Arsenic and Mercury in Rice: New Research from Dartmouth College
February 28, 2018
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Updated summary test report for arsenic is available after login at https://www.glutenfreewatchdog.org/product/arsenic-summary-report-updated-2018/679
Updated summary test report for mercury is available after login at https://www.glutenfreewatchdog.org/product/mercuryricegrain-combined-data-2018-update-/680
The researchers from Dartmouth College who tested rice products for arsenic and mercury for Gluten Free Watchdog have just published a new article in the journal Food Chemistry entitled, “Essential micronutrient and toxic trace element concentrations in gluten containing and gluten-free foods” (abstract available at https://www.sciencedirect.com/science/article/pii/S0308814618301341). Among other micronutrients and trace elements, they assessed rice and rice-based products for arsenic and mercury.
Arsenic findings: Researchers found that “the total arsenic concentration in whole grain rice, rice flour and processed foods containing rice was significantly higher than non-rice flours and processed foods based on other grains.” In addition, brown rice and enriched white rice had significantly higher concentrations of total arsenic than white rice that was not enriched. The amount of inorganic arsenic was also significantly higher in brown rice than white rice—both enriched and unenriched varieties. According to the researchers, “inorganic arsenic accumulation in bran layers of the rice grain is a likely explanation for the higher inorganic arsenic concentrations measured in brown rice. However, the reason why enriched white rice grain contains higher organic arsenic concentrations than brown or non-enriched white rice is not clear and may be an artifact of the small sample size of each grain type.”
Mercury findings: Results were low for all foods tested, including rice. However, researchers found that “food containing rice had significantly higher mercury concentrations than those based on wheat or other grains.” Mercury concentrations did not differ significantly between rice types—brown, unenriched white, and enriched white.
Why does arsenic and mercury accumulate in rice? According to the researchers, “Like arsenic, the presence of methylmercury in rice is due to the practice of growing rice in flooded soils.”
Bottom line: Gluten Free Watchdog asked Tracy Punshon, one of the researchers for her main take away points from the study:
- Eat as wide a variety of gluten-free grains as possible
- Pay attention to the rice and rice ingredient content of gluten-free foods
At Gluten Free Watchdog we echo the above recommendations.