Vitamin D2026-06

Effect of School-Based Physical Activity and Multi Micronutrient Supplementation on Micronutrient Concentrations Among Tanzanian Schoolchildren: Secondary Outcomes from the KaziAfya Cluster-Randomized Controlled Trial.

Minja Elihaika G, Mrimi Emmanuel C, Mponzi Winfrida P, Beckmann Johanna et al. — Nutrients

Summary

This study investigated whether school-based physical activity and multi-micronutrient supplements could improve nutrient levels in Tanzanian schoolchildren. While physical activity showed some benefits for zinc, the findings for vitamin D were very limited and inconclusive due to a small sample size. Therefore, this study cannot definitively conclude the impact of these interventions on vitamin D status.

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Key points

The study examined the impact of school-based physical activity and multi-micronutrient supplements on children's nutrient levels in Tanzania.
Physical activity interventions were linked to a reduced risk of zinc deficiency among schoolchildren.
Multi-micronutrient supplementation alone did not show significant benefits for zinc or iron status in this study.
The findings for vitamin D were inconclusive because only a very small number of children had valid measurements for this nutrient.

What the study looked at

### What question the study asked Researchers wanted to know if school-based programs, including physical activity and multi-micronutrient supplements, could improve the nutritional status of children in Tanzania. They specifically looked at levels of important micronutrients like zinc, iron, and vitamin D. ### How it was studied The study involved schoolchildren aged 6-12 in Tanzania and used a cluster-randomized controlled trial design. Children were divided into four groups: one received physical activity, another received multi-micronutrient supplements, a third received both, and a control group received a placebo. Their micronutrient levels were measured at the start and again after 26 months. ### What it found The study observed that school-based physical activity was associated with a lower chance of zinc deficiency, whether delivered alone or with supplements. However, multi-micronutrient supplementation alone did not significantly improve zinc or iron status. Crucially for vitamin D, the analysis was based on a very small number of children, meaning the results for vitamin D are not conclusive and require further research.

Dietary takeaway

This study's findings regarding vitamin D are not definitive due to the small number of participants analyzed for this specific nutrient. While maintaining adequate vitamin D is important for overall health, this particular research does not offer clear guidance on how school-based physical activity or multi-micronutrient supplements impact vitamin D levels or inform everyday food choices for this nutrient. More research is needed to understand these connections.

Abstract

Micronutrient deficiencies and physical inactivity can adversely affect child growth and development. This study assessed the effects of school-based physical activity and multi-micronutrient supplementation on micronutrient status among schoolchildren in Kilombero district, Tanzania. In a cluster-randomized trial, children aged 6-12 years were allocated to physical activity, multi-micronutrient supplementation, combined physical activity plus supplementation, or placebo control. Anthropometric and biochemical assessments were conducted at baseline, 14 months, and 26 months. Dried blood spot samples were available for 923 children at baseline. Complete-case analyses used biomarker-specific subsamples with valid baseline and 26-month measurements. The primary complete-case sample included 243 children with valid paired measurements for zinc and serum transferrin receptor; vitamin D analyses were restricted to 52 children because of missing or invalid samples. At baseline, iron and vitamin D deficiencies were common, affecting 42.8% and 39.9% of children, respectively, while zinc deficiency affected 11.9%. At 26 months, allocation to the physical activity intervention was associated with lower odds of zinc deficiency, both when delivered alone (OR = 0.16) and when combined with supplementation (OR = 0.57). Supplementation alone was not significantly associated with reduced zinc deficiency. Iron status did not differ between intervention groups. Vitamin D findings should be interpreted with caution because analyses were based on a very small biomarker-specific subsample. School-based physical activity, alone or combined with multi-micronutrient supplementation, was associated with lower odds of zinc deficiency among Tanzanian schoolchildren. Supplementation alone showed no clear benefit for zinc or iron status. Vitamin D findings remain inconclusive because of substantial biomarker-specific missingness. Future trials should strengthen adherence monitoring, biomarker follow-up, and repeated assessment of dietary and contextual factors.

View on PubMed →DOI: 10.3390/nu18121980