Genetic modification employs recombinant deoxyribonucleic acid (rDNA) technology to alter the genes of microorganisms, plants, and animals. Genetic modification is also called biotechnology, gene splicing, recombinant DNA technology, or genetic engineering. Contemporary genetic modification was developed in the 1970s and essentially transfers genetic material from one organism to another. The modification of organisms has existed for centuries in the form of plant-breeding techniques (such as cross-fertilization) used to produce desired traits. With genetic modification, however, isolated genes are inserted into plants for a desired trait with a much quicker result than occurs when cross-breeding plants, which can take years. These isolated genes do not have to come from similar species in order to be functional; theoretically, genes can be transferred among all microorganisms, plants, and animals.
Examples of Genetically Modified Foods
Crops may be modified to increase resistance to pests and disease, increase adaptability to environmental conditions, improve flavor or nutritional profile, delay ripening, or increase shelf life. Many common crops are genetically modified, such as corn, canola, flax, potatoes, tomatoes, squash, and soybeans. Corn and potatoes may be modified with a gene to produce an endotoxin that protects them against the corn-borer pest and the potato beetle, respectively. A soybean can be genetically modified with a gene from a bacterium to make it herbicide resistant. By inserting two genes from daffodil and one gene from a bacterium, rice can be enriched with beta-carotene.
In the early 1990s, genetically modified tomatoes (Flavr Savr by Calgene, Inc.) were deemed safe by the U.S., Canadian, and British governments and introduced into the market. These tomatoes were bred to stay firm after harvest so they could remain on the vine longer and ripen to full flavor. However, the tomatoes were so delicate that they were difficult to transport without damage, and the product was pulled from the market in 1997.
Recombinant bovine growth hormone (rBGH), also known as recombinant bovine somatotropin (rBST), is another example of a product that has not been very successful. Recombinant BGH (Posilac by Monsanto Company) is a genetically engineered version of a growth hormone that increases milk output in dairy cows by as much as 10 to 30 percent. In 1999 the United Nations Food Safety Agency unanimously declared the use of rBGH unsafe after confirming reports of excess levels of the naturally occurring insulin-like growth factor one (IGF-1), including its highly potent variants, in rBGH milk and concluding that these posed major risks of cancer. Health Canada also banned the use of rBGH in milk production in 1999, but the hormone is still permitted in the U.S. milk supply.
Safety of Genetically Modified Foods
Biotechnology has moved at such a rapid pace that the safety of genetically modified foods has become a concern. At this time, there are no long-term, large-scale tests to prove their safety—or lack thereof. Unforeseen consequences may arise from widespread genetic modification of the food supply, including:
- •Allergic reaction. If a gene producing a protein that causes an allergic reaction is engineered into corn, for example, an individual who is allergic to that protein may experience an allergic reaction to the corn. Despite the fact that food-regulating agencies require companies to report whether altered food contains any suspect proteins, unknown allergens could potentially slip through the system.
- Increased toxicity. Genetic modification may enhance natural plant toxins in unexpected ways. When a gene is switched on, besides having the desired effect, it may also stimulate the production of natural toxins.
- Resistance to antibiotics. As part of the genetic modification of organisms, marker genes are used to determine if the desired gene has been successfully embedded. Marker genes typically provide resistance to antibiotics. Even though marker genes are genetically scrambled before use to reduce the potential for this danger, their use could contribute to the growing problem of antibiotic resistance.
- Herbicide-resistant weeds. Once modified crops are planted, genes may travel via airborne, waterborne, or animal-borne seeds and pollen to weedy relatives, creating "superweeds" that are able to resist herbicides.
- Harm to other organisms. Nontargeted species may inadvertently be harmed by a genetically modified plant producing endotoxins intended for a specific pest. For example, nearly all insect-resistant plants contain a gene from the bacterium Baciullus thuringiensis (Bt), which results in the production of a natural endotoxin that is toxic to all insects. The Bt endotoxin is widely used by organic and conventional farmers because it is a relatively harmless, natural pesticide. However, genetically modified plants such as Bt corn, cotton, potatoes, rice, and tomatoes constantly produce the Bt endotoxin, and thus speed up the spread of Bt resistance among pests that feed on these
A protest of genetically modified foods in front of the regional headquarters of the United Nations in Thailand. Critics of genetically modified foods cite concern over the possibility that modified foods might have unexpected and dangerous properties.
[© AFP/Corbis. Reproduced by permission.]
plants. They may also reduce insect diversity and population numbers among harmless and beneficial insects.
- Pesticide-resistant insects and the demise of safe pesticides. Most of the common genetically modified crops contain a gene that produces a protein which is toxic to a specific pest. However, exposing pests to toxins may stimulate resistance by the pests and render the pesticides useless.
Typically, when a new crop is created, whether by traditional methods or genetic modification, breeders conduct field testing for several seasons to make sure only desirable changes occur. Appearance, growth characteristics, and taste of the food are checked, and analytical tests to determine changes in nutrients and safety are performed. According to the U.S. Department of Agriculture, there is no evidence that any genetically modified foods now on the market pose any human health concerns or are in any way less safe than crops produced through traditional breeding. In 2002, however, the European Union updated and strengthened existing regulations and labeling laws for genetically modified foods in the European markets.
The Food and Agriculture Organization (FAO) of the United Nations recognizes that genetic engineering has the potential to help increase productivity in agriculture, forestry, and fisheries. However, the FAO urges caution to reduce the risks associated with transferring toxins from one organism to another, of creating new toxins, or of transferring allergenic compounds from one organism to another. The FAO acknowledges potential risks to the environment, including outcrossing (crossing unrelated organisms), which could lead to the evolution of more aggressive weeds, pests with increased resistance to diseases, or environmental stresses that upset the ecosystem balance.
Labeling of Genetically Modified Foods
According to the Institute of Food Technologists, genetically modified foods should not be labeled because "labels are likely to mislead consumers by implying a warning. . . . Moreover, labeling rDNA-engineered foods would not be economically prudent." In the European Union, concern about the safety of genetically modified organisms, fanned by years of political activism, has resulted in regulations that keep many genetically modified foods out of the European market. These regulations include requirements for tracing the genetic origin of each food ingredient, and for labeling the resulting products accordingly. Fueled by consumer protest and demand, lawmakers in China and Canada have recently begun discussing stricter labeling laws as well.
Genetic modification of foods is an area of biotechnology that is developing very rapidly, with many potential applications for improving the quantity and quality of the food supply. As with any new food technology, however, the safety of the products derived from this technology must be carefully assessed. Consumer concerns will likely continue to fuel the debate.
M. Elizabeth Kunkel Barbara H. D. Luccia
Institute of Food Technologists (2000). "Genetically Modified Organisms: A Backgrounder." Food Technology 54:42–45.
International Food Information Council (2000). Food Biotechnology: A Communications Guide to Improving Understanding. Washington, DC: Author.
Food and Agriculture Organization of the United Nations (2000). "FAO Statement on Biotechnology." Available from <http://www.fao.org/biotech>
United States Department of Agriculture (2002). "Agricultural Biotechnology." Available from <http://www.usda.gov/agencies>
World Health Organization (2002). "Foods Derived from Modern Biotechnology." Available from <http://www.who.int>