Like most mothers, Siree Franks, 34, of Los Angeles, worries about the diet of her two young children. Although her busy lifestyle could easily lend itself to quick food fixes, Franks works hard to make sure her children eat plenty of whole foods and limited sugary, processed snacks. And, though she’s not totally clear on the science behind it, she also avoids all genetically modified organisms, or GMOs.

“The further you get from nature—in my opinion, it isn’t good for you,” says Franks. “What I’m confused about is, when they modify something, is there anything that is being taken away? Or does it change the way we absorb it or digest it? Does more beautiful or fatter corn affect your body the same way as regular corn?

It seems like when you tamper with things, something happens.”

Franks voices the concerns many consumers have about GMOs. A dearth of safety information and time-tested research has left us unclear about how these new food products affect our health. In fact, there are a number of substantiated health-related problems with GMOs, including potential allergic reactions and an increase in antibiotic resistance. Serious environmental side effects of GMO crops include widespread overuse of pesticides and herbicides, as well as accidental, often pollen-borne “contamination” of neighboring non-GMO and organic crops. Finally, many Americans worry that the Food and Drug Administration’s (FDA) regulation process inadequately safeguards U.S. consumers and allows the multinational corporations that manufacture GMOs to unfairly control our food supply—and, ultimately, its safety.

What is a GMO, anyway?
A GMO is any organism that has been artificially altered at the genetic level to gain—or lose—certain important characteristics. “Genes are recipes for proteins,” explains Alan McHughen, PhD, a plant biotechnologist at the University of California, Riverside. “The presence or absence of a particular protein is what gives all living things their various genetic traits. Genetic engineering allows us to move precise genes from one living thing to another in order to transfer specific, usually desirable, features.”

On a commercial level, these desirable features include a crop’s ability to resist pests and weeds or to withstand the ravages of chemicals used to kill them. Many farmers like this technology because it allows them more control over the success of their crops, minimizing or even eliminating major crop hazards. Thanks to high demand, large agribusiness corporations that manufacture GMO seed stand to make large sums of money.

Although GMOs have been around for more than 30 years, only recently did they begin to dominate certain agricultural sectors. In 1973, American scientists Stanley Cohen and Herbert Boyer first removed a select piece of DNA from one species of bacteria and inserted it into another. It wasn’t until 1986 that the Environmental Protection Agency (EPA) approved the release of the first genetically engineered crop: tobacco. Since then, scores of genetically altered food items have been introduced to the market, including tomatoes, papayas, corn, and soy.

Between 1995 and 2004, according to the U.S. Department of Agriculture, the percentage of GMO soy and corn planted in the United States has ballooned from 7 percent to 85 percent, and from 1.5 percent to 45 percent, respectively. Last year, GMO wheat was headed for approval and planting in the United States, but Monsanto, its manufacturer, held off releasing it because of negative public perception. Unlike soy and corn, which are often used for animal feed and other purposes, the majority of wheat is intended for human consumption.

How GMOs affect health
With GMOs comprising a growing sector of the market comes an increasing number of questions about their impact on human health. The unspoken (and thus far unfounded) fear is that eating “mutant” food over the long run could lead to major illness, such as cancer, or other unknown health problems. Instead, the health risks we do know about are much more mundane. The primary current concern with GMOs is that their altered proteins may cause allergic reactions in susceptible people. Symptoms might range from simple nausea to death by anaphylactic shock, if, say, a peanut gene was inserted into a GMO food.

FDA rules do state that no GMO food will be released under the same name if it is “significantly different from its traditional counterpart,” but there have been scares. In 1995, international seed company Pioneer Hi-Bred developed a modified soybean that included a select gene from a Brazil nut. Before releasing the soybean, the company had it tested for abnormalities at the University of Nebraska, where researchers discovered that the Brazil nut gene used was one that causes allergic reactions in some humans.

Pioneer Hi-Bred caught the problem, but the episode raised questions as to what could happen if a GMO plant intended for one purpose commingled with that of another. This scenario played itself out in 2000, when genetically modified corn intended for animal feed showed up in human food products across the United States. The corn, called StarLink, contained Cry9c, a protein that proved difficult for the human digestive system to break down, thus increasing the possibility of allergic reaction. All contaminated food products—including Kraft’s Taco Bell taco shells, Kellogg’s Morningstar Farms meatless corn dogs, and Mission Foods tortillas—were recalled, but not before 51 people filed “adverse event reports” with the FDA, saying they experienced dizziness, weakness, loss of consciousness, dermatological outbreaks, and vomiting.

The Centers for Disease Control eventually concluded that StarLink did not cause these reactions, but the event increased doubt not only about the safety of GMO foods but also about our ability to segregate and track GMO and non-GMO crops. This challenge is set to become even more daunting with a new generation of GMOs, which offer nutritional or pharmaceutical benefits in addition to agricultural benefits, on the horizon.

For example, plant-made pharmaceuticals (PMPs) are drugs or the agents used to make drugs—say, the components for insulin—developed relatively cheaply inside a GMO plant. Already, PMPs have caused problems. In 2002, remnants of a PMP researcher’s Nebraska research crop were found in a non-GMO soy crop grown later in the same field. As a result, the FDA ordered the disposal of 500,000 bushels of soy. No further regulation resulted from this discovery, which was touted as a victory because the problem was caught.

Another highly underreported health risk of GMOs stems from the way the seeds are manufactured. When manufacturers insert select genes into new GMO plants, they include an antibiotic resistance marker gene that makes it easier to test the new plants and ensure that the transgenic process worked. To test the new GMO seeds, they grow them in an antibiotic “broth.” Seeds that survive have accepted the new genetic material; those that die have failed.

The unintended result of this technique is that our environment is being flooded with genes that resist antibiotics. In a worst-case scenario, these genes would eventually link up with bacteria in animals and humans and make the bacteria immune to clinical antibiotics. Ultimately, we would be unable to cure the most commonplace bacterial infections.

“Of course, it is possible for antibiotic-resistant bacteria to transmit that resistance to other bacteria,” says Marion Nestle, PhD, MPH, professor and chair of the nutrition and food studies department at the Steinhardt School of Education at New York University. “There is now plenty of proof that penicillin no longer works on bacteria that used to be killed by it. You can go to a grocery store, buy ground meat, test its bacteria, and see that they are now resistant to all kinds of antibiotics. This is a problem, and a really scary one.”

GMOs’ global impact
While debate continues over evidence suggesting that GMOs pose health risks, there is less debate regarding GMOs’ environmental effects. A Cornell University study showed that pollen from a particular strain of GMO corn, Bt corn, was killing Monarch butterfly populations (Nature, 1999, vol. 399, no. 214).

And although many GMO seed manufacturers claim that using GMO seeds decreases the amount of pesticides and herbicides needed (because varieties like Bt corn are inherently impervious to blights), the opposite has proven true. Because the majority of GMO crops are designed to withstand herbicides’ effects, crops are being overtreated simply because they can be.

Two agricultural journals in particular, Successful Farming and Farm Journal, are engaging in running discussions about the overuse of glyphosate, the herbicide that certain varieties of GMO corn and soy have been designed to resist. Glyphosate overuse has become so prevalent that a severe rash of herbicide-resistant weeds, predominantly marestail, has developed and is choking crops, GMO and non-GMO alike. The outcome of this development is uncertain.

The EPA generally considers glyphosate safe for humans and the environment because it is nontoxic in small doses and has a short half-life (an average of 60 days). However, the danger of glyphosate overuse is serious because, just as with antibiotic resistance, we are raising the stakes against the environment. The more we push to change it, the more it changes in response, often unpredictably. There may come a time when none of our techniques for combatting weeds, insect pests, or bacteria work any longer. And this could mean irrevocable damage to our food supply and, ultimately, our health.

Perhaps due to GMOs’ environmental implications for the planet as a whole, many governments outside the United States have acted on their citizens’ behalf, either by limiting GMO planting or requiring special labeling for foods containing GMO product. The European Union, for example, requires labels on foods that contain more than 0.1 percent GMO seed content, though it is debating raising that threshold to 0.3 percent.

Currently, 90 percent of GMO crop production takes place in just three countries: the United States, Canada, and Argentina. GMOs have gained relatively rapid access to the U.S. market thanks to the FDA’s industry-friendly regulation process. The European Union tests new food items before allowing them to go to market; the United States allows foods to be released based on tests conducted by the manufacturer. If and when problems are reported, the FDA launches its own investigation.

The only currently viable way for U.S. consumers to avoid GMO foods is to look for products labeled as non-GMO or organic.

The FDA has drafted guidelines for voluntary labeling, but most food manufacturers have declined to follow them. The only currently viable way for U.S. consumers to avoid GMO foods is to look for products labeled as non-GMO or organic.

Unfortunately, even this method is superficial, because as pollen or seeds blow between nearby fields, non-GMO crops have increasingly become contaminated by GMO crops. They may also be accidentally commingled during transportation from the field to the market.

GMO corn that escapes into non-GMO fields is particularly vexing for organic farmers who have lost whole crops because of it.

“Non-GMO farmers worry about three things: retention of markets, the potential for accidental commingling of GMO with non-GMO product, and genetic drift,” says Kathleen Merrigan, PhD, director of the agriculture, food, and environment program at Tufts University Friedman School of Nutrition, Science, and Policy. “The problem of genetic drift, where, for example, GMO corn escapes into non-GMO fields, is particularly vexing for organic farmers who have lost whole crops because of it. Scientifically, we don’t know how to prevent it, and current regulations for buffer barriers—25 yards between fields—are likely to be insufficient.”

Is the GMO jury still out?
Before consumers rush to judgment on GMO foods, many experts say, they must look at the whole picture of all the dangers posed by our food supply.

“If you look at real risks to health, harmful bacteria and viruses in foods rank number one,” says Nestle. “They are responsible for millions of cases, hundreds of thousands of hospitalizations, and several thousand deaths each year. But they don’t scare people nearly as much as pesticides, irradiation, or genetic engineering. Even though nobody has ever died from eating a genetically modified food—as far as we know—it scares people. They can’t tell whether it’s safe, they didn’t ask for it, it was imposed on them, and they have no control over it. That’s why it was so important to label genetically modified foods, and it was such a mistake not to.”

In other words, dangers posed by listeria, salmonella, and E.coli are much greater than those posed by GMOs. But because we can’t completely control our exposure to GMOs, or their proliferation, we are less inclined to accept the risks. For Siree Franks, the decision to avoid GMO foods was both philosophical and practical: “I can imagine what’s being gained with GMOs, but I don’t know what’s being lost—if it’s something that could later be a problem, or something we needed. I’m not too happy about that.”

Whatever your position, GMO food crops won’t be going away anytime soon. Now may be the time to get involved and learn more (see “Does Your Food Have GMOs?”). Most experts share Merrigan’s view that existing GMO foods are safe. But, she says, “it’s those GMO foods on the horizon that give us pause and leave us wondering if current laws and regulations are sufficiently rigorous for the next generation of products.”