Do GMOs adversely impact humans? Thousands of studies have been performed over the past 20 years attempting to answer in part that question. The consensus, of course is ‘no,’ and it’s supported by massive numbers of independent reviews by, among others, the National Academies of Science in the US and the European Commission.
Nonetheless, researchers, sometimes for what appear to be ideological reasons, review selected previous studies and offer their reinterpretations, raising doubts about the consensus. That appears to be the case recently.
In January 2022, a study by Chen Shen and 2 co-authors published in Environmental Sciences Europe addressed the adverse effects in humans and animals from the intake of genetically modified organisms (GMOs) or products derived from them was published. The study emphasized GM soybeans, corn and rice. Their claimed objective:
A systematic review of animal and human studies was conducted on genetically modified (GM) food consumption to assess its safety in terms of adverse effects/events to inform public concerns and future research.
Their conclusion directly contradicted the summary interpretations of more than 2500 existing studies:
Serious adverse events of GM consumption include mortality, tumour or cancer, significant low fertility, decreased learning and reaction abilities, and some organ abnormalities.
This analysis examines the team’s methodology. The conclusion reached is that it is sloppy and substandard at best and ideologically-motivated at worst.
How were the studies selected?
The authors screened seven databases and 84 other sources for feeding trials with GMOs for the period January 1, 1983 July 11, 2020 and found a total of 9668 hits. After more detailed, elimination of duplicates, excluding non-targeted experimental design etc, they finally identified 204 studies (203 on animals, one on humans) in which adverse effects were observed. The publication does not specify the adverse effects or the toxicological effects in more detail. Only tables 2-5 list adverse effects such as mortality, life span or survival rate, cancer rates, reproductive rate, organ changes.
For the 204 studies, 179 literature references are cited (Refs. 19 – 197). The discrepancy between the number of studies and literature citations can partly be explained by the fact that some literature citations are listed several times for feeding trials with observed adverse effects (e.g. Refs. 26, 32, 35, 69, 74) although they were found in one and the same study.
From the outset, the paper makes some questionable claims. The authorsstate that the European Food Safety Authority (EFSA) is one of the leading institutions that identifies feeding studies with adverse effects and publishes them in its ESFA journal. This is certainly not correct. EFSA does not carry out any feeding studies itself but analyzes and evaluates data submitted by the applicant about the GM plant or product and the published studies on this in the context of authorization procedures on a scientific basis.
It is incomprehensible in the publication that Ref. 35 is only given for GM plants, although EFSA has published more than 20 opinions for the investigation period (2017-2020). The results of the scientific opinions are always similar to that of Ref. 35: The product as described in the application is as safe as is conventional counterpart.
The EFSA opinions published here also include the GM maize NK 603 x MON 810; NK 603, MON 810, MON 863, MON 863 x MON 810 x NK 603 and GM soybean GTS 40-3-2, which are particularly mentioned to serious adverse effects. Here the publication EFSA´s scientific opinions are widely misinterpreted.
Further, the publication states that EFSA has observed or found adverse effects upon the intake of 12 food enzymes from GM microorganisms (Refs.76 – 87). However, the publication does not mention which effects are involved, leaving it up to the reader to find out. It is incomprehensible why these 12 opinions of EFSA or better of the CEF/CEP Panel, respectively were selected, although 39 other opinions on food enzymes from GM microorganisms were published in during the same period but are not mentioned.
Likewise, it is not clear why certain persons from the scientific panel are specifically mentioned, as the opinions are supported by all members of the panel. If one analyzes all the opinions of the panel on food enzymes, an allergic reaction of the food enzyme can be identified as a possible adverse effect. However, an allergic reaction cannot be ruled out for any enzyme, regardless of whether it comes from a conventional or GM organism. Thus, references 76 – 87 should not be listed as evidence of adverse effects of products derived from GMOs or GMMOs.
Primarily, the publication conveys that every one of the 179 references listed, adverse effects from the intake of products from GMOs on the health of humans and animals are actually found or that there are serious differences to the comparable conventional counterpart. That’s not true; not even close.
Not all of the 179 references, especially those in Chinese (83) and Japanese (2), were analyzed here, but many were. Here are nine selected at random (Refs. 19, 20, 24, 30, 35, 50, 52, 64, 95). ot one describes any particular abnormalities with regard to toxic effects or differences to the corresponding counterpart.
Analyzing the studies claiming to document adverse effects
Here are randomly selected references, along with relevant actual conclusions from the papers:
Ref. 19, ► Al-Harbi A. et al. (2019): “No adverse clinical or behavioural effects, or biomarkers of adverse health, were observed in rats fed GM corn compared to the other corn diets. These findings suggest that MON810 has negligible effects on the small intestine of rats at the cellular level compared with the well-documented toxicity observed in susceptible insects.
Ref. 20, ► Appenzeller L.M. et al. (2009): “These results support the comparative safety and nutritional value of maize grain from genetically modified Optimum® GAT® and conventional, non-transgenic hybrid field corn.”
Ref. 24, ► Buzoianu et al 2012 “Long-term feeding of GM maize to pigs did not adversely affect growth or the selected health indicators investigated”,
Ref .30, ► Chukwudebe A. et al. (2012): “Hence, introduction of AHAS gene into soybeans does not substantially alter its compositional properties, nor adversely affect its nutritional or safety status to mammals.”
Ref. 35, ►EFSA (2018) “In conclusion, soybean MON 87751, as described in this application, is as safe as its conventional counterpart and the tested non-GM soybean reference varieties with respect to potential effects on human and animal health and the environment.”
Ref. 50, ►Lin T.H. et al (2016): “Results of immunotoxicity assays revealed no consistent difference between rats fed for 90 days with GM 823-2210 papaya fruits, as opposed to those fed non-GM TN-2 papaya fruits, suggesting that with regard to immunomodulatory responses, GM 823-2210 papaya fruits maintain substantial equivalence to fruits of their non-GM TN-2 parent.”
► Ref 52, ► Liu Q. et al (2017):” Although differences in some serum chemistry parameters (alanine aminotransferase of female pigs and alkaline phosphatase of male pigs) were observed, they were not considered treatment-related. On the basis of these results, long-term intake of transgenic rice carrying Cry1Ab protein exerts no unintended adverse effects on WZSP offspring.”
Ref. 64, ►Papineni S et al. (2017): “Under the conditions of this study, the genetically modified DAS-444Ø6-6 diets did not cause any treatment-related effects in rats following 90 days of dietary administration as compared with rats fed diets with soybean of isoline control or commercial reference controls and are considered equivalent to the diets prepared from conventional comparators.”
Ref. 68, ► Qian Z.Y. (2018): “ Based on these results and entire weight of evidence evaluation, it is concluded that the histopathological changes previously noted in the 2 female Wistar rats of Tianjin study were not treatment-related and that DAS-44406-6 soybeans are as safe as conventional non-GM soybeans.”
Ref. 95, ► Walsh M.C. et al. (2012): “Conclusions/Significance: Perturbations in peripheral immune response were thought not to be age-specific and were not indicative of Th 2 type allergenic or Th 1 type inflammatory responses. There was no evidence of cry1Ab gene or Bt toxin translocation to organs or blood following long-term feeding.”
Ref. 125, ►Huang Q et al. (2009) not related to gene engineering.
Ref. 151, Song L.S. et al. (2017): This reference could not be checked, the information is probably incorrect. The article is not present in the bibliography list of Song L.S.
Ref. 185, ► Zhi et al. (2011): “Conclusion: There were no signs of toxic and adverse effects for transgenic human alpha-lactalbumin powdered milk on rats.”
The publication does not explain why these references are listed as evidence of adverse effects, when that is obviously inaccurate. In accordance with good scientific practice, one might have expected that in the list of references (Refs. 19 – 197) the studies in which no adverse effects were found are marked. But this is not the case. Thus, the impression remains that the intention is to suggest that negative effects were proven in all of the studies.
Even if not all references could be analyzed in detail, it can be assumed that only 14 of the studies listed in Tables 2 – 5 (Ref. 26, 31, 32, 35, 37, 42, 68, 69, 74, 88, 97, 156, 193, 196) actually observed or demonstrated adverse effects. It is noteworthy that only four studies from China are listed, although almost 50% of the cited studies were performed in China.
Studies dubiously listed as showing ‘adverse effect: death, increased death rate, cancer
A review of few of some of the studies that did make claims of adverse effects, proved problematic:
Ref. 32. Cyran N. et al. (2008) is mentioned under 32a, 32b, 32c; but it is always the same study). The reference should more correctly read: Velimirov A., Binter C., Zentek J. (2008): Biological effects of transgenic maize NK603xMON810 fed in long term reproduction studies in mice. Research Reports of Section IV (Volume 3/2008) of the Federal Ministry for Health, Family and Youth. This is an unreviewed report. The research was funded by the Austrian Federal Ministry of Health, Family and Youth. However, this report was withdrawn by the Ministry due to serious methodological errors in the test procedures and in the statistical evaluation. The research results were considered unconclusive and unusable.
It is surprising that the authors of the publication did not notice the discrepancies when evaluating the report. The report is no longer listed on the ministry’s website, nor is it available on request. The Zentek study certainly cannot serve as scientifically verifiable proof for the adverse effects listed in Tables 3 and 4.
In the context of the Zentek feeding study, it is not understandable that the authors did not mention the multi-generation study by Hu et al. (2020): Three-Generation Reproductive Toxicity of Genetically Modified Maize with Cry1Ab and epsps Genes in Rats. This quite similar study found no ill effects.
Ref. 74 refers to the well-known long-term feeding study by Gilles-Éric Séralini
from 2012, which assessed the impact of GMO corn and glyphosate. It was accompanied by pictures of rats with large tumors—the result not from the corn or glyphosate but of using fast-mutating rats. Scientists and regulatory agencies around the world subsequently evaluated and eviscerated its methodology. The study was retracted the following year. It was later republished in a non peer-reviewed ‘predatory’ journal.
The effects listed in Tables 3 and 4 were mainly taken over from Ref. 74. These data derived from the initially withdrawn study (Ref. 14). The tables give the impression that the data listed are scientifically recognized. This is by no means the case. The overwhelming criticism on the Séralini study is not mentioned anywhere in the publication.
Furthermore, the studies of the GRACE-, GwYST- and GMO 90* projects are not mentioned here, although these studies were carried out as a follow-up to the Séralini tudy. The results from these investigations refute or could not reproduce the results of Séralini . These studies were all published within the study period of this publication. Ref.104, 105 derived from the GRACE project, but they are not mentioned in any way in relation to the retracted study. Although Ref. 104, Ref. 105 indicated no adverse effects, these two publications are listed among those with negative effects due to the consumption of products derived from GMO.
So far, Séralini’s results have still not been verified and it is more than doubtful that the adverse effects listed actually occurred.
►Ref. 69 Tudisco R. et al. (2015): This report must be included in a whole series of studies, to which Ref. 57, Ref. 58 and Ref. 59 can also be counted. Curiously, the other studies from the working group around Tudisco and Infracelli are not mentioned in this publication. The information given in Tab. 4 is correct, but only incomplete. The slaughter weights of lambs fed with colostrum or milk from GM soy meal-fed dams are lower than those from the control group. A dose dependence of the slaughter weights is not detectable. In the body measurements, the lambs differ slightly in terms of height at withers and chest circumference, while there are no differences in the weights of the organs. Due to considerable methodological deficiencies, the study is not suitable for making substantial statements on the development of ram lambs fed with colostrum (Bistmilch) / milk derived from dams fed with GM soy.
Ref. 88 ►Talyn B et al. (2019): The title of this publication “Roundup, but not Roundup-Ready corn, increases mortality of drosophila melanogaster” is misrepresented as well.. Apparently, the GM maize itself has no influence on the lifespan of Drosophila melanogaster, but rather the pesticide used. Therefore, the reduced lifespan is a direct effect of the spraying agent and not a causal effect caused by the genetic modification of the maize.
While neither lifespan nor reproductive behaviors were affected by HT corn, addition of Roundup increased mortality with an LC50 of 7.1 g/L for males and 11.4 g/L for females after 2 days of exposure.
— Ref. 88
It is not discussed why Ref. 88 is listed as a publication demonstrating adverse effects due to genetic engineering of the plant. It is simply listed as a negative effect of genetic engineering.
Almost the same can be stated about Ref. 35, Ref. 68, Ref. 156 and Ref. 193 listed in Table 3, 4 under severe adverse effects as “mortality” or “survival rate”. In the references as well as in the tables, the observed mortality is not related to the test substance. Animals were found dead in the cage during the experiment and the cause of death could not be determined. The accidental death of individual animals is very often observed in such studies. This is not uncommon and certainly not specific to feeding trials with diets containing GMO products.
Further in some studies the premature death is due to the gavage feeding, the handling of the animals or the housing conditions. In Ref. 196, the individual surviving rate of the animals is found to be similar to the control group. Therefore, it can be assumed that the causes leading to the death rates are similar to both diets and unrelated to the genetic modification of soybeans. From a scientific point of view, it is not justified to attribute the adverse effect to genetic modification.
Unfortunately, the publication does not give any explanation or discussion as to why the authors list these feeding trials as studies demonstrating the serious negative effects (increased death rate) of GM feed. Numerous other investigations were carried out around the studies of Ref. 156 and Ref. 193 and in all of them no negative effects or serious differences to the conventional counterpart could be found.
Conclusion
The selected studies. many of which are misrepresented, present a bizarre picture about the safety of GMO crops. Every major scientific body and regulatory agency in the world has reviewed the research on GMO crops, including most of the studies cited here, and definitively declare crop biotechnology and the foods currently available do not present any unique health hazards. GM crops are as safe–and in the case of nutritionally enhanced varieties, such as Golden Rice, healthier–than conventional and organic crops. Here are summary statements from 12 independent global organizations.
Is there any value to this paper? A positive aspect is that it provides a good overview of feeding studies with GMOs and/or products derived from them, especially studies conducted in China.
However, the researchers selectively chose studies to draw a distorted interpretation and misrepresent key data and therefore the publication does not demonstrate scientifically proven negative toxic effects from the consumption of foods grown from genetically engineered seeds. As such this paper is misleading and open to exploitation by advocacy groups less interested in science than in promoting a biotechnology-rejectionist agenda.
Klaus-Dieter Jany, a retired biochemist, was for many years at the Federal Research Center for Nutrition beginning in 1989. He became head of the Molecular Biology Center in 1992. The focus of his work is on the application of genetic engineering in the food sector.
