Factors influencing micronutrient status in school children and role of indigenous vegetables for improving micronutrient intake in rural Tanzania

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Sokoine University of Agriculture


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.



Micronutrient, Indigenous vegetables, School children