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The Debate Over Genetically Modified Foods

Kerryn Sakko


Before their release, (GM) foods require more encompassing tests to assess their:

  • effect on human health
  • impact on the environment
  • overall benefits or risks to society

May 2002


Can strawberry crops be genetically engineered to survive frost? Photo by Ken Hammond.

Food can be engineered to prevent disease.
  • Rice with built-in Vitamin A that can help prevent blindness in 100 million children suffering from Vitamin A deficiency;
  • A tomato that softens more slowly, allowing it to develop longer on the vine and keep longer on the shelf;
  • Potatoes that absorb less fat when fried, changing the ever-popular french fries from junk food into a more nutritional food;
  • Strawberry crops that can survive frost;
  • An apple with a vaccine against a virus that causes childhood pneumonia.

These are some of the benefits promised by biotechnology. The debate over its benefits and safety, however, continues. Do we really need to fear mutant weeds, killer tomatoes, and giant corn and will the benefits be delivered?

Conventional breeding is a slow, unpredictable process.
Desired GM organisms can be bred in one generation.

Conventional Breeding versus Genetically Modified (GM) Crops

For thousands of years farmers have used a process of selection and cross breeding to continually improve the quality of crops. Even in nature, plants and animals selectively breed, thus ensuring the optimum gene pool for future generations. Traditional breeding methods are slow, requiring intensive labor: while trying to get a desirable trait in a bred species, undesirable traits will appear and breeders must continue the process over and over again until all the undesirables are bred out.

In contrast, organisms acquire one specific gene or a few genes together through genetic modification, without other traits included and within a single generation. However, this technology too is inherently unpredictable and some scientists believe it can produce potentially dangerous results unless better testing methods are developed.

The Fallacy of Equating Gene-Splicing With Traditional Breeding: Traditional breeding is based on sexual reproduction between like organisms. The transferred genes are similar to genes in the cell they join. They are conveyed in complete groups and in a fixed sequence that harmonizes with the sequence of genes in the partner cell. In contrast, bioengineers isolate a gene from one type of organism and splice it haphazardly into the DNA of a dissimilar species, disrupting its natural sequence. Further, because the transplanted gene is foreign to its new surroundings, it cannot adequately function without a big artificial boost.

Biotechnicians achieve this unnatural boosting by taking the section of DNA that promotes gene expression in a pathogenic virus and fusing it to the gene prior to insertion. The viral booster (called a “promoter”) radically alters the behavior of the transplanted gene and causes it to function in important respects like an invading virus — deeply different from the way it behaves within its native organism and from the way the engineered organism’s own genes behave. …
Consequently, not only does the foreign gene produce a substance that has never been in that species, it produces it in an essentially unregulated manner that is uncoordinated with the needs and natural functions of the organism.”11

Even genes from bacteria can be used to engineer crops.

One of the main differences between conventional and genetically modified crops is that the former involves crosses either within species or between very closely related species. GM crops can have genes either from closely related species or from distant species, even bacteria and viruses. A typical example of a GM crop in the market in Australia is cotton known as Ingard.6 This cotton has a gene from a naturally occurring soil bacterium known as Bacillus thuringiensis (Bt). The Bt gene renders the cotton resistant to the heliothis caterpillar, a major threat to the cotton industry. In this example, an appropriate and selected gene (in a construct containing a promoter, transcription terminator, selection marker, etc. genes) was inserted into the cotton, unlike in conventional breeding where not only the appropriate gene was inherited in breeding but other genes as well.10

60% of U.S. grocery food contains GM ingredients.

When combining two crops using standard agricultural techniques, genes are allowed to mix at random. A typical example is Triticale, a synthetic hybrid between wheat and rye grown in Europe, which is the result of combining 50,000 largely untested genes, 25,000 from each species.10 GM crops, in contrast, have specific genes inserted to produce the same desired effect.

Biotech plants are now grown on about 130 million acres in 13 countries, including Argentina, Canada, and Germany. In 2001, 3.6 million acres were used for GM crops in the U.S. More than 60% of all processed foods in the U.S. contain ingredients from GM soybeans, corn, or canola.1

Benefits: one side of the debate

Growing GM crops is initially costly but cheaper in the long run.

GM supporters tell farmers that they stand to reap enormous profits from growing GM crops. Initially, the cost is expensive but money is saved on pesticides. To produce the GM crops, modern biotechnology is used which requires highly skilled people and sophisticated and expensive equipment.7 Large companies need considerable investments in laboratories, equipment and human resources, hence the reason why GM crops are more expensive for farmers than traditional crops. GM crops, farmers are told, are a far better option. It takes a shorter time to produce the desired product, it is precise and there are no unwanted genes.

Farmers need less herbicides in GM fields.

Herbicide-resistant crops
So what other advantages do GM crops hold for farmers? GM crops can be produced to be herbicide resistant. This means that farmers could spray these crops with herbicide and kill the weeds, without affecting the crop. In effect, the amount of herbicide used in one season would be reduced, with a subsequent reduction in costs for farmers and consumers. For Ingard cotton, pest resistance was built into the cotton, hence reducing and even removing the use of pesticides, which are not only expensive but, more importantly, harmful to the environment.

Biotechnology companies are even experimenting with crops that can be genetically modified to be drought and salt-tolerant, or less reliant on fertilizer, opening up new areas to be farmed and leading to increased productivity. However, the claims of less herbicide usage with GM crops have till now not been independently supported by facts.

Better quality foods
Even animals can be genetically modified to be leaner, grow faster, and need less food. They could be modified to have special characteristics, such as greater milk production in cows. These modifications again lead to improved productivity for farmers and ultimately lower costs for the consumer. Modified crops could perhaps prevent outbreaks such as foot and mouth disease, which has devastated many farmers and local economies.

No safety studies have been done on GM salmon.

No such products have been released to date; however, some are under consideration for release. For example, GM salmon, capable of growing almost 30 times faster than natural salmon, may soon be approved by the FDA (Food and Drug Administration) in the U.S. for release into open waters without a single study on the impact on human health or the environment.5

The following are some examples of food plants that are undergoing field trials:10

  • apples that resist insect attack
  • bananas free of viruses and worm parasites
  • coffee with a lower caffeine content
  • cabbage that resists caterpillar attacks
  • melons that have a longer shelf life
  • sunflowers that produce oil with lower saturated fat

Risks: the other side of the debate

The major concerns of those who oppose GM foods center on the:

  • potential danger to the environment
  • possible health risks to humans

Environmental damage
The problem with GM crops is that there is little known about what effect they will have in, say, 20 years time. The genetic structure of any living organism is complex and GM crop tests focus on short-term effects. Not all the effects of introducing a foreign gene into the intricate genetic structure of an organism are tested. Will the pests that a crop was created to resist eventually become resistant to this crop?

Will herbicide resistance pass on to weeds?

Then there is always the possibility that we may not be able to destroy GM crops once they spread into the environment. In Europe, for example, a strain of sugar beet that was genetically modified to be resistant to a particular herbicide has inadvertently acquired the genes to resist another.7 This was discovered when farmers attempted to destroy the crop in Britain, France and the Netherlands, where it was being tested, and 0.5% of the crop survived.7 More noxious herbicides had to be used to remove the remainder of the plantation. What if this herbicide resistance passed on to weeds?

The Skylark and the Monarch butterfly were affected by GM crops.

Risk to food web
A further complication is that the pesticide produced in the crop may unintentionally harm creatures. In Britain, a native farm bird, the Skylark, was indirectly affected by the introduction of GM sugar beets designed to resist herbicides. In planting this crop, the weeds were reduced substantially. However, since the birds rely on the seeds of this weed in autumn and winter, researchers expect that up to 80% of the Skylark population would have to find other means of finding food.4

GM crops may also pose a health risk to native animals that eat them. The animals may be poisoned by the built-in pesticides. Tests in the U.S. showed that 44% of caterpillars of the monarch butterfly died when fed large amounts of pollen from GM corn.8

Will genes from GM plants transfer to other organisms?

Cross-pollination is a concern for both GM crops and conventional breeding, especially with the more serious weeds that are closely related to the crops. With careful management this may be avoided. For example, there is a type of maize that will not breed with other strains and scientists are hoping that it could help to prevent cross-pollination.3 Genetic modification to herbicide resistant crops could insert the gene that prevents the problem. The number of herbicide-tolerant weeds has increased over the years from a single report in 1978 to the 188 herbicide-tolerant weed types in 42 countries reported in 1997.6 They are an ever-increasing problem and genetic engineering promises to stop it. But will genes from GM plants spread to other plants, creating superweeds and superbugs we won’t be able to control?

The taco scandal in the U.S. heightened awareness of GM risks.

GM mix-ups
Humans can inadvertently eat foods that contain GM products meant as animal feed, i.e., crops modified for increased productivity in animals. This happened in the U.S., where traces of a StarLink GM crop, restricted for use only in feed, were found in taco shells.2 Apparently no one became ill but other such occurrences may lead to health problems.

Will GM food increase the problems with resistance to antibiotics?

Another concern is disease. Since some crops are modified using the DNA from viruses and bacteria, will we see new diseases emerge? What about the GM crops that have antibiotic-resistant marker genes? Marker genes are used by scientists to determine whether their genetic modification of a plant was successful. Will these antibiotic-resistant genes be transferred to microorganisms that cause disease? We already have a problem with ineffective antibiotics. How can we develop new drugs to fight these new bugs?


Proponents of GM crops claim that advantages may be many, such as:

Conclusion: Further studies are needed to assess the potential risks of GM foods even though the technology promises many benefits.
  • improved storage and nutritional quality
  • pest and disease resistance
  • selective herbicide tolerance
  • tolerance of water, temperature and saline extremes
  • improved animal welfare
  • higher yields and quality

However, until further studies can show that GM foods and crops do not pose serious threats to human health or the world’s ecosystems, the debate over their release will continue. Living organisms are complex and tampering with their genes may have unintended effects. It is in our common interest to support concerned scientists and organizations, such as Friends of the Earth who demand “mandatory labeling of these food products, independent testing for safety and environmental impacts, and liability for harm to be assumed by biotech companies.”5

Kerryn Sakko is an undergraduate student at Adelaide University, Australia, studying for a double degree in chemical engineering, mathematics and computer science. In 2001, she represented Australia, with 19 other students from around the country, at the APEC Youth Science Forum held in Singapore. Currently, Kerryn assists the Junior Field Naturalist Club and helps in the supervision and running of events for CSIRO’s Double Helix Science Club. She is also a member of Youth Science Forum, a club that promotes science, where she contributes her time and skills to science learning events, including Sieman’s Science School.

The Debate Over Genetically Modified Foods

Ag BioTech InfoNet

Ag BioTech InfoNet covers all aspects of the application of biotechnology and genetic engineering in agricultural production, food processing, and marketing.

GM food information

The National Center for Biotechnology Information, maintained by the University of Reading, UK, provides many reading choices on the subject of GM food as it relates to the United Kingdom.

USDA Agricultural Biotechnology: Questions and Answers

Breeders have been evaluating new products developed through agricultural biotechnology for centuries. In addition to these efforts, the United States Department of Agriculture (USDA), the Environmental Protection Agency (EPA), and the Food and Drug Administration (FDA) work to ensure that crops produced through genetic engineering for commercial use are properly tested and studied to make sure they pose no significant risk to consumers or the environment. Learn the answers to popular AG Biotech questions, as well as gain access to useful resources, including a biotechnology glossary.

Biotechnology resources

Biotechnology-related news, books and web resources.

Food and Environment Electronic Digest (FEED)

FEED is a free email newsletter that will keep you informed about food production and safety issues.


Teaching Resources from the Northwest Association for Biomedical Research (NWABR)

The Northwest Association for Biomedical Research (NWABR) strengthens public trust in research through education and dialogue. Its diverse membership spans academic, industry, non-profit research institutes, health care, and voluntary health organizations. Through membership and extensive education programs, it fosters a shared commitment to the ethical conduct of research and ensures the vitality of the life sciences community.

Consumer Awareness
This four lesson curriculum engages middle and high school students in an investigation of personal care products. Being an informed consumer requires critical evaluation skills and a basic understanding of science and regulations. original lesson

This lesson has been written by a science educator to specifically accompany another article about GM food on this site. Educators can delete the section on article content and extension questions but may want to use the activity handouts to support the article above.

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!

Download/view lesson.
(To open the lesson’s PDF file, you need Adobe Acrobat Reader free software.)

Environmental Inquiry

Cornell University offers background information and classroom activities, including lab work using bioassays, to examine toxicology.


Understanding Science