The subject of genetically modified organisms (GMOs) is one of the most hotly debated food and environmental topics in the world today. Just look at the response to Chipotle’s recent announcement that the chain would cease to include GMO ingredients on its menu. Health advocates applauded the move as a step in the right direction on the heels of Whole Foods’ 2013 commitment to label all genetically modified products in its stores by 2018. Detractors called it yet another example of a food maker using unsubstantiated claims to sell food and hypocritical, given that the chain will continue to serve soda, which contains high-fructose corn syrup made with genetically modified corn.

At the crux of the controversy are a number of unknowns about the long-term health effects of ingesting genetically modified (GM) foods and the impact these plants and accompanying farming methods have on the environment. With some experts saying 60 to 70 percent of food products contain GMOs in recent years, it’s clear this issue is central to the future of our food supply. To help answer some commonly asked questions and further a constructive dialogue on the topic, here is a brief overview of the facts we know today.

What Are GMOs?
A genetically modified organism is a plant or animal whose DNA has been modified without using natural methods of reproduction. Individual genes are transferred from the “source” organism into the DNA of the “target” organism. This produces crops that carry certain traits such as resistance to insect damage or improved nutritional value.

As an example, in the case of the genetically modified Bt corn, genes from a soil bacterium called Bt, which carry a trait making it resistant to insect destruction is inserted into the plant. As a result, such a corn crop would be safe from the adverse effects caused by insects that might otherwise cause loss or damage.

There are currently no genetically modified animals approved for sale and consumption in the United States, although the feed of conventionally raised livestock and poultry often contains genetically modified ingredients.

Are GMOs Safe?
Many proponents of genetically modified foods state that they are completely safe to eat and that this process has taken place in nature for thousands of years. They cite research such as a review by Snell et al., which carried out a comprehensive analysis of 24 studies on the health effects of animal diets containing genetically modified feed. The authors determined that, “the studies reviewed present evidence to show that GM plants are nutritionally equivalent to their non-GM counterparts and can be safely used in food and feed.” Any differences observed between conventional and GM feed “fell within the normal variation range of the considered parameter and thus had no biological or toxicological significance.”

However, not everyone is convinced. A joint statement developed and signed by over 300 independent researchers asserts that contrary to popular claims, there is “no consensus on GMO safety,” and that differences of opinion are present regarding the interpretation of the safety parameters employed by the review’s authors. Furthermore, the design of the studies profiled by Snell et al. were called into question.

These same scientists are concerned that despite the common claim that “trillions of GMO meals” have been consumed in the United States without any adverse effects, no epidemiological studies (observational studies used by researchers to test the relationship between factors and determine the existence of correlations) in human populations have been carried out to support this declaration. The authors go on to state that “as GM foods and other products are not monitored or labeled after release in North America, a major producer and consumer of GM crops, it is scientifically impossible to trace, let alone study, patterns of consumption and their impacts. Therefore, claims that GM foods are safe for human health based on the experience of North American populations have no scientific basis.”

There is also growing concern regarding the chemicals that certain GMO foods are treated with, particularly in the case of “Roundup Ready” crops. Roundup is the brand name for the herbicide glyphosate, produced by Monsanto, an American agrochemical and agricultural biotechnology corporation responsible for most of the transgenic varieties of crops in the world today. Many GMOs such as soy, corn, canola, alfalfa, cotton, and sorghum are designed to be resistant to the effects of Roundup. These patented breeds of plants make it possible for farmers to spray crops with the herbicide to kill weeds without threatening their harvest. Unfortunately, an agency of the World Health Organization has cautioned that glyphosate “probably” causes cancer, which naturally raises alarm bells about the safety of these foods.

Of course, this is not to say that genetically modified foods are categorically unsafe. However, it is apparent that research on this topic is young, emerging, and far from being conclusive.

What About the Environment?
It is equally important to understand the effects of GM crops on our environment. Proponents of this technology will argue that GMOs increase yields while decreasing the use of chemical pesticides (a seemingly win-win situation). However, it has been shown that this is not necessarily the case. A study examining the history and sustainability of U.S. staple crop production, such as soybean, maize, rapeseed, and cotton, in the American Midwest showed that, “relative to other food secure and exporting countries (e.g. Western Europe) [which unlike the U.S., are highly conservative when it comes to GMOs], the U.S. agroecosystem is not exceptional in yields or conservative on environmental impact.” Another study has determined that herbicide and insect-resistant crops has led to a 527 million pound increase in herbicide use in the United States between the years 1996 and 2001, while only decreasing insecticide use by 123 million pounds. In other words, while the use of insecticides has decreased, the use of herbicides has increased much more substantially, likely due to the proliferation of glyphosate-resistant weeds.

The development of such “super weeds” is another growing concern. Indianapolis-based Dow AgroSciences, a division of Dow Chemical that specializes in biotechnology and agricultural chemicals, has recently gained approval bring its Enlist weed control system to market. Enlist weed control is the company’s answer to weeds that have developed a resistance to Monsanto’s Roundup herbicide (they infest over 70 million acres of farmland in the US!), and is designed to be used in tangent with GM corn and soybeans. Enlist contains the chemical 2,4-D (a highly controversial chemical) in addition to glyphosate. The prevalence of these herbicide-resistant weeds and the industry built around solving this problem raises many questions: What happens when weeds eventually become resistant to Enlist? Is it sustainable for us to continue to rely on increasingly potent (and controversial) herbicides in support of this technology? Are we imprisoning the farmers who adopt these modern methods into a perpetual technology trap?

Other highly important environmental issues include the potential for GMOs to cross-pollinate with other crops and plants in the ecosystem, the challenge of maintaining biodiversity in the era of industrial crop production, the role and potential benefits of agroecology, the effects of GMOs on farmers (particularly in the developing world), and of course, the ethics behind the commoditization of nature, a worldview which certainly shapes much of the agribusiness industry. All of these issues must also be addressed as we evaluate the risks and potential benefits of this technology.

There are no easy answers to the question of GMOs, and it appears that they will continue to be a part of our food landscape in the foreseeable future. However, much is at stake. Objective, independent research, and constructive discussions among all stakeholders (corporations, farmers, legislators, researchers, environmental groups, and the public) must take place if a responsible solution is to be reached. In the meantime, those who wish to exercise caution by avoiding GM foods can do so by buying organic when possible (by law organic foods cannot contain GMOs), and by supporting local farmers who do not employ this technology.