Rice in Asia: Too Little Iron, Too Much Arsenic

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> 13 Sep 2004 14:55:45 -0000

 

> Rice in Asia: Too Little Iron, Too Much

> Arsenic

> press-release

>

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>

> ISIS Press Release 13/09/04

> Rice in Asia: Too Little Iron, Too Much Arsenic

> ************************************

>

> Asians are getting too little iron and too much

> arsenic from

> soil and water. Unfortunately the remedy for one

> problem may

> increase the impact of the other. The challenge is

> to find a

> remedy that takes care of both problems, says Prof.

> Joe

> Cummins.

>

> A fully referenced

> http://www.i-sis.org.uk/full/RIATLITMAFull.php

> version of this article is posted on ISIS members'

> website.

> Details here http://www.i-sis.org.uk/membership.php.

>

> Problem of too little iron

>

> It has been estimated that 40% of the world's women

> suffer

> some degree of iron deficiency. Anaemia is

> associated with

> learning difficulties in children, increased

> susceptibility

> to disease and reduced work capacity. Pre-menopausal

> women

> are most severely affected by iron deficiency, while

> men

> tend to retain iron (as indicated below, an iron

> overload

> diet may increase risk of cancer in males).

> Increasing iron

> in the diet is a desirable goal and rice is the

> preferred

> crop for genetic modification (GM) to increase iron

> in the

> diet, especially in Asia.

>

> Researchers from the Japanese Electrical Power

> Research

> Institute increased the iron content of rice

> threefold by

> adding a seed-specific ferritin (an iron storage

> protein)

> from soybean under the control of a rice seed

> storage

> protein promoter. But although the iron content of

> the rice

> grain was increased significantly, there has been

> concern

> that the ferritin-bound iron may not be readily

> available in

> the digestive tract of mammals.

>

> A Swiss research group transformed rice with a

> ferritin gene

> from snap beans under the control of a rice storage

> protein

> promoter accompanied by a fungal phytase gene also

> under the

> control of the storage protein promoter. The phytase

> gene

> produces an enzyme that increased iron availability

> during

> digestion. An endogenous rice metallothionein (a

> ubiquitous

> metal-binding cellular protein) was over-expressed

> in the

> transgenic rice to further aid in iron digestion by

> providing a form of iron readily taken up in the

> gut. An

> antibiotic resistance marker gene for the antibiotic

>

> hygromycin was added during the transformations of

> the rice.

> The iron content of the rice was doubled while, in

> contrast

> to the Japanese study, the iron was more readily

> available

> during digestion. The Swiss study was supported by

> the

> Rockefeller Foundation.

>

> However, iron overload is a significant problem in

> males -

> it may lead to a condition called hemochromatosis in

> which

> the liver and other organs may be damaged, causing

> liver

> cancer or colorectal cancer. As much as one person

> in a

> hundred may carry a mutation (hereditary

> hemochromatosis)

> that makes them sensitive to iron overload at

> relatively

> modest iron intake levels. There is an association

> between

> increasing iron stores and risk of cancer.

>

> In areas of the world where iron deficiency is

> commonplace,

> iron-enriched rice may prove beneficial, but the

> same iron-

> enriched rice could prove to be a liability in areas

> where

> iron intake is at high levels. Iron overload should

> be

> considered in the distribution of iron-enhanced

> rice. The

> need for labeling of iron rich rice products is

> evident.

>

> The Arsenic Problem

>

> Asia is facing a growing crisis in the use of

> arsenic-

> contaminated ground water for drinking and in

> irrigation of

> rice paddies. Arsenic pollution is a severe problem

> over

> Bangladesh/West Bengal and in the Red River Delta of

> Vietnam

> but it is also a chronic problem in Taiwan, China

> and

> Thailand. Most arsenic pollution is of natural

> origin,

> amplified by drawing water from contaminated deep

> aquifers,

> but China has arsenic pollution from burning high

> arsenic-

> containing coal. Arsenic has been shown (from

> studies in

> Taiwan) to cause cancer and circulatory problems at

> very low

> levels, the cancers include cancers of liver, lung,

> bladder

> and kidney. It has been estimated that the arsenic

> pollution

> of drinking water in the United States causes an

> average of

> 3000 cancer cases per year.

>

> In Asia, the arsenic problem is amplified by the

> pollution

> of rice, the primary food source. Arsenic has been

> accumulating in paddy soil, resulting in the

> contamination

> of the rice grain. Rice contributes to an estimated

> 30 to

> 60% of the dietary intake of arsenic in polluted

> regions.

>

> There is hope that rice strains can be selected that

> take in

> less arsenic than the varieties of rice currently in

> use. It

> has been found that arsenic is sequestered on

> iron-plaques

> (rust-like deposits) on the surface of roots of rice

>

> varieties that accumulate reduced levels of arsenic

> in

> grain. Rice paddies will continue to be polluted

> with

> arsenic in the soil because there is no practical

> method

> known to remediate the vast expanses of polluted

> soil.

> Breeding rice to reduce grain pollution seems to be

> an

> effective first step towards improving the diet in

> polluted

> areas and varieties with reduced grain content of

> arsenic

> are known.

>

> Iron and arsenic interact in rice

>

> There is a potential conflict in governmental and

> foundation

> programmes to develop and disseminate high-iron

> grain to

> alleviate iron-deficiency among rice consumers. The

> high-

> iron rice varieties currently under development

> include

> amplifying the expression of ferritin in grain and

> solubilising iron for uptake in the gut using a

> phytase gene

> from a fungus [3]. Arsenic reduced the concentration

> of iron

> in the plant in rice varieties that form

> iron-plaques on the

> roots; but in varieties lacking the iron-plaques,

> iron

> uptake was not reduced in the presence of arsenic.

> It

> appears that the iron-plaques sequester both iron

> and

> arsenic, so that both iron and arsenic are reduced

> in the

> rest of the plant.

>

> The iron-enhanced grains designed to combat

> iron-deficiency

> are therefore, very likely to increase grain-arsenic

> levels

> in arsenic-polluted areas of Asia because the

> arsenic will

> not be sequestered on the root surface in iron

> plaques but

> instead will be taken into the shoot and end up in

> the rice

> grain. It seems a devil's bargain: either to make

> high-iron

> rice available at the cost of elevated arsenic or to

> make

> low-arsenic rice available without providing an

> alternate

> source of dietary iron.

>

> But this dilemma only exists if one insists on GM

> rice as

> the only solution. It disappears instantly when one

> realizes

> that iron can be provided through other sources,

> such as

> beans and lentils which can easily be grown, and are

> rich

> sources of other essential nutrients besides.

>

>

>

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