On December 19, the “Verification†column reported on the large-scale cultivation of genetically modified crops in the United States and the large consumption of genetically modified foods. But on the Internet, there are always disputes over genetic modification. Why develop GM crops? Is genetically modified food harmful to human health? Regarding related issues, a reporter from the “Proofing†section of the People’s Daily interviewed Chinese and foreign experts.
Why Develop Transgenic Technology
Huang Dazhao (researcher of the Institute of Biotechnology, Chinese Academy of Agricultural Sciences): Transgenic technology uses modern biotechnology to artificially isolate, modify, and transfer genes of interest to produce new varieties, thereby giving new traits to the original variety. For example, genetically modified herbicide-tolerant (glyphosate) soybeans save the labor and cost of weed control by increasing the tolerance to herbicides.
Bromwald (Professor of Cell Biology, Department of Cell Biology, Department of Botany, University of California, Davis): GM crops have two major benefits: First, they provide higher crop yields. The adverse effects of extreme weather and water shortages on global agriculture are becoming more and more serious, and the use of genetically modified technologies to cultivate new varieties can not only be resistant to insect pests and herbicides, but can even be resistant to drought, virtually expanding the area of ​​land that should be ploughed. Second, it effectively reduces the use of pesticides. According to statistics published by the British consulting firm PGEconomic, the use of genetically modified crops reduced the use of chemical pesticides by 438 million kilograms from 1996 to 2010.
Lin Min (Director, Institute of Biotechnology, Chinese Academy of Agricultural Sciences): The countries that plant genetically modified soybeans include the United States, Brazil, Argentina, Paraguay, Canada, Uruguay, South Africa, Mexico, Bolivia, Chile, and Costa Rica. In addition, many countries and regions have approved the import of genetically modified soybeans, including Australia, Canada, Japan, Switzerland, the United Kingdom, New Zealand, Russia, South Africa, Thailand, Turkey, Mexico, the United States, Colombia, the Philippines, China and Taiwan, the European Union. , Malaysia and so on. China's imports of genetically modified soybeans mainly come from the United States, Brazil and Argentina.
Duan Wude (Director of the Science and Technology Development Center of the Ministry of Agriculture): China has also carried out research on genetically modified soybeans. Significant progress has been made in the discovery of new soybean genes, the construction of transgenic technology platforms, and the selection of new varieties, but it is still under research. During the test phase, it was not planted.
Can Transgenes Affect Reproductive Ability?
Huang Kunlun (Professor, China Agricultural University): Since the introduction of genetically modified soybeans, research and development companies and many independent agencies around the world have conducted a large number of long-term food safety evaluations, including nutritional assessments, toxicological assessments, and allergenicity assessments. Tests have shown that the newly introduced protein does not increase the risk of toxicity, and consumption of genetically modified soybeans does not have an adverse effect on human health.
Take glyphosate-tolerant (SGT) genetically modified soybeans as an example. The gene transferred was phosphoenolpyruvylshikimate synthase (EPSPS) from Agrobacterium tumefaciens strain CP4, which conferred resistance to the herbicide glyphosate.
This protein gene is a restriction enzyme in plants and microorganisms. It is ubiquitous in human food and animal feed and has a long-term safe edible history. By homologous alignment of the protein with known toxin sequences in the database, no sequence homology was found. U.S., Japanese, and Korean scholars also used a simulated gastrointestinal fluid to digest the protein. The results showed that in the simulated gastric or intestinal fluid, the protein completely degraded within seconds. The mouse test of this protein showed that when the amount of gastric perfusion reached 572 mg/kg body weight, the protein did not produce adverse reactions to mice. It can be considered that the protein has little risk of toxicity to animals.
In addition, scientists from the United States, Japan, and China used genetically modified glyphosate-resistant soybeans and non-genetically modified soybeans to conduct a number of tests including sub-chronic toxicity and fecundity of animals. Among them, Japan used heated soy powder to feed rats and mice for 3 weeks at a dose of 30%, and examined general toxicity indicators and immunotoxicity indicators such as growth, food intake, organ weight, and organ biopsy. Soybeans are non-toxic to rats. In China, 91 days of feeding the rats with soy, the intake of food, body weight, blood biochemistry, blood routine, urine routine indicators and histopathological examination showed that the transgenic soybean did not produce sub-chronic toxicity to animals. In the United States, the reproductive ability test of 2-4 generations of breeding mice was carried out. The size, weight, testicular cell number and other indicators of the fetus were analyzed. The transgenic soybeans were considered to have no reproductive toxicity to mice.
Do foreign genes destroy food nutrients?
Huang Kunlun: The nutritional composition of genetically modified soybeans and non-transgenic control soybeans is essentially equivalent and can be properly digested and utilized. The United States had six locations in 1992, four locations in 1993, five locations in the EU in 2005, and three consecutive years in the United States and Canada in 2000, 2001, and 2002 for glyphosate resistant soybeans of various genetic backgrounds. Analysis of nutrients found that glyphosate-tolerant soybean and its parent soybean in major nutrients (moisture, ash, protein, fat, fiber, carbohydrates) and antinutritional factors (lectins, phytic acid, trypsin inhibitors), and The content of fatty acids and amino acids is quite similar, and all are within the natural variation provided by the reference. In addition, in 1992, the United States also analyzed major nutrients of processed soybean products such as roasted soybean meal, defatted soybean meal, protein extracts, and protein concentrates from soybeans harvested at six sites. The results showed that there was no significant difference in processing performance and nutrient composition. .
At the same time, rats and cows were fed with processed and unprocessed glyphosate-tolerant soybeans and non-transgenic control soybeans for 4 weeks, broiler chickens for 6 weeks, trout fish 10 weeks, and scabs 5 days, and growth indicators, feed conversion ratio, muscle and fat were measured. Composition (chicken), milk production and milk composition, rumen fermentation and nitrogen digestibility (bovine) and other nutritional indicators, the results show that transgenic and non-genetically modified soybeans have the same nutritional value for animals.
Can genetically modified foods cause genetic variation?
Yang Xiaoguang (researcher of the Chinese Center for Disease Control and Prevention): Natural foods eaten by humans contain various genes, and no horizontal gene transfer or cross-species transfer has been found. From a scientific point of view, there is no particular difference between genetically modified foods and other conventional foods. After the food enters the human body, it will be degraded into small molecules under the action of the digestive system. It will not enter the human tissues in the form of genes, and will not affect the genetic composition of human beings. Genetically modified foods cannot change human genetic properties.
The difference between transgenic and non-genetically modified foods is the transfer of specific proteins. As long as the protein is not a sensitizer and a toxin, it has no essential difference with the protein in the food. It can be digested and absorbed by the body and will not be stored in the body for a long time.
Peng Yufa (Researcher, Institute of Plant Protection, Chinese Academy of Agricultural Sciences): The same reason as eating genetically modified foods, animals eat genetically modified soy feed. Herbicide-tolerant genes and genetically modified proteins are also rapidly degraded and they are digested and absorbed as nutrients. Will not accumulate in the body.
Is genetically modified soybeans allergic to humans?
Huang Kunlun: The newly introduced protein in genetically modified soybeans does not increase the risk of sensitization, and genetic manipulation has not caused the increase in the type and content of allergens in soybean itself.
Common allergens are generally high levels of biological proteins, accounting for 1% - 80% of total protein. The CP4 EPSPS protein accounted for only 0.08% of the total protein in the transgenic soybean. The gene's donor soil Agrobacterium is not an allergen, and the protein can be rapidly digested in simulated gastric fluids. In addition, from 1995 to 2007, the serum of allergic children and adults in Europe, the United States, Japan, and South Korea, especially the serum of soybean allergy patients, was used to perform specific binding experiments with the CP4 EPSPS protein, indicating that the protein does not work with any Allergic serum binding. Experiments with rats also confirmed that the protein did not elicit an allergic reaction in animals, either by injection or by gavage.
Bloomwald: There is no basis for the claim that GM foods cause allergies in humans.
Can the long-term safety of genetically modified humans be guaranteed?
Yang Xiaoguang: The long-term health effects of genetically modified foods are one of the important issues in the evaluation of genetic safety. Before GM foods are brought to market, they must undergo strict food safety evaluation. This evaluation system is more rigorous and even harsh than traditional foods. This includes the evaluation of the long-term health effects of the human body. In the test process, an overconstant test was used, which is much more than the conventional food dose. The reason why the supernormal test is used is that the long-term effect is taken into consideration, and the scientific research model is equivalent to the long-term effect test. The current chemical foods and medicines are mostly verified using this system. For example, a 90-day feeding experiment in rats corresponds to 1â„8 of the rat's life cycle. The rat 2-year feeding test is a chronic toxicity test that observes its entire life cycle.
Bennett (Professor, University of California, Davis): People have concerns about the safety of genetically modified crops mainly because they do not understand it. They believe that genetically modified plants belong to unnatural breeding methods and have potential safety hazards. In fact, transgenes are only the selective introduction of genes. It is a developmental stage in the long history of human breeding.
Bloomwald: According to the information released by the US Department of Agriculture, the proportion of GM soybeans and genetically modified corn grown in the United States is above 90%. Since the commercial production of genetically modified soybeans in 1996, hundreds of millions of Americans have directly or indirectly consumed genetically modified soybeans for 16 years. To date, no confirmed genetically modified food safety accident has occurred.
Does the glyphosate-resistant crop cause weeds to spread?
Wu Kongming (an academician of the Chinese Academy of Engineering and the vice president of the Chinese Academy of Agricultural Sciences): As early as before the application of glyphosate-tolerant crops, there were reports of resistance to weeds. It has been found that most of the resistant weeds cannot hybridize with existing glyphosate-tolerant crops. Therefore, there is no evidence that the production of resistant weeds is directly related to the cultivation of glyphosate resistant crops. As with other organisms, long-term, large-scale exposure of weeds to certain herbicides does cause resistance to the herbicides, which is a common biological phenomenon.
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