Since scientists first began to test genetically engineered crops in the late 1980s, the idea of tinkering with the DNA in our food supply has been one of the most controversial subjects that you could imagine. To some, GMOs (genetically modified organisms, which include both plants and animals) are a breakthrough scientific advance, one that will provide us with bigger crop yields and more nutritious food, and help farms in developing nations produce enough to banish hunger. To others, GMOs are "Frankenfood," a nightmarish example of science run amok, which poses grave potential risks to both human health and the environment.
The sharp division over GMOs isn't just ideological, but international as well. In the U.S., the Food and Drug Administration (FDA) decided in 1992 that GMOs weren't inherently dangerous and didn't require special regulation [source: American Radio Works]. Today, about 60 to 70 percent of U.S. processed foods have ingredients derived from GMOs [source: Dupont]. By contrast, in Europe, the European Union imposed far more stringent regulations. Only about 1 percent of farmland has GMO crops under cultivation, and very few processed foods contain them [source: Barber].
GMO proponents point to approval from independent scientific organizations such as the National Research Council, which concluded in 2010 that GMOs actually have fewer adverse effects upon the environment than ordinary crops grown with pesticides, and the World Health Organization, whose Web site states that studies on genetically engineered foods show they "are not likely to present risks for human health" [sources: NAP, WHO]. Critics charge that safety research on GMOs is insufficient because it tends to focus on short-term rather than long-term effects, which they warn are unknown [source: Barber].
As often is the case with scientific controversies, the truth is far too complex and needs too many qualifications to fit on a bumper sticker. Here's a look at 10 assertions about GMOs that are frequently uttered by debaters, and the actual truth behind them.
Genetic Modification of Food Is New
Not really. Critics of GMOs often portray genetic tinkering as an unnatural break from farming's pastoral heritage. But in truth, we've messing with the DNA in our food since the dawn of agriculture, by selectively breeding plants and animals with desirable traits [source: Scientific American].
Those plump-kerneled, golden-yellow ears of corn that we love to slather in butter didn't exist 10,000 years ago. Instead, ancient humans took a wild, scraggly grass called teosinte, which has comparatively tiny cobs and kernels, and crossbred the most robust specimens. Modern geneticists who've analyzed the DNA from modern corn and its ancient ancestors found that it took just a small alteration in the genome — about five regions of either single or groups of genes — to change teosinte into the earliest varieties of maize (another word for corn). But minor changes to influential genes can make a huge difference. In genetics, this sort of human intervention in evolution is called artificial selection [source: University of Utah]. Artificial selection over the centuries has increased crop yields and created foods that are bigger, more resistant to pests and disease, and tastier [source: American Museum of Natural History].
GMOs Are Just a Modern Version of Selective Breeding
Well, yes and no. It's true that traditional breeding, purposely growing plants or crossbreeding them for certain characteristics, can be a messy business. Since plants often exchange large, unregulated chunks of their genomes, breeders may end up getting unwanted traits along with the ones they're seeking. For example, potato varieties created through conventional breeding sometimes produce excessive levels of chemicals called glycoalkoloids, which can be poisonous. And it may take many generations to get the characteristics that breeders are trying to achieve [source: University of California San Diego].
Genetic engineering is a bit more systematic. Basically, scientists extract DNA from one organism, copy the gene that's responsible for desired characteristics — called a transgene — and then put it into another organism. They do this either by inserting it into a bacteria and infecting the organism with it, or by using a gene gun, which shoots microscopic gold particles covered with copies of the transgene into the organism. Since they can't control whether the transgene inserts into the recipient's genome, it can take hundreds of attempts to get a few GMOs [source: University of Nebraska -Lincoln].
But there is one really significant difference. Genetic engineering can produce much more radical changes in plants and animals than selective breeding ever could. Scientists, for example, have implanted monkey embryos with a jellyfish gene to breed monkeys with glowing green feet [source: Coghlan]. It's not hard to imagine how the power to create a plant or animal with freaky characteristics could be misused, either accidentally or on purpose.
There's Solid Evidence That GMO Foods Cause Cancer
Not exactly. A 2012 French study found that rats fed a lifetime diet of genetically modified corn that made it resistant to the herbicide Roundup— or else given water containing Roundup — suffered tumors and organ damage. The researchers reported that 50 percent of male rats and 70 percent of females died prematurely, compared with only 30 percent of males and 20 percent of females in a control group [source: Reuters].
That made for a scary-sounding headline. But as routinely happens in the world of science, other researchers who had come to different conclusions in their own work started scrutinizing the study. Six French scientific academies quickly issued a rebuttal in which they found fault with the design of the experiment, the statistical analysis and the amount of data. The European Food Safety Authority declared that the study was "of insufficient scientific quality to be considered as valid for risk assessment." Additionally, the strain of rat that the researchers picked tends to get breast tumors easily, and can get them from overeating or eating corn contaminated by a common fungus that causes a hormone imbalance. The study didn't screen for those factors, so it's unclear whether the rats' tumors were caused by the GMO corn [source: MacKenzie].
GMO Crops Are Dangerous Since They Contain Toxic Substances
Some GMOs — for example, a variety called Bt corn — actually do contain a pest-killing toxin. That may sound pretty dangerous, until you stop to consider that unlike, say, chemical insecticides and herbicides, the toxin in the Bt corn is engineered to work on specific ravenous insects, and doesn't affect other species, including humans.
A recent Scientific American article that summarized the research on Bt corn noted, "The evidence overwhelmingly demonstrates that Bt toxins are some of the safest and most selective insecticides ever used. Claims that Bt crops poison people are simply not true." Indeed, the article argues that when properly managed, fields of Bt corn actually help protect the environment, because they reduce the use of broad-spectrum insecticides that kill off insects, including beneficial ones, indiscriminately [source: Jabr].
Even so, there are downsides. One problem is that pests can become resistant to genetically engineered toxins, just as they can develop immunity to pesticides. For example, farmers in the Midwest have discovered that one variety of Bt corn no longer repels the root-chomping beetle larvae that it's meant to stop. If GMOs fail to be pest resistant, that might lead farmers to start dousing their fields with problematic chemicals again [source: Jabr].
GMO Crops Pose a Health Risk to People With Allergies
This was one of the first big fears that people had about GMOs. If you know that you're deathly allergic to peanuts, you'll probably stay away from peanut butter. But if a scientist puts peanut genes into some other food, would you have to avoid it as well, and how would you know they were even there?
There actually is an example of this happening. Back in the mid-1990s, scientists found that a Brazil nut protein, added to improve the nutritional quality of genetically engineered soybeans, had the ability to cause an allergic reaction in people sensitive to Brazil nuts [source: Nordlee et al.].
Unwary consumers never actually got sick from eating those soybeans. That's because the researchers discovered the dangerous effect during the development process and ultimately abandoned that particular GMO [source: Palmer].The allergy risk could be nipped in the bud by such safety testing, which is why the American Medical Association, among others, has called for mandatory pre-market safety testing of GMOs [source: Eng].
The FDA doesn't require allergy screening, but instead uses a "voluntary consultation process" to look at safety. And while the agency hasn't found any GMOs that cause allergy problems so far, it's possible that some might slip through the regulatory cracks. The answer might be for Congress to mandate such testing and provide funds for it, but don't hold your breath waiting for that to happen.
Altered Genes From GMO Plants Invariably Will Spread and Cause Havoc
It's possible to conjure up all sorts of terrifying scenarios. What if a GMO gene that causes resistance to antibiotics somehow is transferred from a food into pathogenic bacteria in your gastrointestinal tract? That could make you really, really sick [sources: WHO, Palmer]. But it's probably not going to happen. Dutch scientists, who looked at the risks of specific bacteria being altered by GMO genes in a 2005 study, found that the data "does not give rise to health concerns" [source: Kleter et al.]. And an Australian government scientist concluded in a 2008 study that the frequency of such gene transfers from plant-based foods to microorganisms is so low that it "poses negligible risks to human health or the environment [source: Keese]. Nevertheless, the World Health Organization (WHO) doesn't want to take any chances, and is urging member countries to pick GMOs that don't have antibiotic resistance.
Another potential problem is outcrossing, in which genes from GM plants spread into conventional crops or wild species. Traces of a type of corn only approved for animal use, for example, once began to show up in corn products for human consumption. Some countries have adopted regulations to reduce mixing, including a clear separation between fields with GM and conventional crops [source: WHO]. And a 2006 Australian government report noted that outcrossing could be controlled by making GMO plants' pollen sterile [source: Mills].
If Patented GMO Seeds Accidentally Grow on Your Property, You Could Be Sued
Like many of the fears about GMOs, this is one that has a germ of truth in it. In 1999, agribusiness giant Monsanto sued a Canadian organic canola farmer, Percy Schmeiser, for growing the company's pesticide-tolerant canola without paying the required fees. The farmer, in his defense, argued that he hadn't planted any of the company's GMO canola seeds, and that they must have blown onto his property.
An NPR journalist who investigated the issue of windblown seeds in 2012, reported that he didn't find any cases where Monsanto had sued anyone over trace amounts of seeds introduced through cross-pollination [source: Charles].
GMO Crops Cause Catastrophic Honeybee Decline
This seems to be a case of guilt by association. Between 2008 and 2013, 30 percent of bees in the U.S. have either disappeared or failed to pollinate blossoms in the spring. It's even worse in some other countries — Spain has lost close to 80 percent of its beehives [source: Entine]. Some beekeepers and environmental activists have argued that the cause is a powerful class of pesticides called neonicontinoids, which are similar in structure and action to nicotine. Unlike the usual pesticide sprays, neonicontinoids are absorbed by plants and relocated through their vascular systems, so that boring insects will suck them up [sources: Wines, Oliver].
These pesticides are different from GMOs, though activists sometimes lump them together, possibly because the pesticides are sometimes used to treat seeds. There's no solid evidence that GMOs themselves are causing the bee collapse. That said, GMOs may not necessarily be so great for other insects. There are recent studies that indicate that in rare instances, they may inadvertently kill butterflies, ladybugs and other harmless or even beneficial insects [source: Jabr].
Almost All Crops Today Are GMOs
It is true that since GMOs were introduced in the 1980s, people in the U.S. have consumed a lot more of them. By one estimate, 70 percent of processed foods in the U.S. contain genetically modified ingredients [source: Scientific American].
But that's largely because a few big-ticket crops — corn, in particular— are used in a lot of foods. According to one anti-GMO Web site, there are around 60 GMOs that have been approved in the U.S. for human consumption or animal feed. That list includes 20 varieties of corn, 11 varieties of oilseed rape/canola, 11 varieties of cotton, six tomato varieties, three types of soybeans and sugar beets, two different squash varieties, and single types of cantaloupe, rice, flax, radicchio, papaya, alfalfa and wheat [source: Organic Consumers].
But of all those crops, only corn, soybeans, cotton, canola, squash, and papaya grown in Hawaii currently are being commercially cultivated. Some were tried but eventually taken off the market, while others — like wheat and rice—have never been grown in the U.S. [source: Organic Consumers]. The upshot is that most of the vegetables and fruits in your local supermarket are non-GMOs.
One big reason GMOs haven't caught on even more extensively is that U.S. consumers are suspicious of them. According to a June 2013 ABC News poll, 52 percent of Americans believe such foods are unsafe [source: Langer].
GMOs Are Unlabeled and Impossible to Avoid
It is true that the federal government doesn't require food from animals that have been raised on feed from GMO plants to be labeled. However, in June 2013, the U.S. Department of Agriculture officially approved a label that food companies can use to identify meat and liquid egg products that come from animals that haven't been fed GMOs. All these producers have to do is provide proof that they've been vetted by an independent certifying organization [source: Strom].
Additionally, some specialty grocery store chains are trying to keep their distance from GMOs. Trader Joe's, for example, recommends that consumers concerned about genetic engineering buy its organic-labeled meats and dairy products and wild-caught seafood. Another chain, Whole Foods, announced that by 2018 all products in its U.S. and Canadian stores will be labeled to indicate whether or not they contain GMO ingredients, and it will label some animal products as non-GMO verified.
But unless you grow your own food, perhaps the surest way to avoid GMOs is to live in Europe. Since the late 1990s, the European Union has required labeling of food products containing GMOs, and as a result, European food retailers — fearful that the labels would drive away customers — have kept them out of their wares. As a recent Scientific American editorial notes, "It is virtually impossible to find GMOs in European supermarkets."
HowStuffWorks talks to the scientist behind the oft-repeated (and misleading) statistic that humans and bananas share 50 percent of the same DNA.
Author's Note: 10 Misconceptions About GMOs
I wasn't particularly well-versed in the controversy about GMOs before I researched this article, though like many people, I probably harbored a vague unease about so-called "Frankenfoods." After learning more about the subject, however, I've developed a more nuanced view. It's not easy to dismiss all the concerns that people opposed to GMOs have, and it makes sense to me that consumers should be able to decide if they want to consume GMO foods or avoid them. But I also think there's a powerful argument to be made that GMOs actually can be good for people, particularly in developing countries where malnutrition remains a serious problem. For example, one GMO, Golden Rice, which has been designed to produce the vitamin A precursor beta-carotene, could play a big part in fighting vitamin A deficiency, which kills 250,000 children worldwide each year and blinds another 500,000.
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