What Is a GMO?

If you've followed the debate about GMOs with any sort of regularity, there's a strong chance you've come across a picture of a tomato stabbed by a giant syringe. That image, though a complete fiction, seems to perfectly capture what's preventing public acceptance of these foods: We don't really know what makes something a GMO.

GMOs aren't made with syringes and, at the moment, they aren't even made with tomatoes, at least not commercially. But that false image is everywhere, and surveys indicate consumers fear GMOs without knowing much about them.

So what exactly is a GMO?

FROM THE FIRST SWEET POTATO TO THE QUEEN'S CORGI

The initialism stands for "genetically modified organism," but it's a term lacking scientific precision. Moreover, it's hard to find an organism in any way connected to humans that hasn't been genetically modified, says Alison Van Eenennaam, a geneticist at UC-Davis who specializes in animal biotechnology. "I might argue that a great Dane or a Corgi are 'genetically modified' relative to their ancestor, the wolf," she tells Mental Floss. "'GMO' is not a very useful term. Modified for what and why is really the more important question.”

GMOs are often described as if they were a recent invention of our industrial food system, but genetic modification of food isn't new at all. It's been happening for many millennia: As long as farmers have been saving high-performing seeds for future harvests, we've had GMOs. Perhaps the earliest known example of a GMO is the sweet potato, which scientists believe became modified when wild sweet potatoes became infected, quite naturally, by a particular kind of soil bacteria. Realizing these sweet potatoes were edible, people began saving the seeds and cultivating them for future harvests. That was about 8000 years ago.

These days, when people say "GMO," they tend to mean one particular modification method that scientists refer to as transgenesis. As Van Eenennaam explains, transgenesis is "a plant-breeding method whereby useful genetic variation is moved from one species to another using the methods of modern molecular biology, also known as genetic engineering."

Transgenic crops and animals have been modified with the addition of one or more genes from another living organism, using either a "gene gun," Agrobacteria—a genus of naturally occurring bacteria that insert DNA into plants—or electricity, in a process called electroporation.

The first commercial transgenic crops debuted in the early 1990s: a virus-resistant tobacco in China [PDF] and the Flavr-Savr tomato in the U.S., which was genetically altered to not get "squishy." (It's no longer on the market.)

As to the health risks of GMO foods, the scientific consensus is clear: Transgenic crops are no riskier than other crops. Van Eenennaam points to a 20-year history of safe use that includes "thousands of studies, eleven National Academies reports, and indeed [the consensus of] every major scientific society in the world."

THE ROLE OF HERBICIDES AND PESTICIDES

Today, the most ubiquitous transgenic crops in the U.S. food system are cotton, soybeans, and corn, including those modified to resist the effects of the herbicide Roundup. Branded "Roundup Ready," these crops have been modified so that farmers can apply the herbicide directly to crops to control weeds without killing the crops themselves.

For farmers, the result was better weed control and higher yields. For critics of GMOs, these crops became their smoking gun. These opponents argue they're bad for the planet and bad for our health.

There's no question that use of glyphosate, the active ingredient in the herbicide Roundup, has increased since the introduction of GMOs, but measuring its environmental impact is a far more complex equation. For example, as glyphosate use has increased, so has the prevalence of conservation tillage, a beneficial agricultural approach that helps sequester carbon in the soil and mitigate the impacts of climate change.

Bt crops—transgenic crops modified with genes from the all-natural bacterial toxin Bt, short for Bacillus thuringiensis—have also reduced the use of insecticide, according to a 2016 National Academies of Science report.

And though evidence suggests herbicide use has increased since Roundup Ready GMOs were first commercialized in the U.S., herbicide use has increased amongst some non-GMO crops, too. Glyphosate also replaced more toxic herbicides on the market and, if farmers were to stop using it, many would likely replace glyphosate with another herbicide, possibly one that's more toxic. Glyphosate-resistant weeds are a problem, but banning glyphosate, or glyphosate-resistant GMOs for that matter, wouldn't solve the problem.

In recent years, opponents of GMOs have increasingly aimed their fire at glyphosate. The source of many of these claims is a 2015 assessment [PDF] by the International Agency for Research on Cancer (IARC) to categorize glyphosate as "probably carcinogenic." That categorization has been hotly contested by many scientists, as other governmental agencies have concluded glyphosate does not pose a carcinogenic hazard. And, in June, reporting revealed that the lead researcher at IARC withheld important studies from the research group's consideration.

Weighing criticisms of glyphosate against its benefits certainly brings up complex issues in our agricultural system, but ultimately these issues are not unique to GMOs nor would they magically disappear if transgenic technology were eliminated altogether.

OTHER METHODS OF GENETIC MODIFICATION

Most consumers probably can't name all the different methods of genetic modification, but there's a good chance they've eaten foods modified by one of these methods all the same. Layla Katiraee, a human molecular geneticist at Integrated DNA Technologies and a science communicator, has written about these methods to illustrate why it makes little sense to single out transgenic crops. Examples include polyploidy, which gave us the seedless watermelon, and mutagenesis, which scientists used to engineer a brightly colored grapefruit. As Katiraee points out, sometimes two different methods can even create a very similar end result. For example, the non-browning Opal apple was developed using traditional cross-breeding, while the non-browning Arctic apple uses transgenic methods to silence the genes that control browning.

Katiraee says the most common objections to GMOs aren't exclusive to transgenic crops: “Don't like ‘Big Ag'? They use all methods of crop modification. Don't like herbicide-tolerant crops? They've been made with other methods. Don't like patents? Crops modified by all methods are patented. If you go through the list, you won't find one [objection] that applies exclusively to transgenesis.”

Katiraee's arguments illustrate why it doesn't make sense to label transgenic crops "GMO" while omitting the non-browning opal apple or a seedless watermelon. And the non-GMO label can often be misleading. Van Eenennaam points to one of the more ridiculous examples: non-GMO salt. "Salt doesn't contain DNA, so salt cannot be genetically engineered," she says. "All salt is 'non-GMO' salt."

DISEASE-RESISTANCE SUCCESSES

The noisy GMO debate has often overshadowed the successes of lesser known, disease-resistant GMOs. Van Eenennaam argues that no one should object to these crops since protecting “plants and animals from disease aligns with most everyone's common interest in decreasing the use of chemicals in agricultural production systems, and minimizing the environmental footprint of food production." Examples include ringspot virus–resistant papaya in Hawaii [PDF] and the American chestnut, both rescued from the devastating effects of lethal plant viruses.

Disease-resistant crops often face an uphill battle for approval. In Uganda, scientists developed a disease-resistant banana that then faced difficult regulatory obstacles until a new law was finally approved in October by the country's Parliament. In Florida, where the disease called citrus greening has caused widespread crop damage and loss to the citrus industry, orange trees have been modified with a spinach gene to help crops resist the virus. But orange juice manufacturers will have to persuade consumers to buy it. 

Scientists have used transgenic modification to address health concerns too. For example, some variations of the wilt-resistant banana also include a boost of vitamin A. Scientists are working on a form of wheat that would be safe for people with celiac disease.

Van Eenennaam fears the controversy over GMOs has meant that, over the years, the public has missed out on important technologies. In the field of animal biotechnology, for example, animals have been produced that are resistant to disease, "that produce less pollution in their manure, [and] that have … elevated levels of omega-3 fatty acids," but none of these have been commercialized in the U.S.

Given that these crops and animals have a 20-year history of safe use, Van Eenennaam argues there's no reason that "fungus-resistant strawberries, disease-resistant bananas, and virus-resistant animals [should] sit on the shelf" unused.

Editor's note: This post has been updated.