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Rice is the staple food of many people, but it can contain dangerous levels of arsenic PHOTO CREDIT: Nature

Preparing product in coffee machine can halve levels of arsenic 

COOKING rice by repeatedly flushing it through with fresh hot water can remove much of the grain’s stored arsenic, researchers have found — a tip that could lessen levels of the toxic substance in one of the world’s most popular foods.

Billions of people eat rice daily, but it contributes more arsenic to the human diet than any other food. Conventionally grown in flooded paddies, rice takes up more arsenic (which occurs naturally in water and soil as part of an inorganic compound) than do other grains.

High levels of arsenic in food have been linked to different types of cancer, and other health problems. Andrew Meharg, a plant and soil scientist at Queen’s University Belfast, United Kingdom (UK), wondered whether cooking the grain in a different way might help to lessen the health risk.

The standard method for making rice — boiling it in a pot until it soaks up all the liquid — binds into place any arsenic contained in the rice and the cooking water. On the basis of earlier work, Meharg and his colleagues knew that arsenic levels drop when rice is thoroughly rinsed and then cooked in an excessive amount of water.

The method helps even when the cooking water contains arsenic. Meharg and colleagues found that using this method with increasing proportions of water removed progressively more arsenic — up to a 57 per cent reduction with a ratio of 12 parts water to one part rice. That result confirmed that the arsenic is ‘mobile’ in liquid water, and thus can be removed.

The team then cooked rice in an apparatus that continually condenses steam to produce a fresh supply of distilled hot water, and in an ordinary coffee percolator with a filter, which allows cooking water to drip out of the rice.

Testing the rice before and after cooking showed that coffee-pot percolation removed about half the arsenic, and that the lab apparatus removed around 60 to 70 per cent.

In some cases, the technique removed as much as 85 per cent of the substance, depending on the type of rice used. The findings are reported in PLoS ONE.

Billions of people eat rice daily, but it contributes more arsenic to the human diet than any other food. Conventionally grown in flooded paddies, rice takes up more arsenic (which occurs naturally in water and soil as part of an inorganic compound) than do other grains. High levels of arsenic in food have been linked to different types of cancer, and other health problems…arsenic levels drop when rice is thoroughly rinsed and then cooked in an excessive amount of water. The method helps even when the cooking water contains arsenic…using this method with increasing proportions of water removed progressively more arsenic — up to a 57 per cent reduction with a ratio of 12 parts water to one part rice. That result confirmed that the arsenic is ‘mobile’ in liquid water, and thus can be removed.

Meharg does not expect people to start cooking rice in their coffee machines. “We just took something that’s in everybody’s kitchen and applied it to show a principle,” he says.

He sees the research as a proof of concept that could feed the development of simple, inexpensive rice cookers that lower arsenic concentrations. The risk of arsenic poisoning is greatest for consumers who eat rice several times a day. In Bangladesh, where rice is a staple and the water is also naturally high in arsenic, people are particularly vulnerable.

Parboiling facilities in the country process rice by pre-cooking, drying and husking the grain. These processes offer the opportunity to intervene on a commercial scale with cookers that would reduce arsenic levels — something that Meharg plans to do.

The same technique could also help companies elsewhere to lower arsenic levels in baby cereals and other products that use pre-cooked rice. Rice-based baby foods often contain high levels of arsenic, a double-whammy for small children, who consume proportionately more of the substance for their body size.

In the long term, the best strategies for removing arsenic from rice will come from ongoing efforts to breed low-arsenic strains and alter growing techniques, says Margaret Karagas, an epidemiologist at Dartmouth College in Hanover, New Hampshire. But, she says, “This paper is really interesting because it is offering a short-term solution to the problem.

It’s giving people an opportunity to reduce the arsenic burden of their rice.” Arsenic is a natural occurring element that is ubiquitous in the environment. It is present primarily as inorganic arsenic, which is highly toxic.

What sets rice apart is that it is the only major crop that is grown under flooded conditions. It is this flooding that releases inorganic arsenic, normally locked up in soil minerals, which makes it available for the plant to uptake.

Rice has, typically, ten times more inorganic arsenic than other foods and, as the European Food Standards Authority have reported, people who eat a lot of rice are exposed to worrying concentrations. Chronic exposure 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. Children of most concern The first food that most people eat is rice porridge, thought suitable for weaning as rice is low in allergens, has good textural properties and tastes bland.

As babies are rapidly growing they are at a sensitive stage of development and are known to be more susceptible to inorganic arsenic than adults. Babies and young children under five also eat around three times more food on a body weight basis than adults, which means that, relatively, they have three times greater exposures to inorganic arsenic from the same food item.

Babies more exposed. Rice biscuit by Shutterstock. The rice product market for young children, which includes biscuit crackers and cereals is booming. If the child is gluten intolerant then rice breads and rice milks can be added to this list. Gluten intolerant adults are also high rice consumers, as are those people of South-East Asian origin.

Rice milk is so high in inorganic arsenic that the UK Food Standards Agency issued the advice that children under the age of four-and-a-half should not drink rice milk. Despite this, you would be hard-pressed to locate this advice on product packing or displays.

Where are the regulations? While there is tight regulation around inorganic arsenic in our water supplies in Europe but none for food, yet in Europe only 5% of our inorganic arsenic comes from water and 95% from food. Bottled water in the EU is around 50 times lower in inorganic arsenic water concentrations than rice.

Therefore, you would need to drink five litres of water to get the equivalent arsenic dose of eating a small 100g (dry weight packet) portion of rice. The failure to regulate rice in food is unsustainable and needs to be rectified. Milling means less in white rice.

Takeaway, CC BY-SA The World Health Organisation and the Food and Agriculture Organisation of the UN have just announced guidelines for inorganic arsenic in rice: 200 parts per billion for white rice and 400 parts per billion (ppb) for brown rice.

Brown rice is higher in inorganic arsenic than white as arsenic is concentrated in the bran that is removed by milling to produce white rice. The aim of these limits is to ensure that the bulk of the global rice supply falls below these thresholds rather than directly focusing on the risk inorganic arsenic poses to humans – the particular dangers for children for example.

Without doing this, the WHO thresholds are basically meaningless. They certainly do not protect those at greatest risk such as children and the high rice consuming countries of south-east Asia. Further pronouncements by the European Union and the US Food and Drug Administration are imminent.

Let us hope they take a more enlightened view than the WHO and set standards based on protecting human health. It is only when appropriate standards are set that the rice industry can proactively develop plans to remove arsenic from rice to meet those standards.

Standards need to be set to protect those most at risk and 50 ppb for children and 100 ppb for all rice products would be achievable with concerted effort of regulators and industry, though – as every dose of inorganic arsenic carries a risk – the lower the better.

What can be done now? There are a lot of practical solutions to remove inorganic arsenic from rice; from agricultural management and cultivar selection and breeding.

Sourcing rice from regions with lower grain inorganic arsenic concentrations – for example, basmati rice is two to three-fold lower in inorganic arsenic than rice from the European Union or from the US.

Cooking rice in a large excess of water also helps to remove inorganic arsenic. Changing dietary practice and food consumer advice to reduce rice in diets is also an option.

There are a range of gluten-free alternatives to rice, so rethinking baby foods is an obvious way to proceed. Top of this list of rice alternatives for baby foods and for breakfast cereals, biscuits and snack bars marketed at young children is oats, which have a range of other health-giving properties.



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