Genetically Modified Foods:Are They a Risk to Human/Animal Health?

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Genetically Modified Foods:

Are They a Risk to Human/Animal Health?

By Arpad Pusztai, Ph.D.

An actionbioscience.org original article

 

http://www.actionbioscience.org/biotech/pusztai.html#Primer

 

Genetically modified (GM) crops and food are being grown and

consumed by the public, even though:

there is little scientific study about their health risks

safety test technology is inadequate to assess potential harm

they can carry unpredictable toxins

they may increase the risk of allergenic reaction

 

 

Genetically Modified Foods:

Are They a Risk to Human/Animal Health?

By Arpad Pusztai, Ph.D.

 

Information is scarce about health hazards, such as toxicity in

genetically modified (GM) crops.

 

Scarcity of safety tests

 

How can the public make informed decisions about genetically

modified (GM) foods when there is so little information about its

safety? The lack of data is due to a number of reasons, including:

 

It's more difficult to evaluate the safety of crop-derived foods

than

individual chemical, drug, or food additives. Crop foods are more

complex and their composition varies according to differences in

growth and agronomic conditions.

 

Publications on GM food toxicity are scarce. An article in Science

magazine said it all: " Health Risks of Genetically Modified Foods:

Many Opinions but Few Data " .

In fact, no peer-reviewed publications of clinical studies on the

human health effects of GM food exist. Even

animal studies are few and far between.

 

The preferred approach of the industry has been to use compositional

comparisons between GM and non-GM crops. When they are not

significantly different the two are regarded as " substantially

equivalent " , and therefore the GM food crop is regarded as safe as

its conventional counterpart.

This ensures that GM crops can be patented without animal

testing.

 

However, substantial equivalence is an unscientific concept

that has never been properly defined and there are no legally

binding rules on how to establish it.2

 

GM foods may cause bacteria to become resistant to antibiotics.

They can also produce allergies.

When food-crops are genetically modified, ( " genetically modified "

food is a misnomer!)

 

one or more genes are incorporated into the crop's

genome using a vector containing several other genes, including as a

minimum, viral promoters, transcription terminators, antibiotic

resistance marker genes and reporter genes. Data on the safety of

these are scarce even though they can affect the safety of the GM

crop.

 

For example:

 

DNA does not always fully break down in the alimentary tract.

 

Gut bacteria can take up genes and GM plasmids5 and this opens up

the possibility of the spread of antibiotic resistance.

 

Insertion of genes into the genome can also result in unintended

effects, which need to be reduced/eliminated by selection, since

some of the ways the inserted genes express themselves in the host

or the way they affect the functioning of the crop's own genes are

unpredictable.

 

This may lead to the development of unknown toxic/allergenic

components, which we cannot analyze for and seriously limiting the

selection criteria.

 

Current testing methods need radical improvements.

 

Currently, toxicity in food is tested by chemical analysis of

macro/micro nutrients and known toxins. To rely solely on this

method is at best inadequate and, at worst, dangerous.

 

Better diagnostic methods are needed, such as mRNA fingerprinting,

proteomics and secondary metabolite profiling.6 However, consuming

even minor constituents with high biological activity may have major

effects on the gut and body's metabolism, which can only be revealed

from animal studies. Thus novel

toxicological/nutritional methods are urgently needed to screen for

harmful consequences on human/animal health and to pinpoint these

before allowing a GM crop into the food chain.

 

Safety tests on commercial GM crops

 

GM tomatoes: The first and only safety evaluation of a GM crop, the

FLAVR SAVRTM tomato, was commissioned by Calgene, as required by the

FDA. This GM tomato was produced by inserting kanr genes into a

tomato

by an 'antisense' GM method. The test has not been peer-reviewed or

published but is on the internet.

 

The results claim there were no significant alterations in total

protein, vitamins and mineral contents

and in toxic glycoalkaloids. Therefore, the GM and parent tomatoes

were deemed to be " substantially equivalent. "

 

Some rats died within a few weeks after eating GM tomatoes.

 

In acute toxicity studies with male/female rats, which were tube-fed

homogenized GM tomatoes, toxic effects were claimed to be absent. In

addition, it was concluded that mean body and organ weights, weight

gains, food consumption and clinical chemistry or blood parameters

were not significantly different between GM-fed and control groups.

 

However:

The unacceptably wide range of rat starting weights (±18% to ±23%)

invalidated these findings.

 

No histology on the intestines was done even though stomach sections

showed mild/moderate erosive/necrotic lesions in up to seven out of

twenty female rats but none in the controls.

 

However, these were considered to be of no importance, although in

humans they could lead to

life-endangering hemorrhage, particularly in the elderly who use

aspirin to prevent thrombosis.

 

Seven out of forty rats on GM tomatoes died within two weeks for

unstated reasons.

 

These studies were poorly designed and therefore the conclusion that

FLAVR SAVRTM tomatoes were safe does not rest on good science,

questioning the validity of the FDA's decision that no toxicological

testing of other GM foods will in future be required.

 

Rats' ability to digest was decreased after eating GM corn.

 

GM maize: Two lines of Chardon LL herbicide-resistant GM maize

expressing the gene of Phosphinothricin Acetyltransferase Enzyme

(PAT-PROTEIN) before and after ensiling showed significant

differences in fat and carbohydrate contents compared with non-GM

maize and were therefore substantially different.

 

Toxicity tests were only performed with the PAT-PROTEIN even though

with this the unpredictable effects of the gene transfer or the

vector or gene insertion could not be demonstrated or excluded.

 

The design of these experiments was also flawed because:

The starting weight of the rats varied by more than ± 20% and

individual feed intakes were not monitored.

Feed conversion efficiency on PAT-PROTEIN was significantly reduced.

Urine output increased and several clinical parameters were also

different.

The weight and histology of the digestive tract (and pancreas) was

not measured.

 

Thus, GM maize expressing PAT-PROTEIN may present unacceptable

health risks.

 

Allergen content increased when soybeans were genetically modified.

Compositional studies

 

GM soybeans: To make soybeans herbicide resistant, the gene of

5-enolpyruvylshikimate-3-phosphate synthase from Agrobacterium was

used.

Safety tests claim the GM variety to be " substantially equivalent "

to conventional soybeans.10 The same was claimed for GTS

(glyphosate-resistant soybeans) sprayed with this herbicide.

 

However, several significant differences between the GM and control

lines were recorded and the statistical method used was flawed

because:

Instead of comparing the amounts of components in a large number of

samples of each individual GTS with its appropriate parent line

grown side-by-side and harvested at the same time, the authors

compared samples from different locations and harvest times.

 

There were also differences in the contents of natural isoflavones

(genistein, etc.) with potential importance for health.

 

Additionally, the trypsin inhibitor (a major allergen) content was

significantly increased in GTS.

Because of this, and the large variability (± 10% or more), the

lines could not be regarded as " substantially equivalent. "

 

GM potatoes: There is only one peer-reviewed publication on GM

potatoes that express the soybean glycinin gene.

However, the expression level was very low and no improvements in

the protein content or amino acid profile were obtained.

 

The toxin level of GM cotton is unpredictable.

 

GM rice: The kind that expresses soybean glycinin gene (40-50 mg

glycinin/g protein) has been developed14 and is claimed to contain

20% more protein. However, the increased protein content was

probably due to a decrease in moisture rather than true increase in

protein putting a question mark over the significance of this GM

crop.

 

GM cotton: Several lines of GM cotton plants have been developed

using a gene from Bacillus thuringiensis subsp. kurstaki providing

increased

protection against major lepidopteran pests. The lines were claimed

to be " substantially equivalent " to parent lines15 in levels of

macronutrients and gossypol, cyclopropenoid fatty acids and

aflatoxin levels were less than those in conventional seeds.

However, because of

the use of inappropriate statistics it is questionable whether the

GM and non-GM lines were truly equivalent, particularly as

environmental stresses could have unpredictable effects on

antinutrient/toxin levels.16

 

Nutritional/toxicological studies

 

Herbicide-resistant soybean: Studies have been conducted on the

feeding

value17 and possible toxicity18 for rats, broiler chickens, catfish

and dairy cows of two GM lines of glyphosate-resistant soybean

(GTS). The growth, feed conversion efficiency, catfish fillet

composition, broiler

breast muscle and fat pad weights and milk production, rumen

fermentation and digestibilities in cows were claimed to be similar

for GTS and non-GTS.

 

However:

These experiments were poorly designed since the high dietary

protein concentration and the low inclusion level of GTS could have

masked any GM effect.

 

No individual feed intakes, body or organ weights were given and no

histology was performed, except some qualitative microscopy on the

pancreas.

The feeding value of the two GTS lines was not substantially

equivalent either because the rats grew significantly better on one

of the GTS lines than on the other.

 

The experiment with broiler chicken was a commercial and not a

scientific study.

 

The catfish experiment showed again that the feeding value of one of

the GTS lines was superior to the other.

Milk production and performance of lactating cows also showed

significant differences between cows fed GM and non-GM feeds.

Moreover, testing of the safety of 5-enolpyruvylshikimate-3-

phosphate synthase which renders soybeans glyphosate-resistant18 was

irrelevant

because in the gavage studies an E. coli recombinant and not the GTS

product was used. Their effects could be different as the

differences in

post-translational modification could have impaired their stability

to gut proteolysis.

 

Thus, the claim that the feeding value of GTS and non-GTS lines was

substantially equivalent is at best premature.

 

Rats had meager weight gain when fed GM soybeans.

 

 

 

 

 

In a separate study19 it was claimed that rats and mice which were

fed 30% toasted GTS or non-GTS in their diet had no significant

differences in nutritional performance, organ weights,

histopathology and production of IgE and IgG antibodies. However,

under the unphysiological -- basically, starvation -- conditions of

these experiments when, instead

of the normal daily growth of 5-8 g per day, the rats grew less than

0.3 g and mice not at all, no valid conclusions could be drawn.

GM corn:

 

One broiler chicken feeding study with rations containing

transgenic Event 176 derived Bt corn (Novartis) has been

published.20

However, the results of this trial are more relevant to commercial

than academic scientific studies.

 

GM peas seem to have no harmful effects on animals but that doesn't

mean they are safe for humans.

 

GM peas: The nutritional value of diets containing GM peas

expressing bean alpha-amylase inhibitor when fed to rats for 10 days

at two different (30% or 65%) dietary inclusions, was shown to be

similar to that of parent-line peas.21

 

Even at 65% level the difference was small mainly because the

alpha-amylase inhibitor expressed in the peas was quickly digested

in the rat gut and its antinutritive effect abolished. Unfortunately

no gut histology was done or lymphocyte responsiveness measured.

Although some organ weights, mainly the caecum and pancreas were

different, those of others were remarkably similar suggesting that

GM

peas may be used in the diets of farm animals at low/moderate levels

if their progress was carefully monitored.

However, to establish its safety for humans a more rigorous specific

risk assessment will have to be carried out with several GM lines.

This should include:

 

An initial nutritional/toxicological testing on laboratory animals

If no harmful effects are then detected, it should be followed by

clinical, double-blind, placebo-type tests with human volunteers,

keeping in mind that any possible harmful effects would be

particularly serious with the young, old, and disabled.

 

A protocol for such testing was given at the OECD conference in

Edinburgh, February 2000 and subsequently published.22

 

Toxins were found in mice after eating GM potatoes.

 

GM potatoes: In a short feeding study to establish the safety of GM

potatoes expressing the soybean glycinin gene, rats were daily force-

fed with 2 g of GM or control potatoes/kg body weight.23 Although no

differences in growth, feed intake, blood cell count and composition

and organ weights between the groups was found, the potato intake of

the animals was too low and unclear, whether the potatoes were raw

or boiled.

 

Feeding mice with potatoes transformed with a Bacillus thuringiensis

var. kurstaki Cry1 toxin gene or the toxin itself was shown24 to

have caused villus epithelial cell hypertrophy and multinucleation,

disrupted microvilli, mitochondrial degeneration, increased numbers

of lysosomes and autophagic vacuoles and activation of crypt Paneth

cells. The

results showed that despite claims to the contrary, CryI toxin was

stable in the mouse gut and therefore GM crops expressing it need to

be subjected to " thorough tests...to avoid the risks before

marketing.24

When the health risks of GM potatoes were revealed in some studies,

a debate ensued.

 

 

In another study, young, growing rats were pair-fed on iso-proteinic

and iso-caloric balanced diets containing raw or boiled non-GM

potatoes and GM potatoes with the snowdrop (Galanthus nivalis) bulb

lectin (GNA) gene.

 

The results showed that the mucosal thickness of the stomach and

the crypt length of the intestines of rats fed GM potatoes was

significantly increased.

 

Most of these effects were due to the insertion

of the construct and not to GNA which had been been pre-selected as

a non-mitotic lectin unable to induce hyperplastic intestinal

growth26 and epithelial T lymphocyte infiltration.

 

Although there is controversy

about the tests, most of the adverse comments on this Lancet paper

were personal, non-peer reviewed opinions and, as such, of limited

scientific value. The findings, on the other hand, were published in

a peer-reviewed publication25 and the criticism replied to.7 The

work, however, has not been repeated nor results contradicted and it

is therefore imperative that the effects on the gut structure and

metabolism of all other GM crops developed using similar techniques

and

genetic vectors should be thoroughly investigated before their

release into the food chain.

 

GM tomatoes: This study with a GM tomato expressing B. thuringiensis

toxin CRYIA(b) gene was published in a book and not in a peer-

reviewed

journal. However, its importance was underlined by the

immunocytochemical demonstration of in vitro binding of Bt toxin to

the caecum/colon from humans and rhesus monkeys.27 Although in vivo

the Bt toxin was not bound by the rat gut, this was possibly due to

the authors' use of recombinant Bt toxin.

 

Allergies are a major concern with GM food, especially if

ingredients are not labeled in packaged food.

 

Allergenicity studies

 

One of the major health concerns with GM food is its potential to

increase allergies and anaphylaxis in humans eating unlabeled GM

foodstuffs.

When the gene is from a crop of known allergenicity, it is easy to

establish whether the GM food is allergenic using in vitro tests,

such

as RAST or immunoblotting, with sera from individuals sensitised to

the original crop. This was demonstrated in GM soybeans expressing

the brasil nut 2 S protein28 or in GM potatoes expressing cod

protein genes.

 

It is also relatively easy to assess whether genetic engineering

affected the potency of endogenous allergens.30 Some farm workers

exposed to B. thuringiensis pesticide were shown to have developed

skin

sensitization and IgE antibodies to the Bt spore extract. With their

sera it may now therefore be possible to test for the allergenic

potential of GM crops expressing Bt toxin.31 It is all the more

important because Bt toxin Cry1Ac has recently been shown to be a

potent oral/nasal antigen and adjuvant.32

 

There are no reliable ways to test GM foods for allergies.

 

Assessment of the allergenicity of a GM foodcrop, however, is

difficult

when the gene is transferred from a source not eaten before or with

unknown allergenicity or on gene transfer/insertion a new allergen

or adjuvant is developed or the expression of a minor allergen is

increased. Unfortunately, while there are good animal models for

nutritional/toxicological testing, no such models exist for

allergenicity testing.

Presently only indirect and rather scientifically unsound methods,

such as finding SHORT sequence homologies (at least 8 contiguous

amino acids) to any of the about 200 known allergens, are used for

the assessment of allergenicity.

 

The decision-tree type of indirect approach based on factors (such

as

size and stability) of the transgenically expressed protein33 is

even more unsound, particularly as its stability to gut proteolysis

is

assessed by an in vitro (simulated) testing34 instead of in vivo

(human/animal) testing and this is fundamentally wrong. The concept

that most allergens are abundant proteins is also misleading because

for

example Gad c 1, the major allergen in codfish, is not a predominant

protein.29

 

However, when the gene responsible for the allergenicity is known,

such as the gene of the alpha-amylase/trypsin inhibitors/allergens

in rice, cloning and sequencing opens the way for reducing their

level by antisense RNA strategy.35

 

Thus, in the absence of reliable methods for allergenicity testing,

it is at present impossible to definitely establish whether a new GM

crop is allergenic or not before its release into the human/animal

food/feed chain.

 

We need more and better testing methods before making GM foods

available for human consumption.

 

In conclusion

 

One has to agree with the piece in Science1 that there are many

opinions

but scarce data on the potential health risks of GM food crops, even

though these should have been tested for and eliminated before their

introduction. Our present data base is woefully inadequate.

Moreover, the scientific quality of what has been published is, in

most instances not up to expected standards. If, as claimed, our

future is dependent on the success of the promise of genetic

modification delivering wholesome, plentiful, more nutritious and

 

safe GM foods, the inescapable conclusion

of this review is that the present crude method of genetic

modification

has so far not delivered these benefits and the promise of a

superior second generation is still in the future. Although it is

argued by some that small differences between GM and non-GM crops

have little

biological meaning, it is clear that most GM and parental line crops

fall short of the definition of " substantial equivalence. " In any

case,

this crude, poorly defined and unscientific concept outlived its

possible previous usefulness and we need novel methods and concepts

to

probe into the compositional, nutritional/toxicological and

metabolic

differences between GM and conventional crops and into the safety of

the

genetic techniques used in developing GM crops if we want to put

this

technology on a proper scientific foundation and allay the fears of

the general public. We need more science, not less.6,7

 

 

BioScience Productions, Inc., an organization promoting

bioscience literacy. Educators have permission to reprint articles

for classroom use; other users, please contact editor for reprint

permission. See reprint policy.

 

About the author: Arpad Pusztai, Ph.D., received his degree in

Chemistry in Budapest, Hungary and his B.Sc. in Physiology and Ph.D.

in

Biochemistry at the University of London in England. Over his nearly

50-year career, he worked at universities and research institutes in

Budapest; London; Chicago, U.S.; and Aberdeen, Scotland (Rowett

Research Institute).

 

He has published close to 300 primary peer-reviewed papers and

wrote or edited 12 scientific books. In the last 30 years he

pioneered research into the effects of dietary lectins

(carbohydrate-reactive proteins), including those transgenically

expressed in GM crop plants, on the gastrointestinal tract. Since

his

contract was not renewed with Rowett as a result of disagreements,

 

Dr. Pusztai has been lecturing on his GM potato research all over

the world and acting as a consultant to groups starting up research

into the health effects of GM food.

http://www.freenetpages.co.uk/hp/a.pusztai/

 

Genetically Modified Foods:

Are They a Risk to Human/Animal Health?

 

The Ecological Impacts of Agricultural Biotechnology

Dr. Miguel Altieri presents an analysis of the damaging effects of

GM crops on our environment in an article on this site.

http://www.actionbioscience.org/biotech/altieri.html

 

GM food quiz

How much do you know about GM food? Take this online quiz created by

the Environmental News Network.

 

http://www.enn.com/features/2000/09/09062000/gmfood_30998.asp

Food for our future

This U.K. Food Future site explains GM crops and foods, examining

both benefits and concerns. Also features a glossary of GM food

terms.

http://www.foodfuture.org.uk/

 

Alliance for Bio-integrity

The executive director of this organization explains " Why concerns

about health risks of genetically engineered food are scientifically

justified. "

http://www.biointegrity.org/health-risks/health-risks-ge-foods.htm

 

How are genes engineered?

Using a minimum of technical terms, this brief how-to explains how

genes are manipulated in genetic engineering.

http://www.psrast.org/whisge.htm

 

Transgenic (GM) crops on the market

 

Colorado State University provides a descriptive list of transgenic

crops in the U.S. and other parts of the world. The second link

takes you to their home page where you will find other menu options

and resources.

http://www.colostate.edu/programs/lifesciences/TransgenicCrops/curren

t.html

 

http://www.colostate.edu/programs/lifesciences/TransgenicCrops/index.

html

 

 

Myths about GE food

New Zealand's Consumers for Education about Genetic Engineering has

prepared this helpful guide to debunk misconceptions about genetic

engineering.

http://www.prorev.com/genetic.htm

 

More on Dr. Pusztai's work

A web page run by Dr. Pusztai's colleague, Dr. Thorkild of the

University of Copenhagen, is devoted to an examination of Dr.

Pusztai's research and other GMO information.

http://plab.ku.dk/tcbh/Pusztaitcbh.htm

 

Biotechnology resources

Biotechnology-related news, books and web resources.

http://www.n-e-x-u-s.com/biotechnology/

 

Campaign to label genetically modified food

If you believe that food products should contain GM information on

labels, join this campaign which provides an opportunity for you to

send letters to US congress, government agencies, grocery stores and

food manufacturers as well as to send emails to the media about your

views on the issue.

http://www.thecampaign.org/

 

Center for Food Safety campaigns

If you oppose the FDA's regulations on genetically modified food,

take action through this site.

http://www.foodsafetynow.org/

 

True Food Network

This network is a free service from Greenpeace to connect consumers

who

want to take action to end the use of genetically engineered (GE)

ingredients in our foods.

http://www.truefoodnow.org/

 

Campaign to ban genetically modified food

The Natural Law Party of the UK invites you to join their campaign

against GMOs.

http://www.btinternet.com/~nlpwessex/Documents/gmocarto.htm

 

Copy gene - genetic material that contains the genetic code for a

desirable trait which has been copied from the DNA of the donor to

transfer to the host organism. (Currently, it is not technically

possible to take a gene from a donor organism and insert it directly

into the host organism).

DNA - Deoxyribonucleic acid, the fundamental genetic material of all

cells, that acts as the carrier of genetic information.

 

Gene - the biological unit of inheritance, which transmits

hereditary information of a physical, behavioral, or biochemical

trait.

 

Genetic modification - a technique for copying and transferring

individual genes to another living organism to alter its genetic

make up, thereby incorporating or deleting specific characteristics

into or from the organism.

 

Toxin - a poison, usually originating in a plant or microorganism.

 

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Many

opinions but few data. Science 288, 1748-1749.

2) Millstone, E., Brunner, E. and Mayer, S. (1999) Beyond

substantial

equivalence. Nature 401, 525-526.

3) Schubbert, R., Lettmann, C. and Doerfler, W. (1994) Ingested

foreign

(phage M13) DNA survives transiently in the gastrointestinal tract

and

enters the blood stream of mice. Molecules, Genes and Genetics 242,

495-504.

4) Schubbert, R. Hohlweg, U., Renz, D. and Doerfler, W. (1998) On

the

fate of orally ingested foreign DNA in mice: chromosomal association

and

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Harvey, P., Patzer, S. and Fuchs, R.L. (1996) The composition of

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Actionbioscience.org original lesson

This lesson has been written by a science educator to specifically

accompany the above article. It includes article content and

extension questions, as well as activity handouts for different

grade levels.

 

Lesson Title: GM Foods: Are They Safe?

Levels: high school - undergraduate

Summary: This lesson examines potential benefits and risks of

genetically modified foods. Students can interview a biotech

company, design enhanced GM food products or packaging labels, form

a GM food lobby group… and more!

http://www.actionbioscience.org/lessonaccess/pusztai.html

 

Lessons for middle school

This article is too advanced to be used as the basis for middle

school lessons, so no links to external lessons are provided.

 

Useful links for student research

In addition to the links in the " learn more " section above:

» Genetic Engineering Glossary

The International Forum for Genetic Engineering provides an online

glossary of terms for genetics and genetic engineering.

http://www.anth.org/ifgene/glossary.htm

 

» Genetically-Modified Crops Glossary

The European Commission provides a brief glossary of terms related

to GM crops that may be useful to student research.

http://europa.eu.int/comm/agriculture/publi/gmo/glossary.htm

 

» FDA (Food and Drug Administration) USA

Main U.S. government agency responsible for safety of GM foods to

consumers. Has many links to pages and articles, press releases,

links on a variety of aspects of food safety.

http://www.fda.gov/

» American Society of Plant Biologists (ASPB)

Includes a book collection of " Editor's Choice " articles devoted to

biotechnology and genetically modified crops. The articles are

online or the book can be ordered.

www.aspb.org

» The National Center for Biotechnology

This organization in the U.K. has extensive information about GMOs

and biotechnology.

 

http://www.ncbe.reading.ac.uk/NCBE/GMFOOD/menu.html