Variation in arsenic bioavailability in rice genotypes using swine model: An animal study

- Arsenic (As) concentrations in rice varies significantly based on genotypes.
- Bioavailability of As from rice is crucial to understand the human health risk.
- Inorganic As has five times higher bioavailability than organic As.
- Rice As bioavailability varied between 25% and 94% based on varieties.
- Salt tolerance and brown rice have higher As content but lower bioavailability.

An in vivo assay using swine was used to measure the absolute bioavailability (AB) of As from cooked rice of twelve genotypes commonly grown in Bangladesh. An assessment of both total As in rice and its bioavailability is crucial for estimating human exposure following dietary intake by the local community. Average As concentrations in each rice genotype ranged from 108 ± 4 μg/kg to 580 ± 6 μg/kg. Arsenic speciation shows that most of the rice genotype contains 73 to 100% inorganic As. Swine were administered with As orally and via intravenous method, i.e. injection and fed certain common Bangladeshi rice genotypes (cooked). Swine blood As levels were measured to calculate As bioavailability from rice. Pilot studies shows that for As(III) and As(V), 90.8 ± 12.4% and 85.0 ± 19.2% of the administered oral dose was absorbed from the gastrointestinal tract whereas organic As was poorly absorbed resulting in low bioavailability values 20.2 ± 2.6% (MMA) to 31.2 ± 3.4% (DMA), respectively. These studies demonstrates that rice genotypic characters influenced As bioavailability in rice grown in As-contaminated areas and the bioavailability varied between 25% and 94%. Arsenic in salt tolerant rice genotypes Binadhan-10 and BRRI dhan47 as well as brown rice genotypes Kheali Boro and Local Boro has lower bioavailability (< 50%) compared to other rice genotypes. The most commonly cultivated and consumed variety (BRRI dhan28) has As bioavailability of 70%, which poses a significant risk to consumers. Calculation of maximum tolerable daily intake (MTDI) for humans due to consumption of rice based on bioavailability data was higher than those calculated based on inorganic and organic As concentration in rice genotypes.

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