Addition of Zinc to Soaking Water during Parboiling Increases the Zinc Content of Bangladeshi Rice

Abstract

Objectives: In Bangladesh, zinc deficiency affects 45% of preschool children and 57% of women. As zinc deficiency is linked to child growth stunting, diarrheal disease, pneumonia, and increased risk of child mortality, large-scale programs for its prevention are required. Most rice produced in Bangladesh is parboiled and this presents a technical opportunity to increase rice zinc content by adding zinc during soaking. The objective of this study was to evaluate the increase in zinc content achievable by this strategy in milled Bangladeshi rice using local parboiling conditions, and its potential effect on adequacy of zinc intakes. Methods: A major local rice variety (BR29) and zinc sulfate were used. Paddy was steamed for 2 minutes, soaked in distilled, deionized water for 9 hours with addition of 0, 100, 150, 200, or 300 mg zinc/kg paddy. Drained paddy was steamed in a pressurized autoclave before drying and milling. Zinc content was determined by X-Ray Fluorescence. Results: Rice zinc content was 12.3, 16.0, 16.7, 21.6, and 23.6 mg/kg dry weight, respectively, where the highest level represents a 92% increase over the control. Using existing dietary intake data from two districts, we estimated that if parboil-fortified rice with 300 mg/kg zinc were consumed by 70% of the population, the prevalence of inadequate intakes would decrease from 34 to 16% among preschool children and 98 to 43% among women. Conclusions: This strategy has potential to substantially decrease the prevalence of dietary zinc deficiency in Bangladesh, although the technical feasibility of implementing in large-scale mills requires further study.