Nathan Daley, MD, MPH
You might ask, “why all the fuss about agricultural genetically modified organisms (GMOs)?” After all, regulatory agencies have approved these technologies for widespread application and consumption, so they must be safe, right? Well, the truth is that there is no agency and no industry that works to protect our health. At best, the EPA, USDA, and FDA attempt to respond to our disease after the cause is widespread. At that point only risk reduction, rather than risk avoidance, can be achieved. This has been the case historically with radium paint, tobacco, particulate air pollution, water pollution, asbestos, lead, food-borne illnesses, and DDT. A number of the various 80,000 chemicals in production will likely be added to this list in the future while the majority of them that actually do contribute to disease (often in combination and in complex ways) will never be scientifically associated with disease. This is because science is far from perfect, scientific methodology is always biased and often manipulated, and scientific interpretation by stakeholders and decision makers is alarmingly inept (I’m not being political or condescending, these are well known and easily observed facts).
The situation with agricultural GMOs is unique compared to other technologies. While genetic engineering of food crops has been ongoing for 15 years, it is currently experiencing a major boom with the potential for widespread worldwide application. Yet, few people understand how a GMO food could really be so much different than a non-GMO food in regard to health and disease effects. GMO foods look like non-GMO foods and so we don’t experience the same hesitation and aversion to consuming them like we would, say, a clearly labeled bottle of virus and pesticide in tomato juice. Therefore, the quality of public education, consumer awareness, and informed public discussion about this technology has the potential to alter the future of GMO agriculture for better or worse.
In this article, I’ll first briefly mention the relative paucity of risk assessment studies on GMOs and the unbelievable weaknesses of the industry studies that have been done. Then, drawing from numerous independent studies, I will explore the routes by which agricultural GMOs may cause adverse health effects.
GMOs Have Never Been “Proven” Safe
Let me be clear; despite the following negative review of industry science, this article is not a hatchet job against the agricultural GMO industry but, rather, a vehicle for consolidated scientific information on the safety or risks of GMO foods intended to allow readers to make informed choices about this technology. It is just that, well, the science coming from the industry tends to raise serious concerns and suggests that the agricultural GMO industry has little concern for protecting public and ecosystem health. Before we dive into the independent non-industry studies which suggest potential harm from GMO crops and foods, we must first look at the studies which supposedly demonstrate the safety of GMO crops and foods. A critique of these studies remained impossible for some time as the data was kept private, until French researchers obtained a court order for their release. This team of researchers, lead by Joel Spiroux de Vendomois, then analyzed the raw data from studies on three varieties of GMO corn owned by Monsanto. Yet, it immediately became apparent that this data was not extremely helpful as the study methodology was profoundly insufficient. In a 2010 paper published in the International Journal of Biological Sciences, the researchers summarize several major flaws in the study. I’ll list just a few of them here:
- For each of the three varieties of GMO corn tested, only a single study was done. However, a central tenet of sound science is that the results are reproducible and replicated by other studies, preferably those done by different researchers.
- Only the rat was used as a toxicological model. Rats are useful models for the human detoxification systems, but poor models for human reproductive and embryological systems. Remember, rat studies “proved” that thalidomide was safe for pregnant women to use… but the rabbit studies done AFTER thousands of babies were harmed “proved” that it caused birth defects! Scientific proof is only as good as the scientific studies, which are always limited and narrowly focused.
- The studies lasted only 3 months and were done on young adult rats. Yet, captive rats live about 24 months. No studies looking at late life outcomes from this brief exposure or studies which used lifelong exposure to GMOs were performed. This is clearly a problem unless human consumers are only supposed to eat GMO foods for no longer than 9 years between the ages of 10 and 20. Yet, GMO food technology has been released (without labeling) with the intention of lifelong consumption.
- No reproductive or developmental studies were done. Yet GMO foods do not carry a label declaring that their safety during pregnancy has not been evaluated. Instead, they are unlabeled and meant to be consumed by both genders, at all ages and developmental stages, including during pregnancy and infancy.
- Adverse outcomes were only considered if they occurred in both genders! Clearly genders are different. For instance, women are much more likely to get breast cancer than men, and one must have a prostate to get prostate cancer. In the industry studies, increases in prostate cancer in male rats and increases in mammary tumors in female rats would apparently have been omitted since they differed between genders. This explains exactly what happened to their findings that male rats eating GMO corn had an 11% increase in heart size while female rats eating GMO corn had a 40% increase in serum triglycerides. It is not clear what to make of these findings, but they should not have been omitted and, instead, should have been used to encourage more numerous and longer duration (lifespan) studies before the worldwide release of GMO corn.
- Adverse outcomes which are consider “normal” in old rats were omitted in this young rat population. For instance, the researchers did not consider “chronic progressive nephropathy”, a kidney disease common in older rats, to be a problem even though it was occurring in young, 5 month old, rats eating the GMO corn.
Now, I can attest that modern toxicology students training at respectable universities are taught to do much better work than this. We can only speculate about the reasons such limited study methodologies were chosen. Nonetheless, these are the studies which the FDA determined to be sufficient for the approval of the three GMO corn varieties represented. As if the major flaws in the study methodologies were not enough to warrant a different decision, the French team of researchers found a number of concerning associations upon re-analyzing the raw data. They summarize:
Our analysis clearly reveals for the 3 GMOs new side effects linked with GM maize consumption, which were sex- and often dose-dependent. Effects were mostly associated with the kidney and liver, the dietary detoxifying organs, although different between the 3 GMOs. Other effects were also noticed in the heart, adrenal glands, spleen and hematopoietic system. We conclude that these data highlight signs of hepatorenal toxicity, possibly due to the new pesticides specific to each GM corn.
This is not the only group of researchers to demonstrate an association between GMO consumption and adverse health outcomes. Despite the industries resistance to providing GMO varieties to outside researchers for independent studies, there are still dozens of studies available to the public for review. I’ll synthesize the findings of several of these studies below in considering the possible mechanisms by which agricultural GMOs may cause problems. In general, the health effects of agricultural GMOs are mediated through at least three routes; 1. Directly though ingestion, 2. Indirectly through GMO associated pesticide exposure and ingestion, and 3. Indirectly through environmental and ecosystem effects.
Effects of GMO ingestion:
Ingesting GMOs can affect both the microbiome and human cells. The microbiome is the microorganism population which lives on and in the human body. Most of it exists in or on the mouth, nose, stomach, intestines, and skin. The gut microbiome has received considerable attention due to its apparently profound effect on the immune system, not to mention its effect on food digestion. The gut microbiome is involved in determining the risk of autoimmune diseases, allergic diseases, cardiovascular disease, and some infectious diseases like osteomyelitis. The microbiome can get out of balance (called dysbiosis) and produce severe diseases such as Clostridium difficile overgrowth and more mild disorders like small bowel bacterial overgrowth and irritable bowel syndrome. The bottom line is that a balanced microbiome is critical for health and we are just now beginning to appreciate how serious the consequences of dysbiosis may be.