Fang Zhouzi
Aesthetician, Ph.D. in Biochemistry
"Great debate in science - Is GM crop safe? After the publication of the "Reporter's edition of the newspaper's March edition", some readers raised different opinions, which made me feel that it is necessary to clarify some of the misunderstandings and misinterpretations of the genetically modified foods that are circulating in the media and on the Internet.
A common question about the insect-resistant genetically modified rice that has just received a safety certificate in China is: “Doesn't eat insects, can people eat it?†Even a well-known hybrid rice breeding expert expressed such concern. It is recommended that you first This was a two-generation human trial and stated that he was willing to be the first volunteer tester.
In fact, this worry is redundant. The type of biotoxin (Bt protein for short) that is used in insect-resistant transgenic rice is actually non-toxic. It can only be processed into toxic proteins in the alkaline environment of insects, and the toxin protein must be on the surface of insect intestinal cells. Receptors combine to poison insects.
However, this situation cannot happen to people. There are several reasons for this. We usually eat food when it is heated and boiled. Bt protein is a kind of protein, and protein will denature when heated. Experiments show that Bt protein will lose its activity when boiled in water of 60 degrees Celsius for 1 minute. Even if it is eaten raw, it doesn’t matter. The Bt protein can only be processed into toxic proteins in the alkaline environment of the insect’s intestine. The human’s stomach environment is acidic, and human intestinal cell surfaces do not contain toxin protein receptors. Therefore, it will not poison. The Bt protein eaten by humans will be digested and broken down like other proteins.
In the United States, Bt protein has been used as a biopesticide for decades. It has been more than 10 years since planting insect-resistant transgenic crops containing the Bt gene in large areas. To date, no case of human or animal poisoning has been found. Experiments with rats and sheep also showed that eating Bt protein does not affect the health of mammals. In addition, the Bt protein, which has been approved for this pest-resistant transgenic rice, is mainly found in stems and leaves, and is almost absent in the endosperm (part of human food). Even if there is doubt about the safety of Bt protein, it can be safely consumed.
As for the requirement that genetically modified foods be tested as humans as drugs, and even listed in human trials for several decades, this is not feasible. Because foods and drugs are different, we have to eat a large variety of foods on various occasions every day. It is impossible to strictly control the food intake of the testers for a long period of time, and it is impossible for them to have clear indicators. Therefore, it is impossible to test the safety of certain foods like testing a specific medicine on the patient. No country requires food testing before going on the market. A more reasonable requirement is to conduct biochemical tests and animal experiments to evaluate its safety. Before genetically modified foods were listed on the market, they were required to do these tests. On the contrary, non-genetically modified foods such as hybrid rice were often marketed without safety testing. In this sense, GM foods are also safer than non-GM foods.
When the domestic media reported that the transgenic rice for pest resistance had obtained a safety certificate, it was often referred to as “the first time in the world that commercialized planting of genetically modified staple foodsâ€. This statement is very inaccurate. First of all, after obtaining the safety certificate, it is necessary to go through the stages of species approval to obtain commercial planting. Secondly, the three staple foods—maize (1934, 2.00, 0.10%), wheat (2281, 1.00, 0.04%), and rice—have received safety certificates in the United States. There are two types of commercial cultivation: The large-scale cultivation of genetically modified corn in the United States has a history of 14 years. More than 80% of corn in the United States is genetically modified corn. The United States has approved the commercial cultivation of six transgenic rice. Only GM wheat has not been planted in the United States after obtaining a safety certificate, not because the U.S. government does not approve it, but because existing herbicide-resistant and insect-resistant GM wheats do not have much advantages (for wheat, weeds and Insect pests are not a big problem, and the main factors affecting wheat production are diseases, droughts, and cold.) Monsanto R&D on it has withdrawn its own planting applications and is committed to research and development of genetically modified wheat with greater advantages such as disease resistance and drought resistance. .
Others said that genetically modified corn grown in the United States is used as feed and not for human consumption. This is also a rumor. Most of the genetically modified corn varieties approved for listing in the United States have been approved by the U.S. Food and Drug Administration for approval on the basis of standards that allow people to eat safely, and are used in large quantities to produce cornmeal, corn flakes, and thousands of foods. Only one pest-resistant GM corn is not easily digested due to the production of insect-resistant proteins. As a matter of prudence, U.S. regulatory authorities have stipulated that it can only be used as feed (other pest-resistant transgenic maize can be used for human consumption). In 2000, it was discovered that it was used by fast food shops to make corn chips and fried corn rolls, which caused nationwide recycling. Businesses suffered heavy losses and were once sensational. 28 people claimed to have eaten this GM food allergic reaction. However, the U.S. Centers for Disease Control has conducted blood tests on these people, claiming that their claims have no evidence. A placebo-controlled, double-blind trial of the claimant also denied that the genetically modified food can cause allergies. In other words, even genetically modified varieties that are approved for use as feed only are actually harmless to the human body. GM foods have been eaten by billions of people globally for more than ten years and no cases of allergies or other adverse reactions have been found.
The main purpose of promoting insect-resistant transgenic crops is to reduce the use of insecticides in large amounts, thereby reducing the pollution of pesticides to the environment and pesticide residues in foods. Some people argued that the "US Department of Agriculture" data shows that planting GM crops has increased the use of pesticides. In fact, they quoted data from a report released by the Organic Food Center, a non-governmental organization that advocates biotechnology and organic food promotion, in November 2009. It also refers to the increase in herbicides for herbicide-tolerant GM crops. The amount of agent. Even the report released by people opposed to genetic modification had to admit that from 1996 to 2008, the United States had reduced the use of pesticides by 64 million pounds due to planting insect-resistant GM crops.
The report's conclusion that “planting of herbicide-resistant GM crops increases the use of herbicides†is also considered as an erroneous conclusion based on unreliable data and inaccurate assumptions. According to a report published by PGEconomics, a consulting firm in the United Kingdom, in October 2009, herbicide-tolerant soybeans (3878, 15.00, 0.39%) and corn and cotton (17105, 150.00, 0.88%) were separately reduced in herbicides during 1996-2007. Use 4.6%, 6.0%, and 15.1%.
Actually, the main benefit of planting herbicide-resistant GM crops is not to reduce the amount of herbicides used, but to use low-toxic broad-spectrum herbicide glyphosate, which is not considered harmful to human health. However, "natural" crops often use several more targeted and more toxic herbicides. If herbicides are not used, weeding and weeding will not only take time and effort, but will also consume fuel, causing soil erosion and destroying the environment.
One objection to genetically modified crops is that the use of genetically engineered insect pests can only have a temporary effect and will be counterproductive in the long term because, under the influence of natural selection, pests will gradually develop resistance to toxic proteins, resulting in the emergence of so-called “super Pests." This is indeed a problem worthy of serious consideration. The U.S. Environmental Protection Agency has stipulated that a special planted ordinary crop must be kept around the field where insect-resistant GM crops are planted, so that pests have a refuge. In this way, those mutations that are resistant to toxic proteins will be diluted and super pests will not evolve. About 90% of insecticide-resistant corn and cotton growers have complied with this requirement. The pest-resistant crops have been widely promoted for more than ten years and no super pests have yet been discovered. But can this situation be maintained for a long time? Some experts believe that there should be greater and more “refugesâ€, but farmers are generally reluctant to increase losses in this area and it is even more difficult for them to implement it in developing countries. The key is how to pass the popular science education so that farmers understand the importance of this issue.
"Super pest" is a very inaccurate metaphorical statement. It just means that it can resist a specific toxin. It does not mean that it is a super monster that can resist all toxins and pesticides, and has particularly strong vitality and great harm. Therefore, even if there is a "super pest," that would mean that the kind of GM crop that was originally used to resist it would not be catastrophic. It is not a major disaster. We can transfer another toxin gene to destroy it.
There is a saying that planting genetically modified crops cannot be preserved, which is the plot of seed companies to exploit farmers. In fact, the transfer of crops to insect resistance, herbicide resistance, disease resistance and other genes will not affect the crop's reproductive ability. Of course, some special genes can also be transferred to make crop seeds lose reproductive ability. This so-called "Terminator technology" has been developed but there is no activity application. So why are the seeds of genetically modified crops often untainted? This is because they use hybridized species, and no seeding is caused by hybridization, and has nothing to do with the transgene. The non-transgenic hybrid rice and hybrid corn could not be planted. Farmers did not think this was a terrible thing.
In short, the genetically modified foods that are currently on the market have been theoretically verified and experimentally verified. They are all safe and do not stand up to the scrutiny and the evidence can be used to suspect their safety. This is true even in the long run. People's fear of genetically modified foods is mainly due to the lack of understanding of transgenic technology. Another reason is not understanding scientific methods. For example, if someone asks to prove that GM foods have no hidden dangers before they can be listed, it is impossible. No one can prove that any food has absolutely no hidden dangers. As with all technologies, of course, the poor use of GM technology may also be problematic. It may also be an accident, but we cannot deny it because it is harmful because of such concerns.
In fact, it is almost impossible to completely avoid genetically modified foods today. Most of the soybean oil in the domestic market (7600, 34.00, 0.45%), blended oil, almost all papayas, and a significant portion of tomatoes are genetically modified. Even if you avoid buying genetically modified products in the market, it is difficult to avoid eating in restaurants. Genetically modified foods have long since entered our lives, and they will only grow more and more. There is no need to panic, but we should learn to accept them.