Genetically Modified Organisms and Potential Human Health Impacts

Renee Bouldin Natural Resource Conservation, Eric Herrmann Environmental Science, and Aliza Yaillen Animal Science

According to the United Nations, the world’s population is increasing by 110,000 people each day (United Nations, 2015). We are continuously bombarded with images of starving children and questions about our long term food sources. How can we possibly expect to feed 11.2 billion people, the United Nation’s estimated world population by the year 2100 (2015), when we already know that there are already so many starving people in the world?  Especially when there are pressing concerns about land and water availability, necessary growing conditions, and costs. As world population skyrockets, more food needs to be grown to meet the increased demand.

Scientists considered genetically modified organisms (GMO) as a panacea to the impending global food shortage. They were meant to grow more food while taking up less space. Certain modifications even promised to reduce the need for frequent herbicide applications (Wilkerson, 2015). It has become customary in the United States to rely on genetic modification to meet our food demands and reduce our reliance on herbicides that remove weeds using chemicals (National Academies of Science, 2016).

Yet, somewhere in the political rhetoric and confusing online articles, a mistrust of genetic modification developed. A genetically modified organism (GMO) is an organism, such as a plant, that is “manipulate[d]…by introducing new genes…and transferring genes between different organisms” (Genetic Science Learning Center, 2013). While several people believe that GMOs are unsafe to eat, this modification of organisms does not inherently lead to dangerous human health impacts.

There are several studies that compare genetically modified organisms to conventional crops grown without modification that substantiate this claim. These studies show little to no significant differences in nutritional values. In a study by Silva et al. (2016), genetically modified (GM) tomatoes had no major differences when compared to non-GM tomatoes. In another study, Chang et al. (2012) observed no differences between GM rice and non-GM rice, only finding minor changes in metabolite concentrations caused by gene modification (p. 484). Le Gall, Colquhoun, Davis, Collins and Verhoeyen (2003) and Venneria et al. (2008) also discovered no differences in protein content, acid content, or mineral content of GM wheat, corn, and tomatoes and their respective non-GM controls. Although a few studies found significant differences, “natural variability” (Frank et al., 2016, p. 3005) rather than genetic modifications, were often attributed as having the greatest effect on nutritional variations. Genetic modification did not cause the variability of nutritional values between GM versus non-GM.  Rather, the differences occurred naturally and would have happened regardless of human interference and genetic modification.

Most importantly, these genetically modified crops did not affect the health of animal test subjects compared to those given conventional feed. A study by Korwin-Kossakowska, Sartowska, Tomczyk, Prusak and Sender (2016) tested different feeds of GM soy and maize compared to conventional controls on quail.  They found “no negative effect of the use of GM [food]…with regard to bird health status…” (Korwin-Kossakowska et al., 2016, p. 415).

Furthermore, autopsied birds showed no indication of the “existence of the pathological changes caused by pathogens, nutritional factors or of environmental nature” (Korwin-Kossakowska et al., 2016, p. 415). Similarly, Hammed et al. (2016) found no influence of GM sugar cane on chickens compared to control groups fed non-GM feed. Finally, Yuan et al. (2013) studied the effects of rats and GM rice and discovered no adverse effects on the rats’ gastrointestinal tracts, or other nutrient variations. Therefore purely modifying an organism’s genes does not directly lead to negative health repercussions.  

However, different versions of GMOs do exist. Some genetic modifications simply modify the crop to meet environmental growing conditions. For example to use less water, withstand tougher conditions, or produce higher yields (National Academies of Science, 2016). Other genetic engineering is designed to help crops resist herbicides (Hanson et al., 2013). Both types of GMOs, by themselves, do not alter the nutritional values of the crops or cause direct human health impacts. However, herbicide resistant GMOs present several other problems that can potentially lead to dangerous effects to human health.  

Herbicides are widely used in agricultural production to prevent or control weeds in an effort to reduce or eliminate yield losses and maintain high product quality (Hanson et al., 2013). One type of herbicide resistant GMO displays a tolerance to the herbicide glyphosate, otherwise known by its brand name Roundup (Wilkerson, 2015). This simplifies weed management for farmers by allowing them to spray heavier doses of herbicides without damaging their crops (Landrigan & Benbrook, 2015).  However, the chemicals used in herbicides may cause detrimental health effects in humans (National Pesticide Information Center, 2015).

Making its retail debut in 1974, glyphosate [N-(phosphonomethyl) glycine], or Roundup,  steadily gained popularity in the American market by boasting its efficiency in killing weeds at low cost, perceived low toxicity, rapid absorption by plants (Duke & Powles, 2008). Glyphosate acts as an inhibitor of an enzyme (Duke & Powles, 2008). This inhibition prevents plants from making the essential proteins they need to survive, thereby killing them (Wilkerson, 2015).

Roundup was also marketed as a low-toxicity herbicide that reduced environmental degradation from soil tillage (Duke & Powles, 2008). The primary reason to till land before planting was to mechanically destroy weeds, which is unnecessary when using Roundup (Wilkerson, 2015). Tillage can be harmful to the environment because it causes topsoil loss and runoff into surface water sources (Duke & Powles, 2008).

Because of these perceived benefits, the adoption of glyphosate resistant GMOs was extremely rapid (Duke & Powles, 2008). Over 90% of all US soybeans and almost 70% of cotton was glyphosate resistant by 2006, and “more than 80% of all GM crops planted worldwide are [glyphosate-resistant] crops” (Duke & Powles, 2008, p 322). This allows farmers to spray heavier doses of herbicides on their crops, reducing labor and equipment costs (Duke & Powles, 2008).

The benefits glyphosate resistant GMOs, often called Roundup Ready crops, are only valid when Roundup is the only herbicide used on a field (Hanson et al., 2013). However, it is well known by scientists that only spraying one herbicide has a strong potential to push weeds to develop a resistance to it (Wilkerson, 2015). Genetic resistance to glyphosate occurs when a weed has a mutation that allows it to survive Roundup spraying (Hanson et al., 2013). If the resistant weed reproduces, it can pass the mutation on to offspring, who will also survive Roundup applications (Hanson et al., 2013). This may then lead to clusters of “superweeds” (Wilkerson, 2015) that render Roundup ineffective.

There are already 24 documented cases of Roundup resistant weeds around the world, 14 in the United States alone (Hanson, et al., 2013). These so called “superweeds,” now require a different herbicide to be used on them, or an increased amounts of Roundup to be killed (Harmon et al., 2013). These increased applications are likely responsible for increases of glyphosate detected in GM foods.

Increased applications of glyphosate can lead to increased human exposure to glyphosate, which in turn can lead to glyphosate detected in the body. A study by Guyton et al. (2015) that showed individuals exposed to very high concentrations of glyphosate short term (typically agricultural workers), contained detectable amounts of glyphosate in their blood and urine. This was an indication that the chemical was absorbed into their bodies (Guyton et al., 2015). We saw the results mirrored in a study that tested exposure to chemicals found in herbicides associated with genetically modified foods in pregnant and nonpregnant women. Aris and Leblanc (2011) detected glyphosate in the bloodstream of some nonpregnant women they tested.

Research done by Conrad et al. (2016) followed a town in Germany over a fifteen year period. They examined the amount of glyphosate consumed to see the effects of the herbicide and the effects of exposure (Conrad et al., 2016). The results showed that in 2001, the percentage of glyphosate detectable in people’s urine was only 10%, but then went up significantly in 2012 and 2013 to above 50% (Conrad et al., 2016). In 2015, Conrad et al. (2016) observed that the percentage was down to 40%. They attributed these results to the reduced amount of herbicide used on crops grown throughout Germany (Conrad et al., 2016).  As each person consumed their normal diet, the researchers also looked over how much glyphosate was sprayed on the plants. The percentages correlated with the fact that the more glyphosate that was sprayed, the more glyphosate that was consumed, and thus detectable in each person (Conrad et al., 2016).  

Therefore it is possible for humans to uptake glyphosate from consuming Roundup Ready foods. Concerningly, Spiroux and Vendomois et al. (2010) found Roundup residues present in more than 80% of edible cultivated GMOs (p. 597). These chemicals are present in food slotted for human consumption. But why should this matter?

The real danger with glyphosate lies in the uncertainty of the effects it may have on the human body. Glyphosate, according to the National Pesticide Information Center (2015), can be very dangerous when consumed in large doses. The National Pesticide Information Center (2015) also expressed that glyphosate is shown to have carcinogenic potential and therefore may lead to cancers such as non-Hodgkin lymphoma.

There is also data to support that glyphosate-based herbicides present “DNA damages and CMR effects on human cells in vivo” (Gasniera et al., 2009, p. 190). This means they observed carcinogenic, mutagenic, or reprotoxic (CMR) effects in living organisms (in vivo) when exposed to these herbicides.  This claim is backed by a similar study that found “glyphosate and glyphosate formulations induced DNA and chromosomal damage in mammals, and in human and animal cells in vitro” (Guyton et al., 2015, p. 491).

While the detections in food, so far, may not be at levels high enough to cause some of these detrimental health effects, they are still quite alarming. However we are uncertain of exactly how much glyphosate is in our food, due to inadequate testing.

Overall we’ve found that genetic modification intended to alter crops for improved growth or enhanced nutritional values are not necessarily dangerous to consume. However, when crops are genetically engineered to resist herbicides, this opens the door to increased herbicide applications which has the potential for human health impacts and a potential increase in food prices. Genetically engineering crops to be herbicide resistant may not be our best option for food production, but while we are using it, we need to make sure that the government is doing its job by checking the amount of herbicide present in food.

Data from the United States Geological Survey shows herbicide usage has increased in the United States since the introduction of GM crops in the mid-1990s (Hakim, 2016). As it goes up, there may be health impacts on humans and price increases of food, since an excessive amount of glyphosate is used. The Food and Drug Administration (FDA), a branch of the government, has the responsibility to make sure that our food is edible. The United States Government Accountability Office released a statement that said, “limitations in FDA’s methodology hamper its ability to determine the national incidence and level of pesticide [specifically glyphosate] residues in the foods it regulates, one of its [the FDA’s] stated objectives” (Food Safety, 2014).  The government was not able to determine the amount of pesticide in food that was being produced, sold, and eaten by people in our country.  

That is problematic due to our lack of understanding of what glyphosate has the potential to do to people once they are exposed. More testing, more often, is critical to determine the amount of glyphosate humans are consuming in this country. Although it may take more man power, and thus more money, it would be worth it to protect the health of American citizens. The government and the FDA need to make testing how much herbicide is being sprayed on plants a priority, and should invest money, and more people into this process.

Development of genetically modified crops presents a variety of problems that need to be solved. Unproven impacts of GMO use leave buyers and researchers skeptical and it is clear based on the data presented research needs to be performed to establish realistic limits to understand and control this “new” technology.  For now, a crucial step the government can do is test and track the amount of glyphosate being used in this country to ensure there will not be future health impacts on our population.


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