Loss of zinc from zinc-biofortified rice and conventional rice varieties due to various cooking techniques practiced in rural Bangladesh.

Abstract

Background: Zinc-biofortified rice has the potential to provide a sustainable solution for zinc deficiency, particularly in Asian countries where rice is the primary staple food. However, cooking of raw rice is associated with some loss of micronutrients, including zinc. The literature suggests that the amount of water used during cooking can influence the extent of micronutrient loss in both fortified and conventional rice varieties. This study aimed to estimate the cooking loss of zinc, iron, and phytate, as an important inhibitor of zinc, in zinc-biofortified and conventional rice varieties and to assess the effects of the amount of water used for cooking on the loss of these micronutrients. The secondary objective was to assess the impact on iron.

Results: Significant differences in zinc content were observed between the biofortified and conventional raw rice varieties. The median zinc content (interquartile range) was 19.7 (19.3, 20.2) mg kg⁻¹ in the biofortified variety and 18.7 (18.3, 18.7) mg kg⁻¹ in the conventional variety (P = 0.012). Cooking resulted in a significant reduction in zinc, iron, and phytate content with higher losses observed when cooking with 'excess' water (39% for zinc and 29% for iron) than when cooking with 'adequate' quantities of water (19% for zinc and 22% for iron).

Conclusion: This is the first study to estimate the cooking loss of zinc in zinc-biofortified rice in the Bangladeshi context and to estimate the effect of the amount of water used on this loss. Cooking resulted in a significant decrease in zinc and iron content, and there was a dose-response relationship between the amount of water used and the reduction in zinc and iron content. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.