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?


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."


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.


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 Katiraeea 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."


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. 

Essential Science
What Is Antibiotic Resistance?

The news is full of terms like "superbug," "post-antibiotic era," and an alphabet soup of abbreviations including NDM-1, MCR-1 (both antibiotic resistance genes), MRSA (a type of antibiotic-resistant bacteria), and others. These all refer to various aspects of antibiotic resistance—the ability of bacteria to out-maneuver the drugs which are supposed to kill them and stop an infection.

Now, there is concern that we could move back into a situation like that which existed in the early 20th century—a post-antibiotic era. Mental Floss spoke to Meghan Davis, a veterinarian and assistant professor of epidemiology at Johns Hopkins University, about some of the potential outcomes of losing antibiotics. "We have generations of recorded history that identify the risks to human society from infectious diseases that we are unable to treat or prevent," Davis warns.


If an individual becomes ill due to a bacterial infection, they typically see their physician for treatment. But in the years before antibiotics were discovered, people frequently died from scenarios we find difficult to fathom, including mere cuts or scratches that led to untreatable infections. Ear infections or urinary tract infections could lead to sepsis (bacteria in the blood). Arms or legs were surgically removed before an infected wound could lead to death.

When antibiotics were discovered, it's no surprise they were referred to as a "magic bullet" (or Zauberkugel in German, as conceived by medical pioneer Paul Ehrlich [PDF]). The drugs could wipe out an infection but not harm the host. They allowed people to recover from even the most serious of infections, and heralded a new era in medicine where people no longer feared bacteria.

Davis says the existence of antibiotics themselves has changed how we use medicine. Many medical procedures now rely on antibiotics to treat infections that may result from the intervention. "What is different about a post-antibiotic modern world is that we have established new patterns of behavior and medical norms that rely on the success of antimicrobial treatments," she says. "Imagine transplant or other major surgeries without the ability to control opportunistic infections with antibiotics. Loss of antibiotics would challenge many of our medical innovations."


One reason antibiotic resistance is difficult to control is that our antibiotics are derivatives of natural products. Our first antibiotic, penicillin, came from a common mold. Fungi, bacteria, parasites, and viruses all produce products to protect themselves as they battle each other in their microbial environments. We've taken advantage of the fruits of millions of years' worth of these invisible wars to harness antibiotics for our use. (This is also why we can find antibiotic resistance genes even in ancient bacteria that have never seen modern antibiotic drugs—because we've exploited the chemicals they use to protect themselves).

These microbes have evolved ways to evade their enemies—antibiotic resistance genes. Sometimes the products of these genes will render the antibiotic useless by chopping it into pieces or pumping it out of the bacterial cell. Importantly, these resistance genes can be swapped among different bacterial species like playing cards. Sometimes the genes will be useless because the bacteria aren't being exposed to a particular drug, but sometimes they'll be dealt an ace and survive while others die from antibiotic exposure.

And many of these resistance genes are already out there in the bacterial populations. Imagine just one in a million bacterial cells that are growing in a human gut have a resistance gene already in their DNA. When a person takes a dose of antibiotics, all the susceptible bacteria will die off—but that one-in-a-million bacterium that can withstand the antibiotic suddenly has a lot of room to replicate, and the population of bacteria carrying that resistance gene will dramatically increase.

If the person then transfers those resistant gut bacteria to others, resistance can spread as well. This is why it's important to keep control over antibiotic use in all populations—because someone else's use of the drugs can potentially make your own bacteria resistant to antibiotics. This is also why hand washing is important: You can unknowingly pick up new bacteria all the time from other people, animals, or surfaces. Washing your hands will send most of these passenger bacteria down the sink drain, instead of allowing them to live on your body.


Most importantly, never ask for antibiotics from your doctor; if you have a bacterial infection that can be treated by antibiotics, your doctor will prescribe them. Many illnesses are due to viruses (such as the common cold), but antibiotics only work against bacteria. It is useless to take antibiotics for a virus, and doing so will only breed resistance in the other bacteria living in your body, which can predispose you or others in your household and community to developing an antibiotic-resistant infection. Remember, those resistant bacteria can linger in your body—in your gut, on your skin, in your mouth and elsewhere, and can swap resistance genes from the mostly harmless bacteria you live with to the nasty pathogens you may encounter, further spreading resistance in the population.

Antibiotics are also used in animals, including livestock. Purchasing meat that is labeled "raised without antibiotics" will reduce your chance of acquiring antibiotic-resistant bacteria that are generated on the farm and can be spread via meat products.

Davis notes clients often requested antibiotics for their pets as well, even when it was an issue that did not require them. She explained to them why antibiotics were not necessary. She counsels, "Individuals can partner with their physician and veterinarian to promote good antimicrobial stewardship. Use of antibiotics carries risks, and these risks are related both to side effects and to promotion of resistance. Therefore, decisions to use antibiotics should be treated with caution and deliberation."

Essential Science
What Is Gluten?

Gluten is one of the most talked about topics in nutrition today—a quick googling yields more than 280 million results—and nearly everyone has an opinion on it. In 2014, talk show host Jimmy Kimmel summed up L.A.'s consensus on the subject: "It's comparable to Satanism." But despite the mother lode of information (and misinformation) available, few people actually know what it is. Mental Floss spoke to a pair of experts about this misunderstood substance. Here's the lowdown.

Gluten is a marriage of two proteins found in wheat, barley, rye, and oats. A marvel of food chemistry, gluten mixed with water transforms into a gluey, stretchy mass. Heat up the mixture, and you get a light, airy framework, making it a valued partner in the kitchen. "Gluten provides structure to baked products," Carla Christian, a registered dietitian and professional chef, tells Mental Floss. "Without gluten, you'll end up with a product that's crumbly and will fall apart because there's nothing holding it together."

Chefs and home cooks rely on gluten to provide the textural and aesthetic qualities in baked goods such as breads, pastries, and cakes. Gluten also plays an important nutritional role, providing a tasty source of plant-based protein in seitan and other meat substitutes, including mock duck, with its strange "plucked" texture.

Its culinary and nutritional qualities notwithstanding, gluten has a darker side. "For some reason, gluten seems to be the trigger in developing celiac disease in those who are genetically susceptible," Runa D. Watkins, an assistant professor and pediatric gastroenterologist at University of Maryland's School of Medicine, tells Mental Floss.

Celiac disease is an autoimmune disorder that affects the small intestine. When a person with celiac disease eats foods containing gluten, their immune system reacts by attacking their small intestine, destroying its ability to digest and absorb nutrients. Celiac disease can cause diarrhea, bloody stools, skin rashes, vitamin and mineral deficiencies, and a host of other unpleasant symptoms.

Although as much as 40 percent of the population carries the gene for celiac disease, fewer than 1 percent—roughly 3 million people in the U.S.—will develop the condition. Why some do, and others don't, is a mystery, says Watkins. The prevailing theory is that some sort of infection is the trigger. One recent study found a virus that can cause celiac disease.

The default setting in the human gut is one of tolerance. It typically receives all visitors (in the form of foods, beverages, or microbes) and allows them to pass without argument. After an infection, however, the gut can become hypervigilant—overly cautious about who comes and goes. In some cases, gluten becomes an unwelcome guest.

Although scientists aren't sure why gluten becomes so offensive, the reasons may lie in the protein's unique makeup.

Proteins are strands of amino acids folded into long, twisty coils. Gluten is rich in two particular amino acids, proline and glutamine, that set it apart from other proteins.

Proline makes gluten "kinky"—helping it form a tight, compact structure that's nearly impenetrable to digestive enzymes, a biological version of a lock-on. Some scientists believe gluten's impervious nature is responsible for triggering an overzealous immune response in susceptible people.

The glutamine in gluten (say that five times, fast) is a target for an enzyme called tissue transglutaminase, or tTG for short. Under certain conditions, tTG goes rogue: It alters glutamine's otherwise benign structure, making it more allergenic and initiating a cascade of immune-related events that ultimately leads to the development of celiac disease. When doctors test for celiac disease, they look for abnormally high amounts of antibodies like tTG in the blood. However, the only definitive way to diagnose the condition is by biopsy of the lining of the small intestine.

The only "cure" for celiac disease is total avoidance of gluten. "If a person has celiac disease, even a little bit of gluten can make them very sick," says Christian.

That can be hard, because gluten is everywhere. It can be found in the usual wheat-containing suspects (breads, pasta, cereals), less obvious candidates (communion wafers), and hidden in strangely odd places (soy sauce, beer, and some cosmetics). The average person consumes between 4 and 20 grams of gluten per day. Most of that comes from wheat-containing bread: One slice contains about 4 grams of gluten. To counter this abundance—and to capitalize on the myth that gluten is bad for everyone—a thriving gluten-free market has emerged. In 2015, one market analysis estimated that the global market for gluten-free foods was worth roughly $4.2 billion; an analysis from May 2017 put it much higher, at nearly $15 billion

With celiac disease affecting only 1 percent of the population, why are so many people buying and eating gluten-free foods? Gluten takes the blame for a litany of other ills, ranging from skin disorders and headache to fibromyalgia and psychiatric problems, often lumped into a condition known as non-celiac gluten sensitivity, or NCGS, for short. The number of people with NCGS may be high—as many as 18 million people in the U.S.—but its occurrence is hard to measure.

"Unfortunately, there's no specific test for [NCGS], so it's basically a diagnosis of trial and error after ruling out celiac disease," says Watkins. Scientists aren't in agreement that NCGS is a legitimate health concern, however, and some suggest its symptoms might be due to something unrelated to gluten.

With all the talk about gluten, it seems gluten sensitivities are becoming more common. "Celiac disease is becoming more prevalent because we're doing a better job of finding it, I think," says Watkins. But the rest of it? Probably just a fad.

Editor's note: This post has been updated.