Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was studied?
This original research article investigated the risk and benefit of different rice cooking methods on the retention of essential elements and the removal of arsenic, a toxic heavy metal. The study focused on three popular cooking techniques: the contemporary method (1:3 rice-to-water ratio, water absorbed), the traditional Southeast Asian method (1:6 ratio, excess water discarded), and a parboiling method often used for Jollof rice in Nigeria (1:10 ratio, excess water discarded). Researchers quantitatively measured changes in total arsenic content and concentrations of essential elements (including calcium, cobalt, copper, iron, potassium, magnesium, manganese, molybdenum, nickel, selenium, and zinc) in rice, both before and after cooking. The percentage contribution of cooked rice to the recommended daily intake (RDI) of these essential elements was also calculated for each cooking method. By directly analyzing the outcomes of cooking on both arsenic removal and nutrient content, the study provides evidence critical for food safety and heavy metal certification programs, where balancing toxic element reduction with nutritional quality is a central concern.
Who was studied?
The study analyzed 24 rice samples sourced from the United Kingdom, Sri Lanka, Myanmar, and Nigeria, representing a diversity of origins and rice types (both whole grain and polished). The rice samples were collected from local stores or provided by collaborators in each country. Each rice sample underwent standardized rinsing and was then cooked according to the three selected methods. After cooking, samples were dried, milled, and subjected to elemental analysis using ICP-MS and ICP-OES for arsenic and essential nutrients. The study did not involve human subjects but focused on rice as a dietary staple, with an ingestion rate set at 100 g per day according to USDA recommendations for the calculation of dietary contributions. This approach was chosen to reflect real-world rice consumption patterns in different global contexts, as well as the varying risks and benefits for populations reliant on rice as a staple food.
Most important findings
| Critical Point | Details |
|---|---|
| Arsenic reduction by cooking method | Using the 1:3 rice-to-water method led to a modest 4.5% decrease in arsenic; the 1:6 method reduced arsenic by 30% (statistically significant, p=0.004), and parboiling (1:10) reduced arsenic by 44% (p<0.0001). The effect varied by rice origin: UK rice showed the greatest reduction, Nigerian rice the least, reflecting initial arsenic content and possibly genotype differences. |
| Essential element loss with increased water ratio | Essential elements (except iron, selenium, and copper) were significantly reduced when cooked with higher water ratios. For 1:6, the losses were potassium (50%), nickel (44.6%), molybdenum (38.5%), magnesium (22.4%), cobalt (21.2%), manganese (16.5%), calcium (14.5%), selenium (12%), iron (8.2%), zinc (7.7%), and copper (0.2%). Parboiling led to even greater losses for most elements except iron. |
| Nutritional implications for RDI | With the 1:6 method, the highest contribution to RDI was from molybdenum (154.7%) but most other elements contributed less than 35% to RDI: manganese (34.5%), copper (33.4%), selenium (13.1%), nickel (12.4%), zinc (10%), magnesium (8%), iron (6.3%), potassium (1.8%), and calcium (0.5%). Increasing the cooking water further reduced these values, except for iron, which increased with parboiling. |
| Arsenic and essential element correlation in raw rice | A significant positive correlation existed between arsenic content and molybdenum, magnesium, potassium, and iron in raw rice, suggesting that rice higher in arsenic might also be richer in some micronutrients. |
| Country-specific findings and risk | Six of the 24 raw rice samples exceeded the 0.2 mg/kg total arsenic threshold, and some retained levels above this after standard cooking. However, with 1:6 and parboiling, most samples were below this threshold, highlighting the public health value of excess-water cooking in high-risk regions. |
| Implications for heavy metal certification | The effectiveness of arsenic removal is accompanied by significant micronutrient loss, particularly in potassium, magnesium, and molybdenum. For certification, cooking practices must balance arsenic mitigation with nutritional adequacy, especially for populations dependent on rice for micronutrients. |
Key implications
For heavy metal certification programs, this study underscores that while excess-water rice cooking methods are effective in reducing arsenic exposure, they simultaneously cause substantial losses of essential elements. Certification protocols must therefore consider both heavy metal removal and micronutrient retention, particularly in settings where rice is a dietary staple and micronutrient deficiencies are common. This dual focus is essential for ensuring food safety and nutritional adequacy in vulnerable populations.
Citation
Mwale T, Rahman MM, Mondal D. Risk and benefit of different cooking methods on essential elements and arsenic in rice. Int J Environ Res Public Health. 2018;15(6):1056. doi:10.3390/ijerph15061056
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.
Heavy metals are high-density elements that accumulate in the body and environment, disrupting biological processes. Lead, cadmium, arsenic, mercury, nickel, tin, aluminum, and chromium are of greatest concern due to persistence, bioaccumulation, and health risks, making them central to the HMTC program’s safety standards.
