GMOs and Human Health: GMOs Part IV

Sweet corn after silk emergence. (USDA)

GMOs and Human Health:  GMOs Part IV

The following excerpt is from the Penn State Ag Science Magazine Spring/Summer 2015 Edition.

Ask just about any scientist if GMOs are bad for our health and he or she will say, “Probably not.” That’s because no reputable studies have shown any negative health effects of eating GMOs. And scientists around the world continue to look for any evidence of risk or unintended consequences.

“Europe is famous for being the place with the greatest objection to GM crops, so I think it’s instructive that the European Union spent nearly $300 million to study the impacts of GMOs, and what they concluded was that essentially there is no substantial difference between GM and non-GM crops in terms of either food safety or environmental impact,” said Roush.

Indeed, the EU report, published in 2010, stated, “The main conclusion to be drawn from the efforts of more than 130 research projects, covering a period of more than 25 years of research, and involving more than 500 independent research groups, is that biotechnology, and in particular GMOs, are not per se more risky than e.g. conventional plant breeding technologies (1).”

A separate review of the scientific literature published in 2014 examined animal health in particular. The review examined data on over 100 billion animals following the introduction of GM foods and found no “unfavorable or perturbed trends in livestock health and productivity (2).” In fact, during the period studied, animal health and growth efficiency actually improved.

Ott noted that some of the concern about the health effects of GMOs may be due to a study—which was flawed and later retracted—claiming that feeding GM corn to mice caused them to develop tumors. However, he said, much of the concern is generated from claims of risks found ubiquitously on the Internet and social media posted by individuals opposing the use of the technology or by people selling non-GM foods.

Beyond actually ingesting GM foods, some people worry that the genes inserted into GMOs could “jump” out of target plants or animals and into other organisms. Indeed, “horizontal gene transfer”—the transfer of genetic material from one organism to another without reproduction or human intervention—is a real phenomenon, one that has occurred in nature since the beginning of life on Earth. For example, scientists have known for some time that natural insertion of genetic material from viruses into the human genome is responsible for a significant proportion of cancers (3). Yet, a review article published in 2008 noted that the risk of horizontal gene transfer from GM plants to human health or the environment is negligible (4).

When it comes to the health risks of GMOs themselves, Mortensen believes there is science yet to be done that could reveal more compelling evidence of health effects. “When we do science, if we do it well, it is objective, but the science that we choose to do is subjective,” he said, suggesting that perhaps the right questions have not yet been asked. But data do exist indicating that the herbicides used on GM crops may have negative health effects. “GM seeds do not exist in isolation, but rather are sold alongside pesticides, which they are designed to resist,” said Mortensen. “Using a technology that results in a clear and deliberate intended increase in the use of pesticides, some of which have negative health effects associated with them, and very clear ones, well there are clear health downsides to that.”

Glyphosate is the most commonly used herbicide and is applied to Roundup Ready crops, including soy, corn, canola, alfalfa, cotton, and sorghum. Most people agree that the health effects of glyphosate are not as severe as some of the other pesticides in use. However, there is not universal agreement on this issue. “The health effects of exposure to glyphosate are not clear,” said Mortensen, “but I don’t think there is compelling data to indicate that the herbicide is dangerous.”

Roush too believes that glyphosate is “arguably the safest herbicide ever developed. It is so safe that we let people buy it in grocery stores and take it home and spray it in their gardens,” he said. “Its toxicity is on the order of salt.”

  1. A Decade of EU-Funded GMO Research. 2010.
  2. Van Eenennaam, A.L., and A. E. Young. 2014. Prevalence and impacts of genetically engineered feedstuffs on livestock populations. Journal of Animal Science 92(10): 4255–4278.
  3. Riley, D.R., et al. 2013. Bacteria-human somatic cell lateral gene transfer is enriched in cancer samples. PLOS Computational Biology 9(6): e1003107.
  4. Keese, P. 2008. Risks from GMOs due to horizontal gene transfer. Environmental Biosafety Research 7: 123–149.
  5. Mortensen, D.A., J.F. Egan, B.D. Maxwell, M.R. Ryan, and R.G. Smith. 2012. Navigating a critical juncture for sustainable weed management. BioScience 62: 75–84.
  6. Registration of Enlist Duo. U.S. Environmental Protection Agency.
  7. Schinasi, L., and M.E. Leon. 2014. Non-Hodgkin lymphoma and occupational exposure to agricultural pesticide chemical groups and active ingredients: A systematic review and meta-analysis. International Journal of Environmental Research and Public Health 11(4): 4449–4527.
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