Risks and Benefits
Research studies present conflicting arguments as to whether consuming GM crops is beneficial or harmful to human health. With every alleged GMO health risk, there are counterarguments either opposing health risk claims or suggesting GMOs provide more benefits than harm. The most notable GMO risks to humans are the potential development of allergens to GM related crops and toxicity from GM crops. However, studies also show GM crops have benefits including the increased nutritional value in foods.
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Allergens
An allergen is a type of antigen that sets off an abnormal vigorous immune response, triggering the immune system to fight off perceived threats that are harmless to the body. Barber Rodriguez and Salcedo (2008) are only some researches that have looked into the allergenic properties GM crops have and their impact on human health. Researchers outline multiple ways for an individual to develop allergies from consuming GM crops.
The first is due to transgene
genetic materials with inherent allergic properties. Transgene genetic materials present in GM crops are transferred into the human body through using a change in the gene expression. Changes in gene expression can encompass changes in storage tissue or in other parts of the plant. The interaction of the trangenetic material with the exposed population will determine the magnitude of the allergic reactions (or lack there of). Examples of GM crops that have transgenetic material include Bacillus thuringiensis (Bt) corn/maize, BT potato and soybean resistant to the herbicide glyphosate.
Newly expressed proteins from GM crops have the potential to sensitize the immune system to react abnormally to similar proteins due to cross-reactivity with another allergen to which individuals have already been sensitized. Allergopharma states "a cross-reactivity allergy is present when the antibodies against a specific allergen are also capable of identifying other allergens from other allergen sources and may thus induce an allergic reaction to those allergens as well. Cross-reactivity is usually due to the cross between pollen and foods. Some cross-reactive GM crops include soy, rice and tomato.
One other contributing factor for the increase incidences of allergens is the role of gene transfer(s). Gene transfer(s) can cause change in gene expression creating abnormal immune responses to perceived threats that were previously coded as harmless. Additionally, allergenic potential can directly be a result from new proteins or by interactions between new and usual proteins.
Example: Gene transfer of an allergen occurred in the 1996 transgenic soybeans case. The gene for a 2S albumin, a major group of seed storage protein, from the Brazil nut, a common allergen, was transferred to enhance the methionine content of animal feed. The introduction of allergenic proteins contained in the Brazil nut in soy products contributed to the increased sensitivity of soybean products for those already allergic to the nut protein.
While some studies state GMOs have negative effects on allergies, other studies cite potential benefits to GM crops consumption for individuals with allergies. Individuals with food allergies may profit from hypoallergenic novel foods through increased dietary variation and reduced restriction accompanying GM crops.
There are a few studies showing data supporting incidence of food allergens are increasing. There is no documented proof of commercially grown GM crops caused new allergies due to transgenically induced allergenic proteins or that generation of a GM crop causes biologically significant increases in endogenous allergenicity of a crop. All major genes used in GM crops indicated no allergenic potential.
Toxicity
GM crop studies found an association between tryptophan consumption, L-tryptophan specifically, and an increased number of deaths as well as neurologic disability. Tryptophan acted as the causal toxic agent. L-tryptophan is used plant proteins of crops such as GM maize and dietary supplements. The use of L-tryptophan was associated with an outbreak of eosinophilia-myalgia syndrome (EMS), a flu-like neurological condition. Large doses of tryptophan produced metabolites, which hindered normal degradation of histamine.
Example: Seralini and colleagues looked into the effects of R-tolerant GM maize in rodents. The study found life-long toxic effects. Tumors developed considerably faster in rodents with a diet of R-tolerant GM maize in comparison to control rodents.
Studies suggests that many traditional foods such as potatoes and beans are considered safe to consume, even if the food contains anti-nutrients, toxins and/or allergens. Furthermore, studies found no expected toxicities by the preparation of Bacillus thurngienses, a pesticide associated with increased allergen sensitivity.
Antibiotic Resistance
Antibiotic resistance is attributed to HGT. Antibiotics are used in early stages of genetic modification from HGT to eliminate chances of bacterial mutation and antibiotic resistant. A study done by Indiana State University and University of California San Diego found that hospitals observed decreased effectiveness of antibiotic drugs Hug (2008) found antibiotic resistance could be due to the HGT of GM crops via the transformation of bacteria in the food chain. Being exposed to the production or consumption GM crops can decrease antibiotic efficiency. Antibiotic markers persist in the body and can make antibiotic medications less effective. The amount of DNA experiencing HGTs is between 0.1 and 1g per day. About 20% of GM crops create new viral strains with unknown properties (positive or negative).
However, studies state the probability of transfer genesis is "infinitestimally" small. Antibiotic resistance is limited by the breakdown of DNA in the gut and food in the digestive process.
Additional Risks and Benefits
Producing and consuming GM crops is associated with increased endocrine disruption, reproductive disorders, and accelerated aging. There is evidence that the increased use of glyphospate-based herbicides on GM crops is linked to endocrine disruption. While not directly a result of the crop, it's a consequence of making the crops resistant to the herbicides. More research needs to be done over these potential risks.
GM crops also contributed to an increase in the number of functional foods or nutraceutical foods with added benefits. Nutraceutical is applied to isolated nutrients, dietary supplements and herbal products, specific diets, processed foods, and GM crops. Several nutraceutical foods include tomatoes, soybeans, and golden rice. Modified genes can be more specific and controlled to produce particular health advantages. Nutritionists expect higher nutrient content and an increased amount of nutrients (proteins, fatty acids, minerals, trace elements and vitamins) along with less anti-nutritional factors from GM crops.
Tomatoes are genetically modified with increased lycopene. Nutritionists suggested an association between increased consumption of lycopene and reduced risk of prostate cancer. However, the Food and Drug Administration concluded there is little scientific evidence to reliably back this claim. Studies associated soybean proteins with antihypertensive properties such as lowering blood pressure. Scientists claim Golden Rice contains more Vitamin A. Studies showed Golden Rice leads to decreased rates of childhood blindness due to the increased consumption of Vitamin A.
Capacity of Golden Rice lines with varying carotene content to supply the recommended nutrient intake of vitamin A. In rice-based societies,Golden Rice stands a very good chance of being able to deliver the recommended daily allowance of vitamin A (after conversion from β-carotene) to all children. The diagram (right) shows that even with a very low dietary intake of vitamin A from other sources (green), Golden Rice varieties with a low β-carotene content (orange) could fully provide the daily needs of these children. Varieties with higher β-carotene content would make sure that an even larger proportion of the population reached the recommended levels.
Genetically engineering crops have the potential to produce safer variation of crops, which could replace harmful traditional varieties by reducing the levels of undesired substances including mycotoxins, alkaloids and glucosinolates.
Proponents of GM crops state GM crops are cheaper to manufacture allowing a higher yield in food production. Increased crop yield could reduce global hunger by supplying more nutritious food to developing countries for distribution.