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The GMO Food Debate – Beyond the Gut Microbiome

A few days ago I wrote a post about potential impacts of GMO foods on the gut microbiome. Today, I wanted to talk a little bit more about the GMO food debate and my thoughts about other issues that surround this topic.

Plant and Insect Resistance

Glyphosate
Some argue that genetic modification, like that used in the development of Roundup-ready soybeans and corn, is just a way of speeding up a natural process. The idea here is that, if the plants were exposed to glyphosate (the active ingredient in Roundup) over a long period of time, they would naturally develop resistance to the herbicide.

This is absolutely true and is exactly what’s happening. But there’s one problem: it’s happening in the plants that glyphosate is intended to kill. What does this mean exactly?

Farmers, despite spraying enormous amounts of glyphosate on their crops, are still dealing with overgrowths of weeds in their fields. This really shouldn’t come as a surprise. Plants are extremely resilient and adaptive, as are the symbiotic bacteria that live within and around those plants. Though I don’t know exactly what’s happening, I wouldn’t be surprised if there were some type of commensal bacteria that are assisting the plant in the ability to metabolize and detoxify glyphosate.

Naturally, the solution is to create another transgenic plant that is resistant to a different (and more toxic) herbicide. That will fix all of our problems, right? Ok, probably not. But this is where industrial agriculture is headed.

In light of the fact that Roundup no longer appears to be working as an effective herbicide, genetically modified plants that are resistant to 2,4-D were just approved for agricultural use. As far as I’m concerned, this is a huge problem. If this plays out anything like the ‘Roundup-ready’ crops, we will see a dramatic increase in the use of 2,4-D and likely a corresponding rise in negative consequences for humans and the environmental.

2,4-D
We’ve already seen what happens when an herbicide is used in large amounts and in regular intervals. Weeds in industrial crops have been exposed to large amounts of glyphosate. This has created an intense selective pressure, forcing these plants to develop survival mechanisms in the face of toxin overload. There is no reason to believe that 2,4-D exposure will be any different.

There is already research showing that endophytes (bacteria that live within plants) can help plants detoxify 2,4-D for use in phytoremediation. Meaning that some plants, and their associated bacteria, already possess resistance to 2,4-D (incidentally, can someone please tell me why we are trying to increase the use of an herbicide that is toxic enough that we are currently in the process of trying to remove it from the environment?).

Already, 16 species of plants worldwide are known to be resistant to 2,4-D. I strongly believe that it is really only a matter of time before agricultural “weeds” develop tolerance to 2,4-D*. Especially if they are sprayed on a constant basis. At which point we are left with highly contaminated soil, air, water, and bodies. And the industrial farming industry is still left looking for the ever elusive magic bullet for mass production of toxic food-like products with minimal physical input.

[*But really, don’t worry. According to their most recent news release, the EPA has put measures into place to “ensure that weeds will not become resistant to 2,4-D.” Color me skeptical.]

Bacillus thuringiensis (Bt)
Bt is a naturally-occurring soil bacterium. It has insecticidal toxins and has been a popular tool in organic farmers for over 50 years. Genetically modified Bt crops were introduced in 1996, with the goal of decreasing the use of pesticides on crops. Through genetic modification, genes from Bt are inserted into certain crop plants (namely cotton and corn). The plants are then resistant to certain pests because they are capable of producing the insecticidal toxin without the application of any additional pesticides. When those pests eat the crops, they stop eating within a couple of hours and die shortly thereafter.

When genetically modified Bt crops were first introduced, it was with the caveat that farmers needed to provide a “refuge” – a section of non-GMO crops adjacent to their GMO crops. These could be in the form of strips, borders, or blocks. The goal was to reduce the rate at which insects would develop resistance to the Bt crops. Up until about 2005, compliance was close to 100%. In the last 6 years, however, fewer than 75% of farmers using Bt crops also planted non-GMO refuge crops.

The result is a rise in the number and types of pests that are resistant to Bt application and Bt crops. Pests were already developing resistance to Bt toxin, but the lapse in compliance and regulation are likely worsening the problem. Even 30 years ago, before the introduction of GMO Bt crops, researchers demonstrated the development of insect resistance to Bt. Now that Bt crops have been around for close to 20 years, more resistance is cropping up. Particularly concerning for farmers is the development of Bt resistance in pests the crops were designed to kill.

Toxicity to Humans, Plants, and Wildlife

The ‘innocent until proven guilty’ philosophy, as applied to our food system, is a flawed one. Partly because it is so difficult to “prove” that something is harmful in agricultural use, and partly because it can take a very long time for negative effects to show up, it is very hard to anticipate what the true impacts will be of herbicides, pesticides, and potentially GMO foods. What’s even more bizarre and worrisome is that, even when we know that particular chemicals directly contribute to severe health problems, it is extremely difficult to stop companies from using those substances in the food system.

Glyphosate
Roundup is touted as the “safest” herbicide ever invented. Ok, sure. Awesome. Except for the fact that “safest” says nothing about baseline toxicity. As I mentioned in my last post, we already know that Roundup is toxic to bacteria, including the gut bacteria that are crucial for our overall health. There is also evidence that exposure to Roundup may promote reproductive problems, birth defects, and DNA damage that could lead to increased cancer risk.

Glyphosate has also been shown to be toxic to ectomycorrhizal fungi (EcM). These are a type of fungi that form symbiotic relationships with plants, helping protect and nourish the plant host. EcM are important to the survival of many plant species and if herbicides inhibit growth of ectomycorrhizae, wild plants could experience even more damage than they would from glyphosate exposure alone.

But the bigger issue is this: If we have exhausted our ability to use the “safest” herbicide ever invented, where do we go from here? To the “second safest”? What about after that? No matter which way you look at it, there doesn’t seem to be a great place to go at this point. At least not if we continue down the path of “let’s create more GMOs so we can use more and different herbicides and pesticides”.

2,4-D
Now that 2,4-D-resistant plants have been approved for agricultural use, application of the herbicide is expected to increase from current rates of 30 million pounds to over 100 million pounds in the next 10 years. It’s difficult to comprehend and nearly impossible to predict exactly what that will mean in terms of human health and environmental effects. But I can see very little evidence that any of the direct outcomes related to increased 2,4-D use will be positive.

We already have some indication as to the negative health implications of 2,4-D exposure. We are talking about severe, life-threatening illnesses. 2,4-D exposure is strongly associated non-Hodgkin’s lymphoma (cancer of the white blood cells). Studies in animals show that both hormone and neurotransmitter function are disrupted, resulting in serious impacts on infant development and increased rates of birth defects and neurological damage.

The EPA lists toxicity to the eye, thyroid, kidney, adrenals, and ovaries/testes, as well as neurotoxicity and developmental toxicity, as effects of exposure to high doses of 2,4-D. That’s a pretty long list of severe health maladies. And it probably isn’t exhaustive, as the EPA tends to be conservative when it comes to estimating risks.

Farm workers are very likely the most at risk for 2,4-D toxicity, but they aren’t the only people who need to be concerned about exposure.

[Slight tangent: Several active ingredients in chemical sunscreens increase the amount of 2,4-D that is absorbed into the skin. So, farm workers might be uniquely susceptible to the toxic effects 2,4-D, as they are generally encouraged to wear sunscreen due to the long hours they spend in the sun. One more reason not to use chemical sunscreens.]

A large study was conducted, in which low concentrations of 2,4-D were detected in the urine collected from Americans of all age groups. It seems that there are several possible routes of exposure. 2,4-D penetrates the leaves of plants, which may mean that it is still present in plants that are treated with the herbicide. Regulatory monitoring by the USDA has not shown detectable toxic levels of 2,4-D in food residue, but that doesn’t rule out the possibility that it could be present in some foods. Particularly if application ramps up in the next several years. The herbicide has been detected in drinking water, though at levels below the maximum contaminant level set by the EPA.

The relatively low levels in both food and water may largely be due to the fact that 2,4-D isn’t that heavily used at the moment. That will almost certainly change once 2,4-D resistant crops are put into use. Currently, about 30 million pounds of 2,4-D is currently applied to crops each year. Compare that to 185 million pounds/year of glyphosate (as of 2007), which is found in relatively high levels in food. If, as predicted, annual 2,4-D application increases to over 100 million pounds/year it is reasonable to expect that 2,4-D residues in food will increase in kind.

2,4-D is also toxic to wildlife and plants. Birds, fish, and aquatic (water-based) invertebrates such as worms, crabs, and starfish are all susceptible to the herbicide. Unsurprisingly, 2,4-D is highly toxic to both aquatic and terrestrial (land-based) plants. Runoff from farms contaminates land and waterways, killing off endangered species and reducing overall biodiversity of both plants and animals. As use of 2,4-D increases, so will the negative health and environmental impacts.

[Slight tangent #2: ‘Maximum contaminant levels’ have been developed for about a zillion different potential contaminants. But what about the effects of interactions between different toxicants? For example, there is evidence that Bt crops treated with Roundup are more toxic than either one alone. The fact that interactions are not accounted for is worrisome and, as far as I’m concerned, in some ways nullifies the whole idea of a maximum contaminant level.]

Don’t Forget About the Bugs

Monarch Butterflies and Other Insects
One of the biggest sources of controversy over the use of Bt crops is the potential impact on Monarch butterflies. Toxicity of Bt crops is not limited to plant tissues, and pollen of the crops is also toxic. With toxic pollen comes damage to pollinator species such as butterflies, wasps, and potentially bees.

It has also become apparent that many species of caterpillars might be affected by Bt corn. Monarch butterflies have received the brunt of the concern and resulting research. However, there is evidence that larvae from other butterfly species are also at risk. Because there is little motivation for researching the effects of Bt crops on all vulnerable insect species, it is impossible to know the true extent of the effects on pollinators.

I’m not suggesting that widespread insecticide application is superior to the use of Bt crops. But I do think it’s important to have a full understanding of the consequences of different agricultural strategies. Additionally, just because one option is better than another does not necessarily make it the best option.

Bees?
Colony collapse disorder (CCD) has had a good deal of press in the last several years. CCD is a perplexing phenomenon in which honeybees abruptly abandon hives that are fully functional and have plenty of food. The honeybees require the warmth of the hive and the food stores in order to survive the winter. When they leave the hive, they die. The jury is still out as to the cause, but there is increasing evidence that systemic pesticides in genetically engineered could be at least partially to blame.

Specifically, neonicotinoid insecticides (neonics) have come under scrutiny in the last 8-10 years. This class of insecticides is neuroactive, meaning that they target the nervous system in order to kill insects. In 2004, a corn-seed treatment program began, in which genetically engineered seeds were treated with a neonicotinoid insecticide. Pollen from plants grown from these seeds had high levels of the insecticide, even when the plants themselves weren’t treated with it.

Several studies have been published in the past few years implicating systemic neonics as the cause of CCD. Based on their findings, researchers suggest that insecticide residues, like those found in the pollen of GMO neonicotinoid plants, act as neurotoxins to honeybees and cause them to display unusual, self-harming behavior like that found in CCD. As always, there is still a bit of controversy with regard to these findings, and it is unlikely that neonics are solely responsible for CCD. But the evidence is strong enough to suspect that they do play some role, and the relationship is certainly worth investigating further.

Final Thoughts

There comes a point where trying to constantly fight nature isn’t going to work any more. We’re essentially dealing with a series of stopgap measures, with no real concept of what a permanent solution might be. Strategies like integrated pest management (IPM) offer some ideas for how to prevent crop damage without the use of chemical application. There is a great deal of evidence that techniques such as organic farming and IPM are economically viable. They also preserve the land in a way that is impossible with the current state of industrial agriculture.

Sustainability is key, and massive chemical use, facilitated by the development of genetically modified crops, is just about as far from sustainable agriculture as we can get. At some point we will be forced to work with the natural world on a large scale. I just hope, for the sake of our health as humans and the health of the environment, that we start to work with nature sooner rather than later.

Resources:

Benbrook, C. (2012). Impacts of genetically engineered crops on pesticide use in the U.S. — The first sixteen years. Environmental Sciences Europe, 24(24).

Benbrook, C. (2012). The good, the bad, and the ugly: Impacts of GE crops in the United States.

Bohn et al. (2014). Compositional differences in soybeans on the market: Glyphosate accumulates in Roundup Ready GM soybeans. Food Chemistry, 153, 207-215.

Beuret et al. (2005). Effect of the herbicide glyphosate on liver lipoperoxidation in pregnant rats and their fetuses. Reproductive Toxicology, 19(4), 501-504.

Egan et al. (2011). 2,4-Dichlorophenoxyacetic acid (2,4-D) – resistant crops and the potential for evolution of 2,4-D – resistant weeds. PNAS, 108(11).

Estok et al. (1989). Effects of the herbicides 2,4-D, glyphosate, hexazinone, and triclopyr on the growth of three species of ectomycorrhizal fungi. Bulletin of Environmental Contamination and Toxicology, 42, 835-839.

Figgs et al. (2000). Increased lymphocyte replicative index following 2,4-Dichlorophenoxyacetic acid herbicide exposure. Cancer Causes and Control, 11(4), 373-380.

Germaine et al. (2006). Bacterial endophyte-enhanced phytoremediation of the organochlorine herbicide 2,4-Dichlorophenoxyacetic acid. FEMS Microbial Ecology, 57(2), 302-310.

Gunning et al. (2005). New resistance mechanism in Helicoverpa armigera threatens transgenic crops expressing Bacillus thuringiensis Cry1Ac toxin. Applied and Environmental Microbiology, 71(5), 2558-2563.

http://npic.orst.edu/factsheets/2,4-DTech.pdf

http://www.bt.ucsd.edu/gmo.html

http://www.epa.gov/opp00001/pestsales/07pestsales/market_estimates2007.pdf

http://www.epa.gov/oppsrrd1/REDs/factsheets/24d_fs.htm

http://www.ext.colostate.edu/pubs/crops/00707.html

http://yosemite.epa.gov/opa/admpress.nsf/d0cf6618525a9efb85257359003fb69d/72fde554930f3f6985257d7200591180!opendocument

Koller et al. (2012). Cytotoxic and DNA-damaging properties of glyphosate and Roundup in human-derived buccal epithelial cells. Archives of Toxicology, 86(5), 805-813.

Lu et al. (2005). In situ replication of honey bee colony collapse disorder. Bulletin of Insectology, 65(1), 99-106.

McGaughey, W. (1985). Insect resistance to the biological insecticide Bacillus thuringiensis. Science, 229(4709), 193-195.

Miligi et al. (2006). Cancer and pesticides: An overview and some results of the Italian multicenter case-control study on hematolymphopoietic malignancies. NY Academy of Science, 1076, 366-377.

Paganelli et al. (2010). Glyphosate-based herbicides produce teratogenic effects on vertebrates by impairing retinoic acid signaling. Chemical Research in Toxicology, 23(10), 1586-1595.

Pont, A. et al. (2004). Active ingredients in sunscreens act as topical penetration enhancers for the herbicide 2,4-Dichlorophenoxyacetic acid. Toxicology and Applied Pharmacology, 195(3), 348-354.

Richard et al. (2005). Differential effects of glyphosate and Roundup on human placental cells and aromatase. Environmental Health Perspectives, 113(6), 716-720.

Tabashnik, B. (1994). Evolution of resistance to Bacillus thuringiensis. Annual Reviews in Entomology, 39, 47-79.

Zahn et al. (1990). A case-control study of non-Hodgkin’s lymphoma and the herbicide 2,4-Dichlorophenoxyacetic acid in Eastern Nebraska. Epidemiology, 1(5), 349-356.

**I would like to point out that I am not inherently opposed to genetic modification of plants. I think there is some promising research showing that the use of GE plants can improve rates and effectiveness of phytoremediation. In those cases, increased use of pesticides and herbicides is not required and the goal of genetic modification is clean up the earth rather than to kill things. I do, however, inherently oppose any technology that contributes to an increase in pesticide and herbicide application, or that is clearly detrimental to human and environmental health. Unfortunately, most GMO food crops have severe negative effects on the planet. At the very least, I think people should be equipped with the knowledge necessary to avoid those food products if so desired.



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