention which started in July 2017- May 2018. The
second or endline survey was conducted in July-August 2018 one year after the
implementation of an integrated home gardening intervention. The study population
included school children of age between five and ten years, who were enrolled to the study
together with their mothers or caregivers. The sample size at baseline was 666 child
mother or caregiver pairs obtained through a simple random sampling technique. The study
areas were purposively selected based on the Scale-N project criteria; this included
Dodoma region, where Chamwino district was selected and was represented by Mzula and
Chinoje villages; for Morogoro region, Kilosa district was selected and was represented by
Tindiga and Mhenda-Kitunduweta villages.
Data on socio-demographic variables such as age, gender and morbidity were collected
using a pretested questionnaire whereas for dietary intake a 24-hour recall method was
used. Anthropometric status was assessed using measurements of weight, height and mid
upper arm circumference (MUAC). Serum concentration of retinol (vitamin A),
carotenoids and tocopherols (vitamin E) were determined using the high-performance
liquid chromatography (HPLC) while iron status markers (ferritin, soluble transferrin
receptor), infection or inflammation markers (C-reactive protein, α-1 glycoprotein) by a
sandwich enzyme-linked immune-sorbent assay (ELISA) technique and serum zinc by a
spectrophotometric method. School children-mothers or caregivers pairs were followed for
two years to assess anthropometric, dietary and biochemical parameters (serum
micronutrients and infection markers). In the selected ILVs the concentration of provitamin
A carotenoids, tocopherols, and ascorbic acid (AA) were determined using HPLC; the
minerals iron, calcium, magnesium, zinc, and phosphorus were determined using
Inductively Coupled Plasma-Optical Emission Spectrophotometry (ICP-OES), while
phytic acid content was determined using a photometric method.
Results: At baseline the overall prevalence of stunting was 28.1%, underweight 14.4%,
and overweight was 5%. Micronutrient deficiencies showed varied prevalence; whereby
43% of the children had anaemia, 29.3% showed deficiency of iron (ID), 24.9 % were
vitamin A deficient (VAD), and 26.4% had zinc deficiency (ZnD). The overall prevalence
of reported malaria and diarrhoea was 30.7% and 20.7% respectively. Dietary intake data
indicated that, only small proportions of children reached the recommended daily
micronutrient intakes for zinc (4%), vitamin A (19%) and B vitamins (14–46%), except for
iron (74%). Stunting was highly associated (p <0.001) with underweight in both districts
and with VAD in Chamwino (p <0.05). Anaemia was mainly predicted by ID, VAD, and
ZnD in Chamwino while in Kilosa it was predicted by elevated infection markers, C -
reactive protein (CRP) and α-1 glycoprotein (AGP). Higher serum carotenoids indicative
of a diet high in fruits and vegetables was associated with the lower risk of VAD whereas elevated CRP and/or AGP increased the risk of VAD.
The micronutrient content (provitamin A carotenoids, tocopherols, ascorbic acid and
minerals which are iron, calcium, magnesium and zinc) of the selected ILVs commonly
consumed in the study areas was high. Beta-carotene concentration was high ranging
between 2.91 and 4.84 mg/100 g (fresh weight) in ILVs including Amaranthus spp,
Sesamum angustifolium and Corchorus trilocularis. This amount could provide more than
50% of the recommended nutrient intake (RNI) for vitamin A. The level of iron was high
(34.5–60.4 mg/100 g) in ILVs including Cleome hirta and Sonchus luxurians and capable
of providing more than 50% of RNI for iron. Amaranthus ssp. had high levels of calcium,
magnesium and zinc and these amounts could provide 85%, 207% and 21% of RNI per
100 g, respectively. Cleome hirta and Cleome gynandra had high ascorbic acid content
more than 15 mg/100 g, and could provide 34 –35% of RNI for ascorbic acid. Sesamum
angustifolium was the only ILV with high tocopherol content (7.34 mg α-TE/100 g). The
highest phytate concentration was found in Amaranthus ssp., which could negatively affect
its role as a very good source of minerals. After the implementation of an integrated home
gardening intervention, the prevalence of anaemia decreased from 42.7’% to 30.6%, and
vitamin A deficiency from 24.5% to 0.4% (p<0.001). Consumption of vegetables, fruits
and legumes significantly increased from baseline to the end-line survey (87% vs 98%,
63% vs 69% and 76% vs 87%), p<0.001, respectively. Moreover, households that reported
to grow vegetables increased from 76.6% to 82.1%, (p<0.05); awareness on pocket
gardening increased from 21.6% to 92.9%, (p< 0.001) and proportion of households
practicing pocket gardening increased from 3% to 76.4% (p < 0.001) from baseline to the
end-line survey.
Conclusions: School children in the districts of Chamwino and Kilosa, Tanzania, are
simultaneously affected by low energy intake, anaemia, infections such as malaria,
micronutrient deficiencies, and inadequate diets. Moreover, significant variations in
micronutrient status and dietary habits between districts were observed. Long-term
nutritional deficits as reflected by high prevalence of stunting and current micronutrient
status, especially vitamin A, iron and zinc, underlines the importance of targeting school
children in national nutrition and health surveys for nutrition assessment and surveillance.
The analysed indigenous leafy vegetables can potentially make a considerable contribution
towards the requirements for nutrients, particularly vitamin A and iron, which are
micronutrients of public health significance among school children in the study areas. The
significant decrease in the prevalence of anaemia and vitamin A deficiency among the
school children during post intervention phase, suggests the potential of integrating
nutrition sensitive interventions such as home gardening and nutrition education for better
nutritional outcomes. Moreover, programs that reduce infectious diseases and improve
hygiene are essential to ensure quality utilization of nutrients in the body.
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Keywords
Micronutrient, Indigenous vegetables, School children