Rice bran 鈥� a so-called 鈥渟uperfood鈥� 鈥� might contain dangerous amounts of a natural poison.
A new study suggests that rice bran, the shavings left over after brown rice is polished to produce white rice grains, contains 鈥渋nappropriate鈥� levels of arsenic. Andrew Meharg at the University of Aberdeen, UK, and colleagues found that the levels of arsenic in rice bran products available on the internet and used in food-aid programmes funded by the US government would be illegal in China 鈥� the only country in the world to have standards for how much arsenic is permissible in food.
Meharg鈥檚 team are calling on the European Union and the US to follow China鈥檚 example and update food standards for arsenic.
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Arsenic is a natural carcinogen, present in drinking water around the world including in Australia, the US and many developing countries.
In previous work, Meharg has shown that brown rice contains more arsenic than polished white rice ().
Nutritional drink
In the new study, Meharg and colleagues purchased brown rice from China and Bangladesh and polished part of it in the same way that it would be to produce commercial white rice. They found that 1 kilogramme of brown rice contained on average 0.76 mg of arsenic in its toxic inorganic form. The rice also contained some non-toxic, organic arsenic. The polished white rice grains contained 0.56 mg inorganic arsenic per kg, whereas the rice bran contained 3.3 mg per kg on average.
On the surface, this appears to be good news: the bran shavings are usually discarded except in Japan, where they are used in traditional pickling recipes. But in recent years a number of rice-bran products have come onto US and European markets, mainly targeted at health-food consumers. They are labelled 鈥渟uperfoods鈥�: the bran is high in antioxidants, vitamins, mineral nutrients and fibre. Producers say it is the largest wasted agricultural food resource on the planet, with 60 million metric tonnes of it discarded worldwide each year.
Some companies have produced a powdered version with a long shelf life at room temperature. Mixed with water, these 鈥渞ice-bran solubles鈥� make a nutritional drink and have been distributed as food aid to malnourished children in Malawi, Guatemala, Nicaragua and El Salvador. There are plans to further expand the aid programmes in Latin America, India and the Caribbean.
Meharg and his colleagues purchased nine commercial rice-bran products online, including rice-bran solubles from NutraCea, a company that participates in food-aid programmes, and analysed their arsenic content. The products contained between 0.48 mg/kg and 1.16 mg/kg of inorganic arsenic. China recently updated its standards, and set the limit to 0.15 mg of inorganic arsenic per kg of food.
Risk analysis
鈥淭he arsenic concentrations reported are worrisome, but the risk assessment is complex,鈥� says , professor of environmental health at Harvard University鈥檚 School of Public Health.
Indeed, 鈥渟afe鈥� standards for arsenic intake are controversial. The risk of skin, lung, bladder and kidney cancer increases proportionally with arsenic intake, which has lead toxicologists to the conclusion that there is no 鈥渟afe鈥� limit. But risks must be weighed against the benefits gained from drinking water and eating certain foods that contain the poison.
NutraCea has carried out a pilot project distributing their rice-bran solubles to 67,000 pre-school children in Guatemala. They monitored the nutritional state of 150 children. Whereas at the beginning of the trial, 37% were deemed malnourished, that dropped to 5% after taking 15 g of the rice bran 5 days a week for 6 months. The project was funded by the US Agency for International Development and the .
, an environmental toxicologist at the Karolinska Institute in Sweden who has done extensive studies on the health effects of arsenic believes the nutritional benefits do not necessarily outweigh the risks, given the availability of other supplements. 鈥淩ecent reports indicate increased fetal and infant mortality due to fairly low-level arsenic exposure via drinking water,鈥� says Vahter. Arsenic also impairs brain development and impairs the body鈥檚 ability to repair DNA.
Unwanted substances
鈥淩ice-bran solubles are not the only way of getting nutrients to malnourished children,鈥� argues Meharg. 鈥淚f aid agencies want to go down the bran solubles route why not wheat, oat or barely bran solubles. All these crops have ten times less total arsenic than rice and are just as nutrient rich.鈥�
鈥淥ne would expect dietary supplements to be virtually free of unwanted substances like arsenic, especially when aimed at children, who are particularly vulnerable to arsenic,鈥� says Grandjean.
Drinking water limits on arsenic levels are more widespread than food limits, despite animal studies showing that the body does not distinguish between arsenic derived from food and from drink. Water limits tend to be based on the World Health Organization鈥檚 鈥減rovisional鈥� guideline limit of 0.01 mg of arsenic per litre of drinking water 鈥� although the WHO itself admits that 鈥渂ased on health criteria鈥� the guideline would be less than this. It says the value is restricted by measurement limitations, hence its provisional nature.
According to China鈥檚 standards, all of the rice-bran products tested by Meharg would be illegal. According to the UK鈥檚 50-year-old standards, two of the nine products are safe 鈥� yet all can be purchased online in the UK. The US has no standards for arsenic levels in food, and has a limit of 0.01 mg/l in drinking water.
鈥淲e totally agree with the overall message that it is important to set standards for inorganic arsenic in our food,鈥� comments Walter Goessler, an arsenic expert at the Karl-Franzens University in Austria.
鈥淩ice-bran solubles are being produced by commercial companies who profit from this commodity,鈥� says Meharg.
At the time of going to publication, NutraCea had not replied to New 杏吧原创鈥榮 request for comment.
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