RISK FACTORS OF genetically modified organisms (GMOs). There are a number of publications which address this issue. Maclean and Laight (2001) and Dunham (1999) have produced very useful reviews which discuss many of the points raised in this paper. Summary: As the prevalence of genetically modified organisms (GMOs) continues to rise, there has been an increasing public interest for information concerning the safety of these products. Concerns generally focus on how the GMO may affect the environment or how it may affect the consumer. One specific concern is the possibility for GMOs to negatively affect human health. This could result from differences in nutritional content, allergic response, or undesired side effects such as toxicity, organ damage, or gene transfer. To address these concerns, there have been over 100 research studies comparing the effects of traditional food to genetically modified food, the results of which have been reviewed in various journals . How these results affect regulation can be found through The Center for Environmental Risk Assessment, which hosts a GM Crop Database that can be searched by the public to find GMO crop history, style of modification, and regulation across the world . Though knowing who to trust and what to believe regarding this topic is an ongoing battle, major health groups, including the American Medical Association and World Health Organization, have concluded from the research of independent groups worldwide that genetically modified foods are safe for consumers . Regarding toxicity, this includes any dangers related to organ health, mutations, pregnancy and offspring, and potential for transfer of genes to the consumer.
A significant percentage of processed foods purchased today contain some genetically engineered (GE) food products. As a result, each day, tens of millions of American infants, children and adults eat genetically engineered foods without their knowledge. Consumers have no way of knowing what foods are genetically engineered because the U.S. Food and Drug Administration (FDA) does not require labeling of these products. What’s worse, the agency also does not require any pre-market safety testing of GE foods. The agency’s failure to require testing or labeling of GE foods has made millions of consumers into guinea pigs, unknowingly testing the safety of dozens of gene-altered food products.
The FDA, in its response to a lawsuit filed by the Center for Food Safety in 1998, admitted in court that it had made “no dispositive scientific findings,” whatsoever, about the safety of genetically engineered foods. In other words, the FDA has given the biotech industry carte blanche to produce and market any number of genetically engineered foods without mandatory agency oversight or safety testing and without a scientific showing that these foods are safe to consume.
Quietly, biotechnology corporations are creating crops to produce proteins that are pharmaceuticals, vaccines, industrial enzymes or reagents for biochemical laboratories. Genetically engineered (GE) “pharm” crops are mostly grown in open fields, then after harvest the novel protein is purified for use. Most pharm crops are in pre-commercial field trials, but at least two proteins used in biochemical and diagnostic procedures are already being grown in corn for commercial use – avidin and beta-glucuronidase. Other proteins from pharm crops are already in clinical trials. Open field trials of pharmaceutical crops have been taking place every growing season in the US since 1992.
Corn is by far the most popular biopharm crop. Other crops engineered for biopharmaceutical production include soybeans, rice, barley, wheat, canola and tobacco. Biopharm field trials have been conducted on at least 900 acres, probably closer to 1600. The exact figure is not known because the USDA classifies these field trials as “confidential business information.”
None of the companies have a commercial permit for the cultivation of these crops. In the case of avidin and beta-glucuronidase, the companies are selling the chemical in commercial channels, but hiding their actions behind a “research” permit provided by the USDA. With this type of permit, the chemicals and field locations can be kept secret.
About 20 companies worldwide are developing plants for the production of pharmaceutical or industrial proteins. Companies have already conducted open field trials of plants that produce Hepatitis B vaccine, human antibodies against herpes and other diseases, and human blood proteins. One company is developing an animal drug in corn, and suggests that the corn would be grown only for feed. Field trials have taken place at least in the US, France, and Canada.
In our view the most important areas of risks which need to be considered in the use of transgenics are:
1. human health
3. animal welfare
4. poor communities
In each of these categories there exists a multiplicity of pathways by which effects could, in principle, be brought about. Rational and responsible assessment of risk requires that the following properties are all considered:
1. source of the DNA of the target gene;
2. source of the non target DNA segments of the construct used;
3. site(s) of incorporation of the transgene within the recipient genome;
4. product of the transgene;
5. interaction of the transgenic product with other molecules in host and consumer;
6. possible molecular changes in transgene product during processing;
7. pleiotropic effects of transgene;
8. tissue specificity of transgenic expression; and
9. numbers of transgenic organisms capable of interacting with natural systems).
9.1 Human health
The risks to health will depend upon all of the factors listed above. In practical terms the most important of these are likely to be the source of the DNA and the nature of the product.
The great majority (98 percent) of dietary DNA is degraded by digestive enzymes relatively quickly (Royal Society, 2001) but use of viruses (disarmed or otherwise) as vectors, must increase the risk factor significantly as these are organisms which are adapted to integrating into host genomes and some represent risk factors for cancer induction. The work of Zhixong Li et al. (2002) who induced leukaemia by using retroviral vectors in making transgenics for a commonly used marker gene in mice and a recent report of leukaemia induction in a child undergoing gene therapy for x-SCID using a retrovirus (Hawkes, 2002) show that this is not a trivial risk. Arguments about risks and benefits attached to this form of gene therapy are current (Kaiser, 2003).
At the other extreme the use of autotransgenics must be seen as posing a risk which is orders of magnitude lower than that for allotransgenics and probably negligible. The major risk from the production of the transgene will lie in the use of novel proteins or other molecules produced by the transgenic organisms. Either in the native form or, following modifications in the human body, such molecules could be inimical to human health (e.g. through allergies). It would seem sensible to avoid the use of such substances except where strictly necessary and under rigorous control.
Other potential risks may lie in incorporation of transgenic DNA into the genomes of resident gut microflora (though this is likely to be very improbable) or a change in the pathogen spectrum of the transgenic fish leading to it hosting a new pathogen which happens to be also a human pathogen.
Maclean and Laight (2000) assessed risks to consumers as “very low”.
The extent of aquatic diversity is both extremely large and relatively poorly understood (Beardmore, Mair and Lewis, 1997). This means that the task of estimating the risks to aquatic biodiversity at all of its levels from the use of GMOs or indeed, any genetically distinctive strain used in aquaculture is monumentally large. Aquaculture has a further problem in that the (almost always unintended) escapes of genetically distinct farmed fish are unpredictable and often large in numbers. Stenquist (1996) in discussing transgenics in open ocean aquaculture, quotes some relevant figures. Thus, 15 percent escapes for Atlantic salmon, escapes of 150 000 salmon and 50 000 trout in Chile and catch statistics for Atlantic salmon off Norway in which 15?20 percent of the fish caught were of farmed origin. In Scotland an escape of 100 000 Atlantic salmon was reported recently. It is clear that escapes of these magnitudes pose considerable problems and it is not surprising that in some parts of Norway fish of farmed origin represent a majority of the animals fished (Saegrov et al., 1997)
The major focus of attention in the literature lies, understandably, upon the effects of escapes upon natural populations of the same species, but we must always bear in mind possible impacts across an assemblage or ecosystem as a whole. The first general point to make is that there is, in principle, no difference between the biodiversity risks from escapes of GMOs and from fish genetically improved in some other way, e.g. by selective breeding or (in some respects) from exotic species.
The second general principle is that such genetically improved forms including GMOs, are developed for a specific set of environmental circumstances in which they enjoy an advantage conferred by human decisions. In nature, however, such genetically distinct forms may legitimately be regarded as mutant forms of the wild type. A considerable body of genetical knowledge tells us that the probability of survival of mutant forms is extremely low because they are disadvantaged in viability and/or fertility under natural conditions. Thus, for example, in the genetically distinct farmed Atlantic salmon in Norway the males are very much less successful than wild males in securing mates (Jonssen, 1997).
However, it must be conceded that in species like salmon where the farmed populations outnumber the wild populations by orders of magnitude, the effects of escapes of any genetically distinct genotype upon natural populations may be both deleterious and of significant size simply as a result of “swamping”
An interesting model of the effects on a medaka (Oryzias latipes) population of transgenic release has been produced by Muir and Howard (2001) using estimates of juvenile and adult viability, age at sexual maturity, female fecundity, male fertility and mating advantage. They were able to demonstrate that the transgene would spread in natural populations, despite low juvenile viability, if transgenes have sufficient high positive effects on other fitness components. It has been argued that this might lead to extinction but the selective pressure for recombinant genomes with higher viability would be expected to be immense.
Maclean and Laight (2000) simulated the changes in frequency of a transgene expected with different scenarios embracing a range of selective values including heterozyote advantage. They note that “repeated small introductions [of the transgene] can have an effect on … frequency … since the frequency of advantageous alleles rises much more rapidly than if a single large introduction is considered”.
A major problem in assessing risk to natural populations is that of scale. Even if farmed fish are at a selective disadvantage in natural conditions, the ratio of wild:farmed numbers may in some areas, be relatively small. In these situations significant modification of the “native” population and its role in the ecosystem is inevitable.
Whilst not providing a completely satisfactory answer, there is little doubt that making farmed fish sterile would go a long way towards reducing the pressure upon such threatened ecosystems. A number of research efforts to develop systems for sterile fish production are being made. The techniques include triploidisation, antisense transgenics, ribozymes and gene targeting (Maclean, 2002; Uzbekova et al., 2001; Maclean, pers. com.).
Provided that the best containment measures (physical and biological) are adopted, in our opinion, in general risks to biodiversity by GMOs per se are probably extremely small, but in specific cases, the risks and consequences may be large. As a general rule and adopting a precautionary approvah (OECD, 1995), it is, however, clear that each individual case needs careful study and appraisal and the best possible containment measures before approval for uptake into commercial production is given.
9.3 Animal welfare
The direct or indirect effects of transgenesis upon the welfare of fish GMOs in aquaculture are very poorly understood. In part, no doubt, this is because notions of cruel or unnatural treatment in mammalian species translate, for a variety of reasons, imperfectly to fish. Nevertheless, as life forms with highly developed nervous systems and with a range of behavioural phenotypes which flow from this, fish qualify for welfare consideration.
There are a few studies which bear on this. Thus, for example, Devlin et al. (1995b) reported changes in colouration, cranial deformities and opercular overgrowth and lower jaw deformation in coho salmon transgenic for AFP and GH. After one year of development anatomical changes due to growth of cartilage in the cranial and opercular regions were more severe and reduced viability was evident.
The larger body of data on species farmed terrestrially shows dysfunctional development leading to acromegaly, lameness and infertility in some GH transgenics in pigs and sheep. However, in pigs dietary modification influencing nutritional levels of zinc proved successful in avoiding such abnormalities (Pursel and Solomon, 1993; Pursel, 1998).
We have been unable to find systematic data on the incidence, in fish GMOs, of effects such as those described by Devlin et al. (1995b) and this is probably because animal welfare is not sufficiently widely recognised as an issue in relation to the use of GMOs. This is well illustrated in the otherwise comprehensive and balanced review by Sin (1997) in which the section on ethical issues contains no reference to animal welfare. Nevertheless, if GMOs are to be used in aquaculture (and there are weighty arguments for so doing), concerns on this issue will need to be properly satisfied. The Royal Society report (2001) devotes a significant amount of space to this issue.
9.4 Poor communities
This term rather than poor countries is used because all poor countries contain rich people and rich communities. The possible economic disadvantages of use of transgenics centre on two issues:
9.4.1 Dependence on external agencies for seed fish
If transgenic fish become widely grown because they are much more efficient, and if special broodstock are required to produce fry for on-growing to adults, which, cannot be used as broodstock, a dependency is created. This dependency may be benign or oppressive, depending on the arrangements made for seed supply.
9.4.2 Intellectual property rights
This is a very difficult issue indeed. Since genes may now be patented and therefore, enjoy commercial value, the opportunities for dispute about equitable treatment of stakeholders in cases where ownership of genes and strains is contested, are legion.
A recently published report (Commission on Intellectual Property Rights, 2002) states that developing countries are frequently disadvantaged in the use of, and access to, IPR because of increasingly protective attitudes taken by owners of IPR. However, the report also indicates that developing countries are very heterogeneous in respect of their ability to use and develop IPR.
Along with its approval of GE foods, the FDA in 1993 also approved the use of genetically engineered recombinant Bovine Growth Hormone (rBGH), used to induce dairy cows to produce more milk. At the time the FDA assured consumers that the milk was safe. Since then, however, regulatory bodies in both Canada and Europe have rejected the drug, citing numerous animal and human health concerns. Perhaps of most immediate concern for consumers is that research shows that the levels of a hormone called insulin-like growth factor-1 (IGF-1) are increased in dairy products produced from cows treated with rBGH. The Canadians and Europeans further found that the FDA had completely failed to consider a study which showed that the increased IGF-1 in rBGH milk could survive digestion and make its way into the intestines and blood streams of consumers. These findings are significant because numerous studies now demonstrate that IGF-1 is an important factor in the growth of breast cancer, prostate cancer, and colon cancer.
The genetic engineering of food creates two separate and serious health risks involving allergenicity. The first is that genetic engineering can transfer allergens from foods to which people know they are allergic, to foods that they think are safe. This risk is not hypothetical. A study by the New England Journal of Medicine showed that when a gene from a Brazil nut was engineered into soybeans, people allergic to nuts had serious reactions to the engineered product. At least one food, a Pioneer Hi-Bred International soybean, was abandoned because of this problem. Without labeling, people with known food allergies have no way of avoiding the potentially serious health consequences of eating GE foods containing hidden allergenic material.
There is another allergy risk associated with GE foods. These foods could be creating thousands of different and new allergic responses. Each genetic “cassette” being engineered into foods contains a number of novel proteins (in the form of altered genes, bacteria, viruses, promoters, marker systems, and vectors) which have never been part of the human diet. Each of these numerous novel proteins could create an allergic response in some consumers. The FDA was also well aware of this new and potentially massive allergenicity problem. The agency’s scientists repeatedly warned that genetic engineering could “produce a new protein allergen.”
Once again the agency’s own scientists urged long-term testing. However, the FDA again ignored its own scientists. Because these foods were allowed to be marketed without mandatory testing for this kind of allergenicity, millions of unsuspecting consumers have continuously been exposed to a potentially serious health risk. This FDA action is especially negligent in that the potential consequences of food allergies can include sudden death, and the most significantly affected population is children.
Genetically engineered foods are inherently unstable. Each insertion of a novel gene, and the accompanying “cassette” of promoters, antibiotic marker systems and vectors, is random. GE food producers simply do not know where their genetic “cassette” is being inserted in the food, nor do they know enough about the genetic/chemical makeup of foods to establish a “safe” place for such insertions. As a result, each gene insertion into a food amounts to playing food safety “roulette,” with the companies hoping that the new genetic material does not destabilize a safe food and make it hazardous. Each genetic insertion creates the added possibility that formerly nontoxic elements in the food could become toxic.
FDA was well aware of the “genetic instability” problem prior to establishing their no-testing policy. FDA scientists warned that this problem could create dangerous toxins in food and was a significant health risk. The scientists specifically warned that the genetic engineering of foods could result in “increased levels of known naturally occurring toxicants, appearance of new, not previously identified toxicants, [and] increased capability of concentrating toxic substances from the environment (e.g., pesticides or heavy metals).” These same FDA scientists recommended that long term toxicological tests be required prior to the marketing of GE foods. FDA officials also were aware that safety testing on the first genetically engineered food, the Calgene Flavr Savr tomato, had shown that consumption of this product resulted in stomach lesions in laboratory rats.
FDA’s response to the potential toxicity problem with genetically engineered foods was to ignore it. They disregarded their own scientists, the clear scientific evidence and the deaths and illnesses already attributed to this problem. The agency refused to require pre-market toxicological testing for GE foods or any toxicity monitoring. FDA made these decisions with no scientific basis and without public notice and comment or independent scientific review. The agency’s actions can only be seen as a shameful acquiescence to industry pressure and a complete abandonment of its responsibility to assure food safety.
Another hidden risk of GE foods is that they could make disease-causing bacteria resistant to current antibiotics, resulting in a significant increase in the spread of infections and diseases in the human population. Virtually all genetically engineered foods contain “antibiotic resistance markers” which help the producers identify whether the new genetic material has actually been transferred into the host food. FDA’s large-scale introduction of these antibiotic marker genes into the food supply could render important antibiotics useless in fighting human diseases. For example, a genetically engineered maize plant from Novartis includes an ampicillin-resistance gene. Ampicillin is a valuable antibiotic used to treat a variety of infections in people and animals. A number of European countries, including Britain, refused to permit the Novartis Bt corn to be grown, due to health concerns that the ampicillin resistance gene could move from the corn into bacteria in the food chain, making ampicillin far less effective in fighting a wide range of bacterial infections.
Again, FDA officials have ignored their own scientists’ concerns over the antibiotic resistance problem. Meanwhile, the British Medical Association (BMA) addressed this problem in its own study of GE foods. The BMA’s conclusion was unequivocal: “There should be a ban on the use of antibiotic resistance marker genes in GM food, as the risk to human health from antibiotic resistance developing in microorganisms is one of the major public health threats that will be faced in the 21st century.”
The well-respected British medical journal, The Lancet, published an important study conducted by Drs. Arpad Pusztai and Stanley W.B. Ewen under a grant from the Scottish government. The study examined the effect on rats of the consumption of potatoes genetically engineered to contain the biopesticide Bacillus Thuringiensis (B.t.). Thescientists found that the rats consuming geneticallyaltered potatoes showed significant detrimentaleffects on organ development, body metabolism, and immune function.
The biotechnology industry launched a major attack on Dr. Pusztai and his study. However, they have as of yet not produced a single study of their own to refute his findings. Moreover, twenty-two leading scientists recently declared that animal test results linking genetically engineered foods to immuno-suppression are valid.
Loss of Nutrition
Genetic engineering can also alter the nutritional value of food. In 1992, the FDA’s Divisions of Food Chemistry & Technology and Food Contaminants Chemistry examined the problem of nutrient loss in GE foods. The scientists involved specifically warned the agency that the genetic engineering of foods could result in “undesirable alteration in the level of nutrients” of such foods. They further noted that these nutritional changes “may escape breeders’ attention unless genetically engineered plants are evaluated specifically for these changes.” Once again, the FDA ignored findings by their own scientists and never subjected the foods to mandatory government testing of any sort.
GMO toxicity: fears and scientific analysis
After genetically modified foods were introduced in the United States a few decades ago, people independently reported toxic effects caused by GMOs. One example is an anti-GMO advocacy group called the Institute for Responsible Technology (IRT), which reported that rats fed a diet containing a GMO potato had virtually every organ system adversely affected after just ten days of feeding . The IRT stated that the toxicity was the result of genetic modification techniques and not a specific case for that particular potato. They claimed the process of making the GMO caused it to be toxic and thus all GMOs were high risk for toxicity.
Scientists across the U.S. and the rest of the world have sought to rigorously test the assertions of the IRT and others to uncover any possible toxicity caused by GMOs. To this end, many different types of modifications in various crops have been tested, and the studies have found no evidence that GMOs cause organ toxicity or other adverse health effects. An example of this research is a study carried out on a type of GMO potato that was genetically modified to contain the bar gene. The product of the bar gene is an enzyme that can detoxify herbicides and thus protects the potato from herbicidal treatment.
In order to see if this GMO potato would have adverse effects on consumer health like those claimed by the IRT, a group of scientists at the National Institute of Toxicological Research in Seoul, Korea fed rats diets containing either GMO potato or non-GMO potato . For each diet, they tracked male and female rats. To carefully analyze the rats’ health, a histopathological examination of tissues and organs was conducted after the rats died. Histopathology is the examination of organs for disease at the microscopic level (think pathologist doing a biopsy). Histopathological examinations of the reproductive organs, liver, kidneys, and spleen showed no differences between GMO-eating and non-GMO-eating animals.
Three years earlier, a separate group had found the same results for a GMO tomato and a GMO sweet pepper . These researchers had split rats into four diet groups: non-GMO tomato, GMO tomato, non-GMO sweet pepper, and GMO sweet pepper. They fed the rats over 7,000 times the average human daily consumption of either GMO or non-GMO tomato or sweet pepper for 30 days and monitored their overall health. Finally, they carried out histopathology and again found no differences in the stomach, liver, heart, kidney, spleen, or reproductive organs of GMO versus non-GMO fed rats. Despite massive ingestion of GMO potato, tomato, or sweet pepper, these studies demonstrated no differences in the vitality or health of the animals, even at the microscopic level.
Experiments like these on humans would be completely unethical. Fortunately, prior to these studies years of work have demonstrated that rodents, like mice and rats, are acceptable models for humans, meaning rodent responses to drugs, chemicals, and foods can predict human response. Rat feeding studies like these, in which rats are fed a potential toxic item and monitored for adverse effects, are considered both specific and sensitive for monitoring toxicity of foods and widely used in the food regulation industry .
The test of time: GMOs and their effect on our offspring
Although scientists have been able to demonstrate that GMOs are not toxic to the animals that eat them, as described above and elsewhere, what about side effects being passed on to our next generations?
To discern whether GMO crops affect fertility or embryos during gestation, a group from South Dakota State University again turned to studies on rats. In this case, the rats were eating a type of GMO corn, more commonly known as Bt corn. Bt stands for Bacillus thuringiensis, a microbe that produces insecticidal endotoxin and has been used as a topical pesticide against insects since 1961 (see this article). To allow corn to directly generate this endotoxin, scientists introduced a gene from Bt into the genetic material (DNA) of corn.
To address buildup of toxicity over time, this group monitored the GMO-eating rats not only for the lifetime of one generation, but also three additional generations. For each generation, they tracked the fertility of parents and compared the health of the embryos from parents that ate Bt corn to those with parents that did not . Toxic effects can arise in many places and in many ways, but some organs are more susceptible to damage than others, and monitoring them is a good readout for other difficult-to-see effects. Testes are considered a particularly sensitive organ for toxicity tests because of the high degree of cell divisions and thus high susceptibility to cellular or molecular toxins. To examine the affect of Bt corn on testicular health, the researchers tracked testicular development in fetal, postnatal, pubertal, and adult rats for all four generations. The group found no change in testicular health or litter sizes in any generation. Likewise, ingestion by pregnant mothers had no effect on fetal, postnatal, pubertal, or adult testicular development of her offspring.
Other groups have monitored toxicity over time as well. For example, the group studying the bar GMO potato also wanted to see if organs and reproductive health were sensitive to GMOs over long exposure times . To do this, they examined the fertility and gestation periods of GMO-eating mothers compared to non-GMO-eating mothers for five generations. They tracked animal body weight, bone, eye, and thymus development, and general retardation. Like the studies on Bt corn, in all cases, they found no significant differences between the GMO potato and non-GMO potato diets, suggesting that there is no buildup or inheritance of toxicity, even over multiple generations.
Figure 1. Work from independent researchers has investigated various aspects of GMO safety, especially concerning consumer health and toxicity.
Can GMOs change our genes?
Concern has also surrounded the idea that genetically modified DNA would be unstable, causing damage (via unintentional mutations) not only to the crop, but also to whomever would consume it. Mutations in DNA are closely tied to cancer and other diseases, and thus mutagenic substances can have dire effects on human health. The creation of mutations, called mutagenesis, can be measured and compared to known mutation-causing agents and known safe compounds, allowing researchers to determine whether drugs, chemicals, and foods cause increased mutation rates. There are a variety of ways to measure mutagenicity, but the most traditional method is a process pioneered by Bruce Ames at the University of California in Berkeley. His method, now called the Ames test in his honor, is able to track increased rates of mutations in a living thing in response to some substance, like a chemical or food.
To directly test the ability of a GMO to cause mutations, a research group from the National Laboratory of Protein Engineering and Plant Genetic Engineering in Beijing, China applied the Ames test to GMO tomatoes and GMO corn . GMO tomatoes and corn express the viral coat protein of cucumber mosaic virus (CMV). Expression of this coat protein confers resistance to CMV, which is the most broadly infectious virus of any known plant virus, thought to infect over 1,200 plant species from vegetable crops to ornamentals. The results of the Ames test demonstrated no relationship between GMO tomatoes or corn and mutations. They repeated their analysis using two additional methods for analyzing mutagenicity in mice and got the same result, allowing them to conclude that genetically modified DNA did not cause increased mutations in consumers. The modified DNA, like unmodified DNA, was not mutagenic.
Mutagenicity aside, there are also concerns surrounding the ability of the modified DNA to transfer to the DNA of whomever eats it or have other toxic side effects. Depending on the degree of processing of their foods, a given person will ingest between 0.1 and 1 g of DNA each day ; as such, DNA itself is regarded as safe by the FDA . To determine if the DNA from GMO crops is as safe to consume as the DNA from traditional food sources, the International Life Sciences Institute reviewed the chemical characteristics, susceptibility to degradation, metabolic fate and allergenicity of GMO-DNA and found that, in all cases, GMO-DNA was completely indistinguishable from traditional DNA, and thus is no more likely to transfer to or be toxic to a human . Consistent with this, the researchers working on the GMO potato attempted to isolate the bar gene from their GMO eating rats. Despite 5 generations of exposure to and ingestion of the GMO, the researchers were unable to detect the gene in the rats’ DNA .
A strong argument for GMO health safety
After more than 20 years of monitoring by countries and researchers around the world, many of the suspicions surrounding the effects of GMOs on organ health, our offspring, and our DNA have been addressed and tested (Figure 1). In the data discussed above, alongside many more studies not mentioned here, GMOs have been found to exhibit no toxicity, in one generation or across many. Though each new product will require careful analysis and assessment of safety, it appears that GMOs as a class are no more likely to be harmful than traditionally bred and grown food sources.
Megan L. Norris is a Ph.D. candidate in the Molecular, Cellular and Organismal Biology Program at Harvard University.
This article is part of the August 2015 Special Edition, Genetically Modified Organisms and Our Food.
- European Food Safety Authority GMO Panel Working Group on Animal Feeding Trials. “Safety and nutritional assessment of GM plants and derived food and feed: the role of animal feeding trials.,” Food Chem. Toxicol., vol. 46 Suppl 1, pp. S2–70, Mar. 2008
- G. Flachowsky, A. Chesson, and K. Aulrich, “Animal nutrition with feeds from genetically modified plants.,” Arch. Anim. Nutr., vol. 59, no. 1, pp. 1–40, 2005.
- Cera-gmc.org, ‘Welcome to the Center for Environmental Risk Assessment | CERA’, 2015. [Online]. [Accessed: 11- Jul- 2015].
- Tamar Haspel. “Genetically modified foods: What is and isn’t true”. Washington Post. October 15, 2013.
- Jeffrey Smith. “GM Potatoes Damaged Rats.” Genetic Roulette, Section I: Documented Health Risks.
- G. S. Rhee, D. H. Cho, Y. H. Won, J. H. Seok, S. S. Kim, S. J. Kwack, R. Da Lee, S. Y. Chae, J. W. Kim, B. M. Lee, K. L. Park, and K. S. Choi, “Multigeneration reproductive and developmental toxicity study of bar gene inserted into genetically modified potato on rats.,” J. Toxicol. Environ. Health. A, vol. 68, no. 23–24, pp. 2263–2276, 2005.
- Z. L. Chen, H. Gu, Y. Li, Y. Su, P. Wu, Z. Jiang, X. Ming, J. Tian, N. Pan, and L. J. Qu, “Safety assessment for genetically modified sweet pepper and tomato,” Toxicology, vol. 188, no. 2–3, pp. 297–307, 2003.
- D. G. Brake, R. Thaler, and D. P. Evenson, “Evaluation of Bt (Bacillus thuringiensis) Corn on Mouse Testicular Development by Dual Parameter Flow Cytometry,” J. Agric. Food Chem., vol. 52, no. 7, pp. 2097–2102, 2004.
- D. A. Jonas, I. Elmadfa, K. H. Engel, K. J. Heller, G. Kozianowski, a. König, D. Müller, J. F. Narbonne, W. Wackernagel, and J. Kleiner, “Safety considerations of DNA in food,” Ann. Nutr. Metab., vol. 45, no. 6, pp. 235–254, 2001.
- FDA: Guidance to Industry for Foods Derived from New Plant Varieties, Section V (C).
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