Do GMO Crops Harm Gut Bacteria?

When I was growing up I wanted to be a genetic engineer. While life eventually brought me in a different direction, my interest in genetic modification has not waned, but rather expanded. In 2001, while I was attending naturopathic medical school, the consideration of mandatory labeling for genetically modified (GMO) food was being taken up by FDA. As public commentary was invited, I offered them my opinion which was that GMO foods should be labeled for the simple reason that people have the right to know what is in their food, and how it is produced.

I wasn't convinced that there was an inherent problem with the concept of genetic engineering. I'm still not. This is because there are a whole host of ways that the process of genetic engineering can be used for clearly beneficial purposes. For example, we could genetically engineer microbes which digest our trash and toxic waste, turning it into material for our 3D printers. Or perhaps we could engineer vegetables to be more nutritious, or herbs to be more medicinal.

Back in 2001, hardly anybody, it seemed, knew much about GMO crops. Even fewer cared to know. Yet now GMOs have gone viral, and the issue of mandatory labeling of GMO foods has risen to the national stage. GMO food has become all but synonymous with Monsanto, the transnational food behemoth which pioneered genetic engineering techniques for two of the world's largest staple crops: corn and soy.

It didn't have to happen this way- and still doesn't. But is a blanket banning of genetic modification the solution? In order to better answer this question, it may help to set aside the fiery rhetoric for a moment, and take a closer look at some facts.

Prologue: The Story of Glyphosate

Glyphosate is a herbicidal chemical discovered by a Monsanto scientist in 1970. It was heralded as a major breakthrough in agricultural science precisely because it is toxic to plants, but not to animals. Glyphosate is the major ingredient in Monsanto's RoundUp®, which has been marketed since 1973. In September 2000, Monsanto's patent on glyphosate expired and several other companies began offering glyphosate-based products. As of 2007, over 200 million pounds of glyphosate a year are sprayed in the United States alone.

Glyphosate acts to inhibit the formation of the aromatic amino acids, like tyrosine and tryptophan, in plants. These amino acids are also essential for neurological function in animals, as they are the precursors for neurotransmitters like dopamine and serotonin. Since glyphosate targets a synthetic pathway that is only present in plants, it was thought to be nontoxic to animals. Indeed, many studies have shown the direct toxicity of glyphosate to animals to be well within the acceptable limits. In addition, the majority of scientific investigation into potential carcinogenicity has also shown it to be safe. However, this research is not without legitimate criticisms.

Despite the controversy, the EPA maintains that glyphosate is safe for use at current levels. What is more, the EPA recently expanded the range of crops upon which glyphosate can be used, and is on the verge of increasing the tolerance levels which are used to determine how much can be found in food. (See Docket ID: EPA-HQ-OPP-2012-0132.)

Enter Genetically Modified Organisms (GMOs)

While genetically modified crops, like the Flavr Savr tomato, had already been around before Monsanto's foray into the GMO world, what made their entrance unique- and wildly successful- was the introduction of Roundup® Ready crops. In a nutshell, Monsanto scientists were able to engineer crops- particularly corn and soy- that were more resistant to glyphosate. This meant that higher amounts of glyphosate could be sprayed on the crops in order to control the weeds, without causing harm to the crop itself.

A second major innovation involved the insertion of genetic material from a soil bacterium known as Bacillus thuringiensis into corn which allows the plant to produce an insecticide known as Bt toxin. Also known as Cry toxin, when Bt enters the gut of an insect it causes the lining of their gut to break down, allowing for admission of Bt spores into the general circulation. Because Bt toxin is known to be very species specific, it was thought to be an excellent candidate for targeted genetic modification that, was also deemed to be safe for humans in the general body of research available.

The Method is the Madness

People who are not trained in scientific methodology often, quite understandably, have little awareness of how we go about "proving" that certain things are safe and/or effective. The most fundamental thing to understand is that we hardly- if ever- test these things directly. Science relies upon models which are thought to be close representations of what actually occurs in the human body. Over many decades, these models have been refined and have come to be generally accepted among the scientific community. Beyond this, government agencies like the USDA, EPA, and FDA, have come to rely upon these "gold standard" models when making policy decisions that impact public health.

The public, in turn, invests our faith in these government agencies to make decisions on our behalf, based upon the information they receive from the scientific community. When decisions get made that impact out everyday lives at the most fundamental level- for example food production- there is an immense amount of inertia generated around these policies. They become enshrined within our very laws which govern the land.

However, the perennial Achilles Heel of science is that we do not know what we do not know. That is to say- when models are created and developed, they are necessarily restricted by whatever information is available. Every so often, new information becomes available which calls the original model into question. When this occurs, we are required to go back and re-evaluate all the other information which has been extracted from a particular model in light of the new information.

This is what, I believe, has occurred with the standard models of toxicology and carcinogenicity used to evaluate the safety of substances entering our food supply. Yet, we are concurrently faced with the massive snowball effect generated by nearly a century of time of industrial practices and public policy moving in a particular direction. Moreover, this is compounded with a skyrocketing global population which means more mouths to feed. In many ways, the world has come to rely upon policies and practices being developed in the United States over the past decades.

Nobody Thought to Check Gut Bacteria

Back when we embarked upon this journey toward "modern" farming practices, very little was known about symbiotic bacteria in the human gut microbiome. Therefore, nobody thought to investigate the potential effects of compounds on gut bacteria. We just plain didn't look.

Since that time, and particularly in the last decade, research into the human gut microbiome has exploded. We now know that symbiotic gut bacteria play an integral role in the health of the human body. According to some estimates, approximately 90% of the DNA which is found in the human body is not human at all. Rather it is bacterial DNA. What is more, certain metabolic activities of these symbiotic bacteria are known to provide critical services to the functions of the immune, endocrine, and neurological systems.

We are only just beginning to understand how far-reaching and profound these implications are with respect to our understanding of health and disease. We have barely even begun to learn about the effects of chemicals like glyphosate and Bt toxin on gut bacteria, and through these, to the rest of the human body. But the preliminary data does not inspire much faith in our current trajectory with respect to GMO crops, in particular corn, soy, and cotton.

Research Makes a Turn

Around May 2011, new research began to surface which began to undermine the decades-old body of information which indicated that chemicals like Bt toxin and glyphosate were safe for human consumption. A study looking at pregnant women living in Quebec found pesticides associated to GMO foods present within both the women and their developing fetuses. This line of research eventually led to the banning of Bt corn in Germany, despite harsh criticism from other members of the scientific community. A more recent, but equally controversial, study showed a negative impact on bone marrow cell proliferation in mice.

A different strain of research, investigating the increase of Clostridia infection of cows in Germany suggests this phenomemon may be due to a toxic effect to beneficial gut bacteria called Enterococcus, which are the natural competitors of Clostridia in the gut microbiome. Similar effects were found in chickens, suggesting that disturbances in the balance of gut microbiota could explain the increased susceptibility to infections observed in these animals. That glyphosate is being found toxic to gut bacteria should not come as a complete surprise, as toxic effects on similar bacteria in the soil have been known about for almost twenty years.

More recently, a number of hypotheses linking a number of biochemical effects of glyphosate to disturbances in the gut microbiota, which in turn may contribute to a whole host of other chronic diseases, were put forth in the open-access journal, Entropy.

Is Banning GMO Crops the Solution?

While these findings are intriguing, and certainly deserve greater attention, the potential for this information to completely overturn several decades of agricultural policy means that it will be met with great skepticism from the scientific community at large, as well as from regulatory agencies, such as the EPA, which have been reaffirming the safety of glyphosate for a considerable time.

Nevertheless, a grass-roots movememt to label GMO foods is gaining widespread popularity. In May 2013, over 300 "March Against Monsanto" events were held around the world in order to raise awareness about the emerging risks associated with GMO crops. While Monsanto has been taking the brunt of the anti-GMO movement, having already fallen into disfavor for its aggressive policing of its intellectual property rights, they are not the only ones developing genetically modified crops. In 2014, the patent for Monsanto's Roundup® soybean seeds will expire. This will be the first patent expiration on a widely used bioengineered crop, and no doubt there are many companies right now preparing for launch of their own similar products.

Currently, 27 countries have banned GMOs, and 50 require labeling. Meanhile, in the United States, a move being labeled the "Monsanto Protection Act 2.0" involves an amendment to the Farm Bill which would prohibit States from passing GMO labeling laws. The movement against GMOs and companies like Monsanto is fiery, but is also being met with fierce opposition, and even ridicule. To be fair, it would appear that no legitimate movement comes without some elements of ridiculousness.

"Like" My Status

Social media has rapidly become a tremendous force for political change. It is also a trememdous force for misinformation, and outright propaganda. The challenge is when government agencies are trying to respond to various claims flying around, they have no place to turn but to the same experts who have been telling them all along that products like glyphosate are completely safe to use. None of these people want to deal with the potential fallout of having to admit they've been wrong this whole time.

While everybody has a right to voice their opinion, public opinion alone does not generate change when we fail to differentiate between what is opinion, and what is fact. Or speculation. Or even to acknowledge that there is a difference between any of these.

In my opinion, people have a right to have full transparency with respect to food production, and this includes GMO labeling. Moreover, I believe that the emergence of new scientific information has raised urgent questions about the validity of the models that the agricultural industry and regulatory agencies have been using thus far. This information suggests that the herbicide compound glyphosate may pose a substantial risk of harm to symbiotic microbiota growing within human beings and livestock. In addition, there is evidence to believe that glyphosate use presents a possible risk to nitrogen-fixing soil bacteria, upon which much of the global agricultural system relies. Finally, several demographic data sets suggest a possible correlation between the incidence of several chronic diseases and glyphosate use. I believe these questions are severe enough to warrant a full moratorium on any regulations allowing for the expanded use of glyphosate and/or the increase of allowable exposure levels to the public, and to livestock, while these potential effects are further investigated.

As we exercise our right to voice our opinions, let us also allow them to be guided by facts, rather than accusations. People don't tend to respond well to accusations, whether or not they are true. Besides, in the end it's just not the easiest way to get something done.

Journal References

Aris A, Leblanc S. Maternal and fetal exposure to pesticides associated to genetically modified foods in Eastern Townships of Quebec, Canada. Reprod Toxicol. 2011 May;31(4):528-33. doi: 10.1016/j.reprotox.2011.02.004

Kruger M, Shehata AA, Schrodl W, Rodloff A. Glyphosate suppresses the antagonistic effect of Enterococcus spp. on Clostridium botulinum. Anaerobe. 2013 Apr;20:74-8. doi: 10.1016/j.anaerobe.2013.01.005

Samsel A, Seneff S. Glyphosate's Suppression of Cytochrome P450 Enzymes and Amino Acid Biosynthesis by the Gut Microbiome: Pathways to Modern Diseases. Entropy. 2013; 15(4):1416-1463. doi: 10.3390/e15041416

Santos, A. and Flores, M. (1995) Effects of glyphosate on nitrogen fixation of free-living heterotrophic bacteria. Letters in Applied Microbiology. 20: 349-352. doi: 10.1111/j.1472-765X.1995.tb01318.x

Shehata AA, Schrodl W, Aldin AA, Hafez HM, Kruger M. The effect of glyphosate on potential pathogens and beneficial members of poultry microbiota in vitro. Curr Microbiol. 2013 Apr;66(4):350-8. doi: 10.1007/s00284-012-0277-2

Last Updated: 24 Aug 13