Genetically modified foods have become a major concern and have caused controversy regarding both their health and environmental effects (2). ‘Using modern techniques of genetic engineering, it is possible to introduce specific genetic material derived from any species of plant, animal, or microorganism, or even a synthetic material, into different species of plant’ (Journal 1) This allows a desired trait to be enhanced and reproduced. (3) (4) ‘The resulting plants are commonly known as genetically modified (GM) plants; when used as food sources, they are known as GM foods.’ (Journal 1)
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‘It is probable that crop improvement began as soon as farming did’ (1) It is thought that improvement to crops and harvesting developed subconsciously with farmers selectively breeding animals and isolating, to then reproduce crops from those with the most desired attributes and from highly variable populations.(1) The first genetically modified crop was the tomato Flavr Savr, produced by a Californian company Calgene, in 1992 whose ‘intention was to create a vine-ripened tomato that was both ‘long-lasting and tasty’. (6) However the company failed to prevent the skin of the tomato from soften whilst the fruit ripened. It took 10 years for the development of the tomato, (6) but eventually it received FDA approval in 1994 (6), and led to an increase in GM food products available on the market.
Romania, Mexico, Germany, Australia and France are just a few of the 13 countries known to have grown genetically engineered crops on their land for commercial use in the year 2000. (7) The United States of America produced 68% of the worlds GM crops, and therefore became the largest producer of these crops. In comparison to this, Argentina produced, 23%, Canada, 7% and China only 1%. Statistics from 2007 have shown a substantial increase from 1.7 million hectares being used for growing Gm foods in 1996, to 143 million hectares in 23 countries around the globe, with 90% of GM food produced being in developed or newly-developed countries.(journal one).
Ways to make GM foods.
Genetic modification of a particular plant or animal species can be accomplished by a number of different ways. (3) Genetic engineering involves the DNA alteration of a plant or animal’s DNA which holds the genetic information of the species. It is the alterations of a specific gene that enables modification of certain characteristics displayed. In order to change a certain characteristic, the corresponding gene coding for it, must initially be isolated in order to be inserted into a new DNA strand using a transfer vector. A Vector ‘is an agent that can carry a DNA fragment into a host cell.’ (19) Plasmids are circular DNA molecules that are examples of vectors and ‘can replicate independently of the host cell.’ (3) Once the gene is present in the transfer vector it can then be directed into the cells of the target organism. Then inside the cell the vector replicates and becomes part of the cell’s own DNA, altering the organism’s characteristics.
Similar to this method is the vector technique which involves the products being inserted directly into genome via another vector. As well as this there is also the biolistic method, which is commonly known as the gene-gun method and is a technique predominantly used in plant modification. (20) Pellets of metal ‘coated with the desirable DNA’ are fired at the target cells which are then allowed to reproduce, and may possibly be cloned in order to produce a ‘genetically identical crop.’ (20)
Advantages and disadvantages of GM foods
With the world’s population expected to reach 12 billion in the next 50 years, the demand for high quality produce will continue to increase. By growing genetically modified plants with a resistance to pests or herbicides, then the use of chemical applications may be reduced, as can the costs of producing a crop, damage by unwanted pests/weeds.(8)
With the rise of various different virus’, diseases and bacteria that effect and inhibit the growth of a crop, technologies have enabled genetically engineered crops to be resistant to these different diseases. (9)Plants such as tobacco and potato have had antifreeze genes introduced in to them, to encourage the plants to withstand cold temperatures that would normally kill such plants. (10)
A common problem in third world countries is malnutrition with estimations of 1.02 billion people being undernourished and starved. (13) The main staple diet for these people is rice which unfortunately does not contain sufficient quantities of the nutrients and vitamins required to help prevent malnutrition. Genetically engineering this crop in order to create a nutritionally enriched rice variety would have the potential to help improve and in turn, eliminate these deficiencies. Vitamin A deficiency, estimated to affect millions of people around the world prompted the design of ‘Golden rice’ researched by Ingo Potrykus and Peter Beyer and contained very large quantities of beta-carotene, which the body uses and coverts to Vitamin A, and is required for a number of different metabolic functions including in vision, immune functions and bone metabolism. (3)
‘Genetic engineering techniques are now more commonly being used in order to introduce into plants, particular DNA that leads to the expression of distinct and unique proteins that are of specific interest and may be harvested and used in the ‘…production of pharmaceutical compounds.’ (11) Currently, synthesis of plant-derived proteins intended for pharmaceutical use is still in the early development stages. Examples of the types of protein and their intended use are summarised in the table below.
Some examples of GM plants with improved characteristics designed to improve health and nutrition are Maize with added vitamin C content, Potato with insulin as well as enhanced calcium levels, rice with added iron or zinc and coffee beans with decreased caffeine content. (journal 2)
One study in to which a genetically modified green pepper and a standard unmodified pepper were analyzed for their nutrient and mineral contents and showed no significant opposing results between the two peppers. The analysis showed that there was neither significant difference in the energy and the protein levels nor a difference in the mineral content which included calcium, phosphorus, iron, sodium, potassium, magnesium, and zinc. This therefore concluded that, the nutrient composition of the genetically modified green pepper was found to be equivalent to that of the standard unmodified peppers. (journal 11)
Another study that tested genetically modified Bt maize on laying quails also gave a similar conclusion to the green pepper study. (Flachowsky et al., 2005b; Halle et al., 2006).The results showed that ‘Bt maize did not significantly influence health, hatchability and performances of quails nor did it affect the quality of meat and eggs of quails’ compared with the unmodified maize that was also tested. (journal 2) One exception to this study however was the that performed by Piva et al. (2001a,b) who noted that ‘significantly improved animal performance was associated with a diet containing the Bt maize.’ It is thought that this ‘improved performance’ demonstrated by the animals fed the genetically modified Bt maize crop, was because it reduced ‘secondary fungal infection and, as a consequence, reduced mycotoxin contamination.’ (journal 2)
‘Publications on GM food toxicity are scarce’. Although there are many arguments and opinions surrounding the toxicity of GM foods, there is little experimental data and analysis to construct such arguments. ‘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’ (18)
Acute toxicity studies on the ‘Flavr Savr’ genetically modified tomatoes, required by the FDA, were carried out with rats to determine toxic effects of the GM product. ‘It was concluded that mean body and organ weights, weight gain, food consumption and clinical chemistry or blood parameters were not significantly different between GM-fed and control groups.’ However it was noted that sections of the stomach in up to 7 of the 20 female rats fed the GM tomato, showed ‘mild/moderate erosive/necrotic lesions’ and as well as this 7 of the 40 rats involved in the experiment were known to have died a few weeks after for unstated reasons. (18)
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Another experiment that tested herbicide-resistant GM maize ‘showed significant differences in fat and carbohydrate contents compared with non-GM maize.’ Toxicity tests were performed and showed that the ‘rats ability to digest was decreased after eating GM corn.’ (18) Likewise tests in to ‘potatoes transformed with a specific toxin gene or the toxin itself was shown to have caused an array of unwanted effects and showed that, CryI toxin was indeed stable in the gut of the mouse and ‘therefore GM crops expressing it need to be subjected to “thorough tests…to avoid the risks before marketing.’ (18) Such studies support people’s concerns about GM foods and highlight the need for further research in to them and their health effects.
Another issue with the rise in the production of genetically modified crops is the transfer of allergens in to new crops and the effects of particular allergens on human immune response. (journal 3) The majority of dietary proteins consumed are hydrolysed, and digested into smaller peptides that do not produce immune response in most people. However for those unfortunate enough to have hypersensitivity disorders, allergic type inflammatory responses can occur when contact with certain foods is made. ‘For this reason, the introduction of genetically modified plants into the human food chain that contain allergens or proteins of unknown allergic potential could be of risk’. (Journal 8) Nordlee et al. (1996) cited in (journal 8) demonstrated using the Brazil nut protein that allergenicity was indeed transferable by genetic modification. Amongst other things these studies confirmed concerns that ‘sensitivity could be transferred to transgenic plants when an allergen is expressed in a non-native host through genetic modification.’ (journal 8)
Lee et all (2006) compared the allergenicity of GM potatoes with that of non- GM potatoes in which 1886 patients who suffered various allergic diseases etc were used for testing. From his study he was able to conclude that genetic modification of crops did not cause an increase in allergenicity.
The use of certain ‘animal models’ has ‘been developed in order to test whether or not food components such as GM proteins could potentially induce allergic reactions. (journal 2) The animals are often responders to high IgE and are sensitised before given the ‘test compound.’ The animal models all have in common the production of specific IgE antibodies to the specific proteins. Particular proteins that cause food allergy in humans are claimed to produce more pronounced IgE responses whereas proteins that do not readily cause such effects in humans are claimed to induce poor IgE responses. (Journal 2)
An example of one such model is the BN rat which is a ‘high-immunoglobulin (particularly IgE) responder strain’ and is similar to humans in the way that they produce ‘antigen-specific immunoglobins’,-which are glycoprotein’s that function as certain antibodies. (3) Experimental investigations in to the hypersensitivity of rats to specific proteins performed by Knippels et al., 1998, showed the rats were capable of producing specific antibodies (IgG and IgE) and immune responses to the model antigen ‘ovalbumin’, found in egg white and often employed in experiments into immunology and hypersensitivity to stimulate allergic reactions. (3) Analysis of the research showed the rats developed allergic responses to the same problematic proteins that cause reactions in humans. (Knippels & Penninks, 2002). (Journal 8)
One of the most impressive applications of genetic engineering is now the development of so-called “pharma crops.”‘ Specific genes in some useful plants are modified with in order for certain chemicals, antibodies, hormones and proteins to be produced that can be used in different applications in the pharmaceutical industry. (14)
The company, INB Biotechnologies in Philadelphia have been recently designing a ‘nontoxic anthrax vaccine through the transgenic modification of petunias.’ This causes the production of new proteins by the plant that in turn causes the development of antibodies against the anthrax bacterium, when consumed. (16) Trials have begun on genetically engineered crops designed for ‘healing wounds and treating conditions such as cystic fibrosis, cirrhosis of the liver and anaemia; antibodies to fight cancer and vaccines against rabies, cholera and foot-and-mouth disease.’ (15)
The concept of genetically engineered crops for pharmaceutical use is a fairly new idea, and therefore such products are still in their preliminary stages of design and testing. However significant concern has been raised surrounding their use and possible consequences. For instance it is thought that food crops already are or may in the future, be ‘contaminated by DNA sequences from GM crops.’ (15) Genetically modified crops run the risk of eventually introducing unknown, potentially harmful chemicals into the food chain, by accidental cross breeding and seed contamination. (17)
As well as there being many benefits to genetic engineering and the introduction of genetically modified foods, there are as well, possible dangers and hazards leading to concern over their use and potential risks to both the environment and to humans. However there is inconsiderable evidence to suggest that there are disadvantages and significant risks of consuming GM foods. Various testing has been conducted on an array of substances and components of GM crops to test for certain effects, some of these being toxicity and allergenicity. There are conflicting reports; some suggesting GM foods are safe, others that say they are dangerous and a risk to human health.
Although only slight effects have been observed on the animals tested, it is enough to warrant anxiety over GM foods and their possible implications on humans. Some would argue minor changes and effects on animals doesn’t necessarily mean that they would have the same effect, if consumed, on humans, yet, there have also been a number of experiments that contradict this and analysis of which conclude little or no clinical, toxicological abnormalities observed in the animals having been tested.
It has been demonstrated that Genetic modification as well as being advantageous can also increase the nutritional value of a food source, providing useful benefits, such as crops with extra vitamins/minerals etc such as the example of ‘golden rice’ highlighted above. However there are also significant disadvantages such as possible toxicity and allergic components in some GM food sources. Having looked at the evidence surrounding such factors it is difficult to say whether or not there are nutritional arguments against genetically modified foods. It is safe to say therefore, that new and improved methods are needed to further investigate the ‘compositional, nutritional, toxicological and metabolic differences between GM and conventional crops’ likewise the ‘techniques used in developing GM crops’ in order to expel the fears of many and allow for technology in this field to expand safely. (18)
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- Insecticidal proteins from Bacillus thuringiensis protect corn from corn rootworms (Nature Biotechnology, Vol 19, No 7, pp 668-672, Jul 2001) Lepidopteran-resistant transgenic plants (US Patent 6313378, Nov 2001, Monsanto) cited in (7)
- Transgenic Approaches to Combat Fusarium Head Blight in Wheat and Barley (Crop Science, Vol 41, No 3, pp 628-627, Jun 2001) Post-transcriptional gene silencing in plum pox virus resistant transgenic European plum containing the plum pox potyvirus coat protein gene (Transgenic Research, Vol 10, No 3, pp 201-209, Jun 2001) cited in (7)
- Type II fish antifreeze protein accumulation in transgenic tobacco does not confer frost resistance (Transgenic Research, Vol 8, No 2, pp 105-117, Apr 1999) cited in (7)
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- Risk assessment of genetically modified crops for nutrition and health- Javier A Magaña-Gómez and Ana M Calderón de la Barca
- Safety and nutritional assessment of GM plants and derived food and feed: The role of animal feeding trials- Report of the EFSA GMO Panel Working Group on Animal Feeding Trials
- Assessment of the safety of foods derived from genetically modified (GM) crops – A. Ko¨ niga,*, A. Cockburnb, R.W.R. Crevelc, E. Debruyned, R. Grafstroeme, U. Hammerlingf, I. Kimberg, I. Knudsenh, H.A. Kuiperi, A.A.C.M. Peijnenburgi, A.H. Penninksj, M. Poulsenh, M. Schauzuk, J.M. Wall
- Genetically modified plants and food hypersensitivity diseases: Usage and implications of experimental models for risk assessment A new oral sensitization model in rats to food proteins and the importance of dietary control in oral sensitization with soy- Knippels, LMJ; Penninks, AH; Spanhaak, S, et al
- The nutrient composition of the herbicide-tolerant green pepper is equivalent to that of the conventional green pepper Hongju Parka, Sunghyen Leea,c,4, Hyunjin Jeonga, Sumook Choa, Hyekyung Chuna, Ohhyun Backa, Donghern Kimb, Hyun S. Lillehojc
- Plant biotechnology. Ed, Nigel G. Halford (2006) chapter 1 pg5 John Wiley and sons Ltd west sussex, England
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