Contribution of groundwater iron to cooked rice and the implication on the recommended iron intakes: a cross-sectional study in Bangladesh

Groundwater iron varies geographically and iron intake through drinking water can minimise iron deficiency (ID). Rice, a major share of daily meals (∼70% of total energy) in Bangladesh, absorbs a substantial amount of water. This study aimed to estimate the contribution of groundwater iron entrapped in cooked rice and its implications on the recommended iron intake. A cross-sectional study was conducted among 25 households, selected by the iron content of their drinking groundwater source in Sirajganj district, Bangladesh. Each household pre-supplied with 600 g of raw rice (300 g for each cooking), was instructed to cook 'water-draining rice' (WDR) and 'water-sitting rice' (WSR). Using atomic absorption spectrophotometry, iron content in filtered and non-filtered water was measured as 0.4 ± 0.2 mg/L and 6.1 ± 2.0 mg/L, respectively. After adjusting for water filtration, the weighted mean of total iron content in WDR and WSR was 6.18 mg and 5.70 mg, respectively. Assuming the average rice intake, iron content in WDR and WSR fulfilled approximately 98.15% and 90.62% of the average requirement for non-pregnant and non-lactating women (NPNL). The water-entrapped iron in cooked WDR and WSR fulfilled about 23.77% and 20.4% of Recommended Dietary Allowances, and 52.83% and 45.30% of Estimated Average Requirements, respectively in NPNL women, suggesting that groundwater entrapped in cooked rice is an influential dietary iron source. The substantial amount of iron from cooked rice can make an additional layer to the environmental contribution of iron in this setting with the potential to contribute ID prevention.