- What are Genetically Modified Organisms (GMOs) ?
- Genetically Modified Food Pros and Cons
- Food applications for GM plants
- Are GM foods safe to eat ?
- Glyphosate exposure, cardiovascular diseases and cancer risks
- Genetically modified food and potential to cause allergy
- Genetically Modified Food and Gene transfer studies in human volunteers
- Genetically Modified Foods on Human Health
What are Genetically Modified Organisms (GMOs) ?
According to a new United Nations Department of Economic and Social Affairs report – The World Population Prospects: The 2017 Revision – published on 21 June 2017, the current world population of 7.6 billion is expected to reach 8.6 billion in 2030, 9.8 billion in 2050 and 11.2 billion in 2100 1). By the time someone born today in the US reaches voting age, there are likely to be another one billion people. Most of those people will live in cities.
How will we produce enough nutritious food to support this burgeoning population and ensure access to food resources, particularly as climate change stresses the environment is an important question and how do we do that keeping an eye on safety, sustainability, affordability and equity ?
Genes change every day by natural mutation and recombination, creating new biological variations 2). Humans have been exploiting this for centuries—shuffling genes in increasingly systematic ways and using extensive crossing and artificial selection—to create many combinations that would never otherwise have occurred. Just about everything we eat is derived from livestock, crops, and micro-organisms bred specifically to provide food. Humans have also redistributed genes geographically: the soybean is native to Asia but is now grown throughout the Americas, and the potato, native to the American continent, is grown throughout the temperate world. DNA has never been “static,” neither naturally nor at the hand of people.
In 1946, scientists first discovered that DNA can be transferred between organisms 3). Genetic modification is an extension of this. Combining genes from different organisms is known as recombinant DNA technology and the resulting organism is said to be ‘Genetically modified (GM)’, ‘Genetically engineered’ or ‘Transgenic’ 4). Genetically modified organisms (GMOs) are plants, animals or microorganisms that have had their genetic material altered in the lab to create new varieties of plants, animals, and organisms with desired characteristics 5). GM products which are currently in the pipeline include medicines and vaccines, foods and food ingredients, feeds and fibres 6).
It is now known that there are several mechanisms for DNA transfer and that these occur in nature on a large scale, for example, it is a major mechanism for antibiotic resistance in pathogenic bacteria. However, unlike conventional breeding, in which new assortments of genes are created more or less at random, genetic modification allows specific genes to be identified, isolated, copied, and introduced into other organisms in much more direct and controlled ways. The principal transgenic crops grown commercially in field are herbicide and insecticide resistant soybeans, corn, cotton and canola. Other crops grown commercially and/or field-tested are sweet potato resistant to a virus that could destroy most of the African harvest, rice with increased iron and vitamins that may alleviate chronic malnutrition in Asian countries and a variety of plants that are able to survive weather extremes. There are bananas that produce human vaccines against infectious diseases such as hepatitis B, fish that mature more quickly, fruit and nut trees that yield years earlier and plants that produce new plastics with unique properties 7). For example:
- A wide range of crops resistant to pests, diseases, and herbicides.
- Food materials with improved keeping and processing qualities (such as fruit much less susceptible to mould spoilage) and reduced or eliminated natural toxicants (such as glycoalkaloids in potatoes) or allergens (such as allergenic proteins in nuts).
- Better understanding of responses of crops to environmental stress and development of varieties that can grow in areas currently too inhospitable.
- Production of high value drugs such as vaccines in high volume agricultural crops such as oilseed rape or livestock such as in milk of dairy cattle.
- Development of renewable and sustainable sources of new materials (such as plastics based on starch or vegetable oil) in designer agricultural crops such as oilseed rape, potato, and maize.
The most obvious difference from conventional breeding is that genetic modification allows us to transfer genes between species. For example, the gene for bovine chymosin has been transferred to industrial micro-organisms—Kluyveromyces lactis (a yeast), Aspergillus niger var awamori (a fungus), and Escherichia coli K12 (a bacterium). These microbes are grown in fermenters to produce chymosin (rennet) on a commercial scale; this rennet, which replaces the conventional form obtained from slaughtered animals, is now widely used in cheese production 8).
The first genetically modified (GM) plant was produced in 1983, using an antibiotic-resistant tobacco plant 9). China was the first country to commercialize a transgenic crop in the early 1990s with the introduction of virus resistant tobacco.
What is Genetically Modified Food
Genetically Modified Food (GMF) means any food containing or derived from a genetically engineered organism 10). The majority of the biotech-crops available on the global market have been genetically manipulated to express one of these basic traits: resistance to insects or viruses, tolerance to certain herbicides and nutritionally enhanced quality. There has been a 60-fold rise in the application of Agri-biotechnology since 1996, when the first biotech-crop was commercially produced 11). Advocates say that they have increased agricultural production by more than US$98 billion and saved an estimated 473 million kilograms of pesticides from being sprayed. But critics question their environmental, social and economic impacts 12). Major producers of GM crops include USA, Argentina, Canada, and China 13). In Canada Genetically Engineered (GE) ingredients are used in more than 70% of the processed food products 14). The current rate of biotech crop adoption is remarkably higher in developing versus industrialized countries (21% vs. 9%) 15). Developing countries are rapidly accepting the technology with the hope of alleviating hunger and poverty. These countries account for 40% of the global farmlands used for GM crop cultivation 16). It is predicted that, by 2015, more than 200 million hectares of lands will be planted by biotech crops in about 40 countries 17).
Most processed foods in the U.S. contain genetically engineered (GE) ingredients, since over 90 percent of the corn and 95 percent of the soybeans grown in this country in 2017 were genetically engineered 18). Even though you may not realize it, you are probably eating GMOs right now.
Fruits and vegetables
Papaya has been developed by genetic engineering which is ring spot virus resistant and thus enhancing the productivity. This was very much in need as in the early 1990s the Hawaii’s papaya industry was facing disaster because of the deadly papaya ring spot virus. Its single-handed savior was a breed engineered to be resistant to the virus. Without it, the state’s papaya industry would have collapsed. Today 80 % of Hawaiian papaya is genetically engineered, and till now no conventional or organic method is available to control ring spot virus 19).
The NewLeaf™ potato, a GM food developed using naturally-occurring bacteria found in the soil known as Bacillus thuringiensis (Bt), was made to provide in-plant protection from the yield-robbing Colorado potato beetle 20). This was brought to market by Monsanto in the late 1990s, developed for the fast food market. This was forced to withdraw from the market in 2001as the fast food retailers did not pick it up and thereby the food processors ran into export problems. Reports say that currently no transgenic potatoes are marketed for the purpose of human consumption. However, BASF, one of the leading suppliers of plant biotechnology solutions for agriculture requested for the approval for cultivation and marketing as a food and feed for its ‘Fortuna potato’. This GM potato was made resistant to late blight by adding two resistance genes, blb1 and blb2, which was originated from the Mexican wild potato Solanum bulbocastanum. As of 2005, about 13 % of the zucchini grown in the USA is genetically modified to resist three viruses; the zucchini is also grown in Canada 21).
Cooking oil, margarine and shortening may also be made from several crops. A large percentage of Canola produced in USA is GM and is mainly used to produce vegetable oil. Canola oil is the third most widely consumed vegetable oil in the world. The genetic modifications are made for providing resistance to herbicides viz. glyphosate or glufosinate and also for improving the oil composition. After removing oil from canola seed, which is ∼43 %, the meal has been used as high quality animal feed. Canola oil is a key ingredient in many foods and is sold directly to consumers as margarine or cooking oil. The oil has many non-food uses, which includes making lipsticks.
Maize, also called corn in the USA and cornmeal, which is ground and dried maize constitute a staple food in many regions of the world. Grown since 1997 in the USA and Canada, 86 % of the USA maize crop was genetically modified in 2010 22) and 32 % of the worldwide maize crop was GM in 2011 23). A good amount of the total maize harvested go for livestock feed including the distillers grains. The remaining has been used for ethanol and high fructose corn syrup production, export, and also used for other sweeteners, cornstarch, alcohol, human food or drink. Corn oil is sold directly as cooking oil and to make shortening and margarine, in addition to make vitamin carriers, as a source of lecithin, as an ingredient in prepared foods like mayonnaise, sauces and soups, and also to fry potato chips and French fries. Cottonseed oil is used as a salad and cooking oil, both domestically and industrially. Nearly 93 % of the cotton crop in USA is GM.
The USA imports 10 % of its sugar from other countries, while the remaining 90 % is extracted from domestically grown sugar beet and sugarcane. Out of the domestically grown sugar crops, half of the extracted sugar is derived from sugar beet, and the other half is from sugarcane. After deregulation in 2005, glyphosate-resistant sugar beet was extensively adopted in the USA. In USA 95 % of sugar beet acres were planted with glyphosate-resistant seed 24). Sugar beets that are herbicide-tolerant have been approved in Australia, Canada, Colombia, EU, Japan, Korea, Mexico, New Zealand, Philippines, Russian Federation, Singapore and USA. The food products of sugar beets are refined sugar and molasses. Pulp remaining from the refining process is used as animal feed. The sugar produced from GM sugar beets is highly refined and contains no DNA or protein—it is just sucrose, the same as sugar produced from non-GM sugar beets 25).
GMF found in most of processed foods 26) :
- Corn derived ingredients
Oil, starch, corn syrup, alcohol
- Soybean derived ingredients
Oil, soy flour, soy proteins, lecithin
- Canola oil
- Sugar from sugar beets
Papaya, squash, sweet corn
Indirect GMO foods 27)
Animals fed GMO grain
- Meat – beef, chicken, pork
- Milk, yogurt, cheese, butter
Foods made with any of the above
- Prepared meals
- Baked goods
Timeline of GMO being introduced into US Foods 28)
- 1992 – FDA policy
- 1994 – Tomato and squash
- 1996 – Corn, soybeans, canola
- 1998 – Papaya
- 2008 – Sugar beets
- 2011 – High-oleic soybeans
The United States Department of Agriculture (USDA) supports all methods of agriculture production, including organic, conventional, and biotechnology. Consumers purchase organic products expecting that they maintain their organic integrity from farm to market, and USDA is committed to meeting these expectations. No matter where it was grown, if a product has the USDA Organic label on it, it wasn’t produced with GMOs. To meet the USDA’s organic regulations, farmers and processors must show they aren’t using GMOs and that they are protecting their products from contact with prohibited substances from farm to table 29).
GMO crops on the US market in 2015 according to Whole Foods 30) :
- 94% of soybeans
- 93% of corn
- 96% of cotton
- Alfalfa, sugar beets, canola, papaya, sweet corn, zucchini, yellow squash
GMO crops on the US market in 2017 according to the United States Department of Agriculture 31)
Genetically engineered (GE) seed varieties were commercially introduced in 1996. Adoption rates for these crops increased rapidly in the years that followed. Currently, over 90 percent of U.S. corn, upland cotton, soybeans, canola, and sugarbeets are produced using genetically engineered varieties 32).
- Herbicide-tolerant (HT) crops, which tolerate potent herbicides (such as glyphosate or glufosinate), provide farmers with a broad variety of options for effective weed control. Based on USDA survey data, the percent of domestic soybean acres planted with HT seeds rose from 17 percent in 1997 to 68 percent in 2001, before plateauing at 94 percent in 2014. HT cotton acreage expanded from approximately 10 percent in 1997 to 56 percent in 2001, before reaching a high of 91 percent in 2014. Adoption rates for HT corn grew relatively slowly immediately following the commercialization of GE seeds. However, adoption rates increased following the turn of the century. Currently, approximately 89 percent of domestic corn acres are produced with HT seeds.
- Insect-resistant crops, which contain genes from the soil bacterium Bt (Bacillus thuringiensis) and produce insecticidal proteins, have been available for corn and cotton since 1996. Domestic Bt corn acreage grew from approximately 8 percent in 1997 to 19 percent in 2000, before climbing to 81 percent in 2015. Bt cotton acreage also expanded rapidly, from 15 percent of U.S. cotton acreage in 1997 to 37 percent in 2001. Currently, 85 percent of U.S. cotton acres are planted with genetically engineered, insect-resistant seeds. Increases in adoption rates for Bt corn may be due to the commercial introduction of new varieties resistant to the corn rootworm and the corn earworm (prior to 2003, Bt corn varieties only targeted the European corn borer). Adoption rates for Bt corn may fluctuate over time, depending on the severity of European corn borer and corn rootworm infestations. Similarly, adoption rates for Bt cotton may depend on the severity of tobacco budworm, bollworm, and pink bollworm infestations. As of 2017, insect-resistant varieties have not been commercialized for soybeans.
The figures below illustrate increases in adoption rates for “stacked” varieties, which have both (in some cases, multiple) HT and Bt traits. Adoption of stacked varieties has accelerated in recent years. Approximately 80 percent of cotton acres and 77 percent of corn acres were planted with stacked seeds in 2017.
Plants with favourable characteristics have been produced for thousands of years by conventional breeding methods. Desirable traits are selected, combined and propagated by repeated sexual crossings over numerous generations. Farmers have long sought to breed better plants. Traditionally this has involved repeatedly cross-pollinating plants to create an offspring with the desired combination of traits. This process introduces a number of genes into the plant, including some that may have unwanted traits. This is a long process, taking up to 15 years to produce new varieties.
The purpose of genetically altering, also called genetically engineering (GE), plants is to improve their durability, such as through drought tolerance or disease resistance, or their nutritional value. These changes are aimed at increasing yield and lowering costs. GMOs already play a role in feeding extra mouths, and if we let it, that role may grow. Yet they are also still a source of controversy, and there are both valid concerns and misconceptions.
In the developing world, 840 million people are chronically undernourished, surviving on fewer than 8000 kJ/day (2000 Kcal/day). Approximately 1.3 billion people are living on less than US$1/day and do not have secure access to food. Many of these are also rural farmers in developing countries, depending entirely on small-scale agriculture for their own subsistence and to make their living. They generally cannot afford to irrigate their crops or purchase herbicides or pesticides, leading to a vicious circle of poor crop growth, falling yields and pest susceptibility. At the same time, the Intergovernmental Panel on Climate Change predicts that changing weather patterns will almost certainly have a negative impact on crop yields.
In addition, earth’s population has more than doubled since 1960 and the world’s population is predicted to double again over the next 40 years, the UN estimates it will reach 9.8 billion by 2050, with over 95% of individuals being born in developing countries.
It is estimated that to meet these increased demands, crop demand is predicted to increase by 100 to 110 percent of 2005 levels over the same period with food production must increase by at least 40% in the face of decreasing fertile lands and water resources.
GM plant technologies are one of a number of different approaches that are being developed to combat these problems. Specifically, studies are under way to genetically modify plants to increase crop yields, or to directly improve nutritional content.
Genetic engineering isolates the gene for the desired trait, adds it to a single plant cell in a lab, and generates a new plant from that cell. By introducing only one gene, scientists hope to avoid transferring unwanted traits from other genes.
Furthermore, genetic engineering not only allows this process to be dramatically accelerated in a highly targeted manner by introducing a small number of genes, it can also overcome the barrier of sexual incompatibility between plant species and vastly increase the size of the available gene pool.
Mixing plant species is how we’ve gotten papayas free of viruses, corn plants that survive drought, soybeans that stand up to weed killer (e.g. Roundup), potatoes that don’t bruise, and crops that yield more and cost less. That’s good news for our food supply and the business of farming.
Now the emergence of the gene-editing tool CRISPR/Cas9 is making it possible to precisely edit the native DNA of organisms with the potential to dramatically increase crop yields. Unlike previous approaches to GM crops that introduce foreign DNA into an organism, genome editing achieves much the same outcome as selective breeding—but in a much faster and more selective way and without having to rely on natural genetic variation.
Can GMOs Be Used in Organic Products ?
The use of genetic engineering, or genetically modified organisms (GMOs), is prohibited in organic products. This means an organic farmer can’t plant GMO seeds, an organic cow can’t eat GMO alfalfa or corn, and an organic soup producer can’t use any GMO ingredients 36).
USDA (United States Department of Agriculture) supports all methods of agriculture production, including organic, conventional, and biotechnology. Consumers purchase organic products expecting that they maintain their organic integrity from farm to market, and USDA is committed to meeting these expectations. No matter where it was grown, if a product has the USDA Organic label on it, it wasn’t produced with GMOs. To meet the USDA’s organic regulations, farmers and processors must show they aren’t using GMOs and that they are protecting their products from contact with prohibited substances from farm to table 37).
In the sketch below 38), the organic farmer has set up several buffer zones to protect the integrity of her organic crops from GMOs. Where her farm borders the conventional farm, she has set aside an area which she will farm organically (for example, she won’t apply prohibited pesticides), but she won’t sell that land’s crops as organic. She has also posted “no spray” signs on the borders of her property and has another buffer zone on the left side to protect her farm from unintended substances from the local road. A final buffer zone on the right side of her property includes a row of trees to reduce erosion and protect runoff into the bordering river.
Figure 1. Farm Layout between Certified Organic Farm and Conventional Farm per United States Department of Agriculture 39)
Benefits from genetically GMO crops
GMO crops can confer social and environmental benefits 40):
- herbicide resistant crops need less tillage, which enhances the content of organic matter in the soil, reduces erosion by wind and water and improves soil structure. Less herbicide is used resulting in less runoff to watercourses.
- plants producing toxins selective against caterpillar larvae reduce the number of sprays of persistent chemicals by up to 60%. This spares useful insects and reduces the pollution of soil and waterways with chemicals.
- GMO crops can be made that produce vitamins lacking in some staple crops e.g. genes for vitamin A production introduced into rice 41).
- research is in progress to increase salt or drought tolerance – an important consideration as the world population rises and, currently, arable land is at a premium.
How different is food from GM crops as compared to food from non-GM crops ?
Changes to genes aren’t necessarily a bad thing. They happen in nature. In fact, no matter what’s on the menu, it isn’t exactly the same as what grew hundreds or thousands of years ago.
Bits of DNA, called genes, are responsible for all sorts of characteristics and traits in every living thing, from height to how certain cells work. Useful traits (genes) help the plants and animals with those genes survive or thrive better than ones without them, so they get passed along and eventually become common.
Humans have been “genetically modifying” plants and animals for thousands of years. Five hundred years ago, say a farmer noticed some corn was a little sweeter. To replicate that flavor, the farmer might select those seeds for the next crop. That new trait came about by random genetic mutation, and establishing a noticeably sweeter flavor using selective breeding would take years, if not decades.
Our ancestors sped up the process when they saved seeds of cream-of-the-crop plants to grow the next time, and the next, and the next. That’s what turned small bunches of tiny kernels on tall grass 10,000 years ago into the big ears of juicy corn on the cob we have today. With animals, picks of the litter were paired to breed “new-and-improved” babies.
Genetic engineering does much the same thing, discovering and introducing genes that yield desired traits, but in a faster and more accurate way than selective breeding.
Some GM foods, like BT (Bacillus thuringiensis) crops, are engineered to contain a form of pesticide, which means they don’t need to be sprayed with chemical pesticides. Bacillus thuringiensis (Bt) is a common bacteria that has played a very uncommon role in agriculture and the development of genetically modified foods. The natural insecticidal abilities of these bacteria have made them an important pest control tool for nearly a century. While their use as a natural bio-pesticide is widely accepted and approved for organic applications, the engineering of Bt genes into major crops has been more controversial. Eating food that produces a pesticide sounds scary, but as the video above notes, pesticide doesn’t always mean it is inedible or harmful to humans. Many substances harm insects or animals, but not humans—coffee is one example.
And there are examples of pesticide-resistant GMOs having a tangible positive impact on people. When eggplant farmers in Bangladesh began to get sick from using too much chemical pesticide, for example, they implemented BT and were able to reduce pesticide use by 80 percent.
Some GMOs are specially made to be packed with extra vitamins, minerals, and other health benefits. For example, Swiss researchers created a strain of “golden” rice with a lot of beta-carotene, an antioxidant good for your eyes and skin. Soybeans whose fats have been changed so they’re more like olive oil can be turned into a heart-healthy replacement for oils with trans fats that’s more heat-tolerant and better for cooking. And those bruise-free potatoes are supposed to cut down on cancer-causing chemicals created when spuds become french fries.
Much of the backlash against GMOs is less about genetic engineering and more about the business practices of the corporations that control our food supply. GMO crops have been a money-maker for herbicide companies and as crops have been modified to be herbicide-resistant, herbicide use increases. For companies making GMO seeds and associated herbicides, that’s a lot of power over something as critical as how we feed ourselves.
As the population grows, it’s going to get harder to feed everyone. The Food and Agriculture Organization of the United Nations (FAO) estimates food production will need to double in some parts of the world by 2050. GMOs are one way to make enough nutritious food available with limited land, water, and other resources.
And perhaps we need to be particularly careful when it comes to genetically modified anything, to thoroughly vet it for harm to humans and ecosystems. Once the genie’s out of the bottle, many worry we might not be able to get it back in again.
Genetically Modified Food Pros and Cons
Currently with over 20 years of exposure to genetically modified foods, there is no substantiated allergenicity (that causes an allergy) in humans to genetically modified food or food ingredient 42).
Livestock data 43)
- 100 billion animals fed GMO grain between 2000-2011
- No difference in health outcomes comparing before after GMO introduction
- No difference in nutrient or food composition
Safety studies in animals 44)
- Native plant DNA-fragments may be absorbed with very low frequency
- Assume same for recombinant DNA
- No transfer of recombinant DNA from feed to animal tissues (eggs, meat or milk)
Gut microbiota 45)
- Horizontal gene flow
- DNA rapidly degraded by digestion
- Limited amount may escape to colon
- Native and recombinant DNA similar
- Transformation of gut microbiota highly unlikely
According to this study paper 46) that focuses on (1) the potential of transgenes (genetic engineering) to alter genes stability and (2) the potential risks to food and feed safety associated with genome instability (refers to a high frequency of mutations within the genome of a cellular lineage. These mutations can include changes in nucleic acid sequences, chromosomal rearrangements or aneuploidy). The authors found neither changes in gene expression nor mutations in amino acid sequences are likely to alter the safety of a protein or lead to the production of novel metabolites. Thus far, there is no evidence that a random genomic change in a crop has ever resulted in a novel safety issue, even when new alleles or genes were created. Therefore, other than changes due to the transgene products, the risks of introducing new food hazards are no different from the risks associated with traditional breeding 47).
The weight of the evidence leads to the conclusion that enhanced genetic instability from a transgene or from common sequences in two or more transgenes is unlikely 48). Even then, the probability that any genetic instability will lead to an altered protein or metabolic product that creates a biosafety issue is exceedingly small; the production of a GE stack does not measurably increase this probability. There is no readily identifiable biological reason why genomic changes occurring in the breeding of a GE stack would be different in nature, scale, or frequency from those taking place in non-genetically engineered crops or in genetically engineered crops with a single event.
The likelihood that any one mutation would create a biosafety issue is improbably small and would occur in a single plant in a field containing hundreds to millions of other plants. Thus, any negative consequences from that one mutation would be limited to seeds produced by that one plant, with dilution upon harvest minimizing the likelihood of any deleterious effects resulting from consumption. This large dilution factor helps explain why such changes, which may in principle lead to a negative effect, remain undetected and why breeding is generally considered a safe process 49).
Food applications for GM plants
Genetically modified crops have the potential to eliminate hunger and starvation in millions of people, especially in developing countries because the genetic modification can produce large amounts of foods that are more nutritious. Large quantities are produced because genetically modified crops are more resistant to pests and drought. They also contain greater amounts of nutrients, such as proteins and vitamins 50).
However, there are concerns about the safety of genetically modified crops. The concerns are that they may contain allergenic substances due to introduction of new genes into crops. Another concern is that genetic engineering often involves the use of antibiotic-resistance genes as “selectable markers” and this could lead to production of antibiotic-resistant bacterial strains that are resistant to available antibiotics. This would create a serious public health problem. The genetically modified crops might contain other toxic substances (such as enhanced amounts of heavy metals) and the crops might not be “substantially equivalent” in genome, proteome, and metabolome compared with unmodified crops. Another concern is that genetically modified crops may be less nutritious; for example, they might contain lower amounts of phytoestrogens, which protect against heart disease and cancer. The review of available literature 51) indicates that the genetically modified crops available in the market that are intended for human consumption are generally safe; their consumption is not associated with serious health problems.
To many, an organic diet has never been more in style than it is right now, with millions of consumers willing to shell out extra dollars for organic foods. Most of us have a vague idea that organic is better because it’s more natural and free of genetically modified organisms (GMOs) and pesticides. But have shoppers ever stop to wonder whether organic foods have as much of an impact on their health as they do on my wallet ?
Health experts and consumers have long debated whether organic foods are more nutritious and safer than conventional foods.
A study released in the Annals of Internal Medicine finds that organics do have some safety advantages over conventional foods, nutritionally speaking they have little extra to offer. The Conclusion: “The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods. Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.”
But what does “natural” even mean ? The line is harder to draw than we may think.
Genetically Modified Foods Role Increasing Food Production
In the developing world, 840 million people are chronically undernourished, surviving on fewer than 8000 kJ/day (2000 Kcal/day) 52), 53). Approximately 1.3 billion people are living on less than US$1/day 54), 55) and do not have secure access to food. Many of these are also rural farmers in developing countries, depending entirely on small-scale agriculture for their own subsistence and to make their living 56). They generally cannot afford to irrigate their crops or purchase herbicides or pesticides, leading to a vicious circle of poor crop growth, falling yields and pest susceptibility 57). In addition, the world’s population is predicted to double over the next 40 years, with over 95% of individuals being born in developing countries 58). It is estimated that to meet these increased demands, food production must increase by at least 40% in the face of decreasing fertile lands and water resources 59), 60). GM plant technologies are one of a number of different approaches that are being developed to combat these problems. Specifically, studies are under way to genetically modify plants to increase crop yields, or to directly improve nutritional content.
Crop yields worldwide are significantly reduced by the action of pathogens, parasites and herbivorous insects 61). Two examples of commercial GM crop growth in this area are the insect-resistant crops expressing the bt gene (from the bacterium Bacillus thuringiensis) and virus-resistant GM papaya 62). The first of these has been particularly successful; in the USA, for example, insect resistant GM maize is grown over an area of 10.6 million hectares and comprises 35% of all maize (GM and non-GM) grown in the country 63). At the laboratory level, resistance has also been engineered to bacterial and fungal plant pathogens.
A primary cause of plant loss worldwide is abiotic stress, particularly salinity, drought, and temperature extremes 64). In the future, these losses will increase as water resources decline and desertification intensifies. Drought and salinity are expected to cause serious salinization of all arable lands by 2050 65), requiring the implementation of new technologies to ensure crop survival. Although a number of promising targets have been identified in the production of abiotic stress tolerant GM plants, research remains at the laboratory-based level. An example is the study by Shou et al. 66) demonstrating that expression of an enzyme in GM maize activates an oxidative signal cascade that confers cold, heat and salinity tolerance.
Genetically Modified Foods Role in Increasing Nutritional Content
In the developed world the nutritional content of food items is not of major concern, as individuals have access to a wide variety of foods that will meet all of their nutritional needs. In the developing world, however, this is often not the case, with people often relying on a single staple food crop for their energy intake 67). GM technology offers a way to alleviate some of these problems by engineering plants to express additional products that can combat malnutrition. An important example of the potential of this technology is the ‘Golden Rice Project’. Vitamin A deficiency is widespread in the developing world and is estimated to account for the deaths of approximately 2 million children per year 68). In surviving children it has been identified as the leading cause of blindness 69). Humans can synthesize vitamin A from its precursor β-carotene, which is commonly found in many plants but not in cereal grains. The strategy of the Golden Rice Project was to introduce the correct metabolic steps into rice endosperm to allow β-carotene synthesis. In 2000, Ye et al. 70) engineered rice that contained moderate levels of β-carotene and since then researchers have produced the much higher yielding ‘Golden Rice 2’ 71). It is estimated that 72 g of dry Golden Rice 2 will provide 50% of the RDA of vitamin A for a 1–3-year-old child 72).
Golden Rice was developed for farmers in the poorest countries, and from the beginning, the aim of the scientists was to provide the technology free of charge, which required the negotiation of more than 100 intellectual and technical property licenses 73). Golden Rice will be given to subsistence farmers with no additional conditions and is an impressive example of a health solution that can be offered by plant biotechnology.
Are GM foods safe to eat ?
GM crops are tightly regulated by several government bodies. The European Food Safety Authority and each individual member state have detailed the requirements for a full risk assessment of GM plants and derived food and feed 74). In the USA, the Food and Drug Agency, the Environmental Protection Agency and the US Department of Agriculture, Animal and Plant Health Inspection Service are all involved in the regulatory process for GM crop approval 75). Consequently, GM plants undergo extensive safety testing prior to commercialization (for an example see http://www.efsa.europa.eu/en/topics/topic/genetically-modified-organisms).
Foods derived from GM crops have been consumed by hundreds of millions of people across the world for more than 15 years, with no reported ill effects (or legal cases related to human health), despite many of the consumers coming from that most litigious of countries, the USA.
There is little documented evidence that GM crops are potentially toxic.
This question should be better re-worded to not about the safety of eating the genetically modified foods, instead it should be – Is it safe to eat GMOs that have some herbicide and pesticide residue, even though based on theoretical considerations and in general, pesticide (specifically glyphosate) and herbicide levels in both organic and non-organic foods were within allowable safety limits.
Glyphosate exposure, cardiovascular diseases and cancer risks
Glyphosate ([N-(phosphonomethyl)glycine]) is a broad-spectrum herbicide discovered by John E. Franz from Monsanto and first sold in 1974 76). Glyphosate selectively inhibits the enzyme 5-enolpyruvyl-shikimate-3-phosphate synthase thereby blocking the shikimate pathway, a metabolic route not found in animals that is used by plants, bacteria, fungi, and algae to synthesize aromatic amino acids (tyrosine, phenylalanine, and tryptophan) 77). Due to its unique mode of action and an apparent selective toxicity to plants, glyphosate has become the dominant herbicide worldwide. Perhaps the most important aspect of the success of glyphosate has been the introduction of transgenic, glyphosate-resistant crops in 1996. Almost 90% of all transgenic crops grown worldwide are glyphosate resistant, and the adoption of these crops is increasing at a steady pace 78). As far as acute toxicity to vertebrates and environmental impact are concerned, glyphosate seems to compare favorably with many other herbicides (e.g., 2-4 D, paraquat, atrazine) 79).
However, as far as human health risks are concerned, it has become one of the most controversial pesticides. In the last years, however, this “once-in-a-century” herbicide has become one of, if not the most controversial pesticide. A few years ago, a report by Paganelli et al. 80) on glyphosate-based herbicides induced malformations in frog and chicken embryos, and anecdotal reports saying that there was an increased incidence of birth defects in South America genetically-modified-soy crop areas where glyphosate is extensively used, raising concerns on a possible teratogenicity of this herbicide 81), 82), 83). Experimental studies in mammals and epidemiology investigations, however, do not support the notion that exposure to glyphosate during pregnancy poses teratogenic risks to the unborn child 84), 85), 86). In the last two years, a possible excess of risk of cancer associated to glyphosate has taken center stage regarding to health hazards posed by widespread use of pesticides 87). A recent report by Pan et al. 88) suggesting that glyphosate might be a risk factor for coronary disease seems to open a new chapter in the ongoing debate on glyphosate safety. The lack of quantitative assessments of exposure (e.g., by repeated measures of urinary levels of glyphosate) and the fact that studies were not designed to find out dose-response relationships are two of the major weaknesses common to all epidemiology investigations of health hazards posed by glyphosate exposure 89). Owing to these methodological limitations, current epidemiology evidence is insufficient to conclude that exposure to glyphosate increases the risk of cardiovascular disease and or non-Hodgkin lymphoma, or any other type of cancer 90).
Glyphosate and cardiovascular diseases
A prospective cohort (2 years) study by Pan et al. 91), in Chinese pesticide factory workers, found associations between coronary artery disease and glyphosate exposure, overweight or body mass index ≥24 kg/m2, hyperlipidemia and alcohol use. It is of note that overweight, hyperlipidemia, and alcohol abuse are known and independent risk factors for coronary artery disease. No association between coronary artery disease and other known risk factors for coronary artery disease such as diabetes and smoking was found in this group of workers 92). The authors also measured workers’ plasma levels of glyphosate (11.73 µg/L) and its breakdown product aminomethylphosphonic acid—AMPA (5.29 µg/L). Nonetheless, all comparisons were made between a group of exposed workers (directly involved in glyphosate production lines) and a control group of theoretically unexposed workers who were not directly involved in the manufacture of glyphosate 93). It is unclear why the authors did not take advantage of the plasma levels of glyphosate to distinguish between exposed and non-exposed workers, and/or to analyze the data according to exposure level strata. Needless to comment, both groups are exposed to glyphosate (and AMPA) residues via food intake and this dietary exposure is a major contributor to chronic exposures and thus may be particularly relevant for the development of coronary artery disease. As commented elsewhere (studies on cancer risks), lack of a quantitative and reliable assessment of exposure is a major shortcoming of most epidemiology studies that have investigated associations between glyphosate and adverse health outcomes. Another major weakness of Pan et al.’s study is the relatively short duration of the prospective cohort (2 years) to make any inference on cause-and-effect relationships, i.e., between glyphosate and chronic diseases. Risk factors for the development of chronic and progressive diseases such as coronary artery disease probably act much earlier in the individual life history than the preceding two years followed by this cohort study.
At any rate, Pan et al.’s article 94) is the first report suggesting that exposure to glyphosate might be a risk factor for coronary heart diseases. Previous studies on cardiovascular toxicity of glyphosate-based herbicides described short term effects on the heart, such as arrhythmias and QTc prolongation, in cases of intentional (suicide attempts) or accidental poisoning with formulated products 95), 96), 97). Experimental studies and clinical reports, however, demonstrated that pulmonary and cardiac effects seen in acute intoxication result from ingredients of formulated products other than glyphosate (i.e., the surfactant polyoxyethylene amine—POEA used in most glyphosate-based herbicide formulations) 98), 99).
An apparent increase in rabbit heart defects after exposure to glyphosate during pregnancy was not confirmed by most experimental studies, nor was it revealed by epidemiology investigations 100), 101), 102).
Glyphosate and cancer risks
In March 2015, International Agency for Research on Cancer (IARC-WHO) is the specialized cancer agency of the World Health Organization, put glyphosate into category 2A (“probably carcinogenic in humans”), a classification that considerably fueled the debate over health risks associated with exposures to this widely used herbicide 103). The allocation of a compound into 2A category means that there is “limited” evidence in humans and “sufficient” evidence of carcinogenicity in animals. In this case, “limited” human evidence refers to a report on the excess of risk of non-Hodgkin lymphoma among exposed workers found by a meta-analysis of case-control studies by Schinasi and Leon  104). A systematic review and meta-analysis by Chang and Delzell  examined associations between glyphosate exposure and lymphohematopoietic cancers including NHL, multiple myeloma and leukemia 105). Similarly to the previous meta-analysis, Chang and Delzell also found a weak, albeit marginally significant association of glyphosate with non-Hodgkin lymphoma and a causal relationship has not been established between glyphosate exposure and risk of any type of lymphohematopoietic cancers 106).
Classification of glyphosate as a probable human carcinogen is at variance with previous evaluations by USEPA and the European Union and a more recent assessment by the EFSA (European Food Safety Authority). The European Food Safety Authority (EFSA) is the primary agency of the European Union for risk assessments regarding food safety 107). In October 2015, EFSA arrived at the conclusion that glyphosate is “unlikely to pose a carcinogenic hazard to humans and the evidence does not support classification with regard to its carcinogenic potential” 108), 109). In May 2016, a Joint Meeting of the Food and Agriculture Organization of the United Nations (FAO) Panel of Experts on Pesticide Residues in Food and the Environment and the World Health Organization (WHO) Core Assessment Group on Pesticide Residues (JMPR) was held at WHO Headquarters, Geneva (Switzerland), from 9 to 13 May 2016 110). The Joint FAO/WHO Meeting on Pesticide residues noted “Overall, there is some evidence of a positive association between glyphosate exposure and risk of NHL (non-Hodgkin lymphoma) from the case–control studies and the overall meta-analysis. However, it is it is notable that the only large cohort study of high quality found no evidence of an association at any exposure level. Glyphosate has been extensively tested for genotoxic effects using a variety of tests in a wide range of organisms. The overall weight of evidence indicates that administration of glyphosate and its formulation products at doses as high as 2000 mg/kg body weight by the oral route, the route most relevant to human dietary exposure, was not associated with genotoxic effects in an overwhelming majority of studies conducted in mammals, a model considered to be appropriate for assessing genotoxic risks to humans. The Meeting concluded that glyphosate is unlikely to be genotoxic at anticipated dietary exposures. In view of the absence of carcinogenic potential in rodents at human-relevant doses and the absence of genotoxicity by the oral route in mammals, and considering the epidemiological evidence from occupational exposures, the Meeting concluded that glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet 111).
To get a copy of the full report by the FAO-WHO Panel of experts report on Pesticide Residues in Food go here 112) : http://www.fao.org/fileadmin/templates/agphome/documents/Pests_Pesticides/JMPR/Report2016/JMPR_2016_Report_full.pdf
Whether or not causality is the most likely explanation for an observed association is a central issue whenever epidemiology findings have the potential to trigger public health interventions.
Greim et al. 113) in a review of 14 carcinogenicity data and studies (nine rat and five mouse) submitted to regulatory agencies on the carcinogenic potential of the herbicide glyphosate, found no evidence of a carcinogenic effect related to glyphosate treatment. The study authors concluded that glyphosate does not present concern with respect to carcinogenic potential in humans 114).
Genetically modified food and potential to cause allergy
Potential allergenicity (potential to cause allergy) to the novel gene product is another commonly expressed concern. Allergies to non-GM foods such as soft fleshed fruit, potatoes and soy are widespread. Clearly, new varieties of crops produced by either GM techniques or conventional breeding both have the potential to be allergenic 115). Concern surrounding this topic relates to two factors; the possibility that genes from known allergens may be inserted into crops not typically associated with allergenicity and the possibility of creating new, unknown allergens by either inserting novel genes into crops or changing the expression of endogenous proteins. Assessment of the allergenic potential of compounds is problematic and a number of different bodies have produced guidelines and decision trees to experimentally evaluate allergenic potential 116), 117), 118). These are effective at assessing compounds which may prove to be hazardous through a hierarchical approach which includes determining whether the source of the introduced gene is from an allergenic plant, whether GM foods react with antibodies in the sera of patients with known allergies and whether the product encoded by the new gene has similar properties to known allergens. In addition, animal models are used to screen GM foods 119). Tests are not performed to formally assess any risk posed by inhalation of pollens and dusts; however, this is not assessed for conventionally grown foods and feeds either, and no allergies have been attributed to commercially grown GM pollen to date.
Two examples are frequently quoted regarding GM crop allergenicity:
- A project to develop genetically modified peas by adding a protein from beans that conferred resistance to weevils was abandoned after it was shown that the GM peas caused a lung allergy in mice 120)
- Soya bean engineered to express a Brazil nut protein was withdrawn from production after it was also found to be allergenic in tests 121)
Opponents of GM technology often cite these examples as proof that it is inherently unpredictable and dangerous, although another interpretation would be to say that safety testing of GM plants was effective in both cases, having identified allergenic potential before either product was released to market. Moreover, GM technology might also be used to decrease the levels of allergens present in plants by reducing expression levels of the relevant genes. For example, research was recently undertaken to identify an allergen in soybeans and remove it using GM technology 122).
Genetically Modified Food and Gene transfer studies in human volunteers
There has only been one human feeding study conducted on the effects of GM foods. The study involved seven human volunteers who previously had their large intestines removed for medical reasons. These volunteers were provided with GM soy to eat to see if the DNA of the GM soy transferred to the bacteria that naturally lives in the human gut. Researchers identified that three of the seven volunteers had transgenes from GM soya transferred into the bacteria living in their gut before the start of the feeding experiment. As this low-frequency transfer did not increase after the consumption of GM soy, the researchers concluded that gene transfer did not occur during the experiment. In volunteers with complete digestive tracts, the transgene did not survive passage through intact gastrointestinal tract 123). Two studies on the possible effects of giving GM feed to animals found that there were no significant differences in the safety and nutritional value of feed stuffs containing material derived from GM plants 124), 125). Specifically, the studies noted that no residues of recombinant DNA or novel proteins have been found in any organ or tissue samples obtained from animals fed with GM plants 126), 127).
Genetically Modified Foods on Human Health
Genetically modified foods consumption began 20 years ago:
- No documented evidence for health risks
- Exposure rate is low
- Processing of grains
- Extraction of ingredients
- Heat treatment
- Low relative component of food
Looking at the cancer rates for both males and females in the United Stattes in 1999 and 2014, you can see cancer rates have actually fallen 128).
(Source U.S. Cancer Statistics Working Group. United States Cancer Statistics: 1999-2014 Incidence and Mortality Web-based Report. 129)).
(Source U.S. Cancer Statistics Working Group. United States Cancer Statistics: 1999-2014 Incidence and Mortality Web-based Report. 130)).
Snell et al. 131) examined 12 long-term studies (of more than 90 days, up to 2 years in duration) and 12 multigenerational studies (from 2 to 5 generations) on the effects of diets containing GM maize, potato, soybean, rice, or triticale on animal health. They referenced the 90-day studies on GM feed for which long-term or multigenerational study data were available. Many parameters have been examined using biochemical analyses, histological examination of specific organs, hematology and the detection of transgenic DNA. Results from all the 24 studies do not suggest any health hazards and, in general, there were no statistically significant differences within parameters observed.
The GM foods have the potential to solve many of the world’s hunger and malnutrition problems, and to help protect and preserve the environment by increasing yield and reducing reliance upon synthetic pesticides and herbicides. The debate on the safety of genetically modified organisms (GMOs) used for food and feed is still very lively throughout the world, more than 15 years after their first commercial release. There are controversies around GM food on several levels, including whether food produced with it is safe, whether it should be labelled and if so how, whether agricultural biotechnology and it is needed to address world hunger now or in the future, and more specifically with respect to intellectual property and market dynamics, environmental effects of GM crops and GM crops’ role in industrial agricultural more generally.
Review of literature found no plausible mechanism by which glyphosate would induce adverse developmental or reproductive outcome.
Almost all GMOs disseminated in the environment are plants, namely soy, maize, cotton, and oilseed rape (1995-2010) and more recently in November 2015, the U.S. Food and Drug Administration (FDA) after several years of study approved genetically modified (GM) faster-growing salmon as safe for human consumption 132). This is the first genetically modified animal to gain FDA approval and will probably be the first animal GMO in the supermarket 133). The faster growing salmon is a product of AquaBounty Technologies and was created by inserting a growth hormone gene from Chinook salmon and a promoter gene from Ocean Pout into the Atlantic salmon’s genome. Plainly stated, the promoter gene of the Ocean Pout turns on the growth gene from the Chinook salmon, allowing the fish to grow to market size in half the time as its non-GM counterpart (18 months vs. 3 years) 134). According to the FDA, since GM salmon was determined to be safe to eat and nutritionally equivalent to its non-GM counterpart, it does not require additional labeling identifying it as genetically modified 135), 136).
Apart from the faster-growing salmon, the plants, their genetic and phenotypic modifications are only herbicide tolerance and / or insecticide production (modified Bt toxins) in more than 99% cases. As a matter of fact, 97% of edible GMOs among cultivated GMOs (soy, corn and oilseed rape or canola, excluding cotton) are grown in South and North America – all these plants have been modified to tolerate and/or produce one or more pesticides and contain therefore such residues at various levels. Most are Roundup residues (it is a major herbicide used worldwide and tolerated by about 80% of GMOs). Other residues are from modified Bt insecticide toxins, which are directly synthesized by the GM plants from transgenes.
Current epidemiological evidence, albeit limited to a few studies using non-quantitative and indirect estimates and dichotomous analysis of exposures, does not lend support to public concerns that glyphosate-based pesticides might pose developmental risks to the unborn child 137). Nonetheless, owing to methodological limitations of existing analytical observational studies, and particularly to a lack of a direct measurement (urine and/or blood levels), or an indirect estimation of exposure that has proven valid, these negative findings cannot be taken as definitive evidence that glyphosate, at current levels of occupational and environmental exposures, brings no risk for human development and reproduction 138). Furthermore, because of potential for exposure of a large segment of human population to genetically modified foods, more research is needed to ensure that the genetically modified foods are safe for human consumption.
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