What was studied?
The study investigated the effectiveness of different rice cooking methods in reducing the concentration of inorganic arsenic (iAs), a Group 1 carcinogen, while preserving essential nutrient elements in both brown and white rice. With a focus on practical, home-friendly approaches, the researchers compared four absorption-based cooking treatments: unwashed and absorbed (UA), washed and absorbed (WA), pre-soaked and absorbed (PSA), and a novel parboiled and absorbed (PBA) method. The study’s overarching aim was to identify an optimal cooking technique that maximizes iAs removal from rice, thereby reducing dietary exposure risks, but does so without significant depletion of critical nutrients like phosphorus, potassium, magnesium, zinc, and manganese. The researchers performed extensive elemental analysis and arsenic speciation using ICP-MS and LC-ICP-MS, respectively, and calculated the margin of exposure (MOE) to assess the health implications of consuming rice processed by each method.
Who was studied?
The study examined six commercially available rice types commonly sold in the United Kingdom: three brown rice varieties (Thai Brown, short grain brown, and brown basmati) and three white rice varieties (everyday long-grain, pudding rice, and sushi rice). These rice types were selected from a larger batch previously analyzed for high iAs content to ensure that the results would be relevant for risk mitigation in populations at greater risk of arsenic exposure. Each treatment was replicated three times per rice type, resulting in robust comparative data. The consumer populations considered in the risk assessment included UK infants, children, and adults, reflecting a wide range of dietary exposures and body weights.
Most important findings
| Critical Points | Details |
|---|---|
| PBA method most effective for iAs removal | The parboiled and absorbed (PBA) method reduced iAs by 54% in brown rice and 73% in white rice compared to raw rice. |
| Impact on margin of exposure (MOE) | PBA increased MOE by 3.7 times for white rice and 2.2 times for brown rice, significantly lowering health risk across all ages. |
| Effect of other absorption methods | Washing and pre-soaking prior to absorption cooking reduced iAs significantly only in white rice, not brown rice. |
| Nutrient retention | Brown rice retained more nutrients than white rice under all absorption methods; PBA did not cause significant zinc loss. |
| Losses of magnesium, potassium, manganese | Some reduction of Mg, K, and Mn occurred, particularly in white rice, but losses were generally less than excess water methods. |
| Organic arsenic (oAs) unchanged | Cooking methods did not significantly affect less harmful organic arsenic species. |
| Broader safety for vulnerable populations | With PBA, maximum safe daily rice consumption increased (e.g., for infants and children) compared to raw rice. |
Key implications
The PBA method is a practical, home-friendly cooking approach that can be adopted globally to substantially reduce dietary inorganic arsenic exposure from rice without significant nutrient loss. For heavy metal certification programs, recommending or requiring PBA can enhance consumer safety, especially for sensitive groups such as infants and children, while preserving essential micronutrients.
Citation
Menon, M., Dong, W., Chen, X., Hufton, J., & Rhodes, E.J. (2021). Improved rice cooking approach to maximise arsenic removal while preserving nutrient elements. Science of the Total Environment, 755, 143341. https://doi.org/10.1016/j.scitotenv.2020.143341
Arsenic is a naturally occurring metalloid that ranks first on the ATSDR toxic substances list. Inorganic arsenic contaminates water, rice and consumer products, and exposure is linked to cardiovascular disease, cognitive deficits, low birth weight and cancer. HMTC’s stringent certification applies ALARA principles to protect vulnerable populations.