Paddy rice is the carbohydrate staple of half the world yet it is the main source of exposure to the class-one, non-threshold carcinogen inorganic arsenic (Asi). International and national bodies are in the process of setting standards for inorganic arsenic in rice due to the fact sub-populations are exposed to levels that are associated with negative health consequences.
US legal standards
The UN WHO has just set, in 2014, advisory levels of Asi in polished (i.e. white) rice grain at 0.2 mg/kg, while the European Union and the US is in the process of setting legal standards for inorganic arsenic in rice based products.
As part of the study, researchers at Queen’s tested two methods of percolating technology, one where the cooking water was recycled through condensing boiling-water steam and passing the distilled hot water through the grain in a lab setting, and one where tap water was used to cook the rice in an off-the-shelf coffee percolator .
Both approaches proved effective, with up to 85% of arsenic removed from a variety of different rice types and brands, including wholegrain and white.
The scientists concluded a shop-bought coffee percolator is the best method for removing the carcinogen, inorganic arsenic, from all types of rice, including white and wholegrain.
Andy Meharg, professor of Plant and Soil Sciences, Queen's Institute for Global Food Security said the breakthrough discovery is significant as offers an alternative to decreasing inorganic arsenic in the diet.
“In our research we rethought the method of rice cooking to optimise the removal of inorganic arsenic and we discovered by using percolating technology, where cooking water is continually passed through rice in a constant flow, we could maximise removal of arsenic,” he said.
Heart disease, diabetes & nervous system damage
“Chronic exposure to inorganic arsenic can cause a range of health problems including developmental problems, heart disease, diabetes and nervous system damage.
“However, most worrying are lung and bladder cancers. This breakthrough is the latest example of the commitment of researchers at Queen’s to changing lives and advancing knowledge that will have a lasting impact around the globe.”
Queen’s is now seeking a patent for the development of a bespoke rice cooker based on a percolation system.
Rice has, typically, 10 times more inorganic arsenic than other foods and according to the European Food Standards Authority, people who eat a lot of rice, as is the case in many parts of the developing world, are exposed to worrying concentrations. Children and infants are of particular concern as they eat, relatively, three times more rice than adults – baby rice being a popular food for weaning – and their organs are still developing.
Market rice was purchased from major UK retailers in the city of Belfast, or purchased online through UK retailers. Of the 41 samples tested in the study, two were generically labeled as being from the EU, 11 from Spain, six from Italy, five from Thailand, five from France, two from Egypt, one from Japan, one from Australia, one from Lebanon, one from Pakistan, one from Turkey and five from the USA; with 13 being unpolished (wholegrain) and the rest polished.
Source: PLOS ONE
Title: ‘Rethinking Rice Preparation for Highly Efficient Removal of Inorganic Arsenic Using Percolating Cooking Water’
Author(s): Manus Carey, Xiao Jiujin, Júlia Gomes Farias, Andrew A. Meharg
Published: July 22, 2015