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What does the research conclude about the bioaccumulation of bt toxin resulting from humans consuming GMOs? And did the producers of GMOs produce the evidence of its safety to the FDA before putting these products on the market?

Submitted by: Doug Ittner_2


Expert response from Kevin Folta

Professor and Chairman, Horticultural Sciences Department, University of Florida

Tuesday, 13/08/2013 20:29

What do you think would happen if a 200-pound human being was force-fed, with a tube down the throat into the stomach, pure bacterial spores equivalent to half a roll of nickels, and then tested for effects 24 hours later? My guess is that you’d see a screaming immune response, massive response from gut flora and probably some effects on physiology that would be reflected in the blood. Agreed?


If you agree, then the results of this hypothetical “experiment” are the same as those performed on mice in the Mezzomo study.


In short, the work by Mezzomo et al. (J. Hematology and Thromboembolic Disease) takes Bt spore crystals (dried-down Bacillis thruengenesis bacteria) containing the different Bt protein (or Cry proteins) and delivers them by oral gavage into the stomachs of mice. The authors show that mice exhibit minor changes in the blood 24, 72 and 196 hours after the treatment. The authors claim that these findings indicate that “further studies are needed to clarify the mechanism involved in hemotoxicity…to establish risk in non-target organisms.”


Upon analysis, I completely disagree with the authors.  The study does not show this at all.


Here are a few of the study’s significant limitations.   


  1. No experimental control was used (well, just water). There were no bacterial Cry minus strains tested, so it is impossible to know if the effects come from the bacteria or the cry proteins. The cry protein is what is used in transgenic (GM) plants.
  2. The bacterial strains used with the Cry gene (a Bt protein) were originally characterized by Santos et al. (BioControls, 2009) to test for larvacidal activity against various cotton pests. Larvae were fed the spore crystals, just as they would when about 5060 percent of organic growers apply Bt to plants. They do not test transgenic plant materials yet make clear statements implying that these results are relevant to transgenic contexts. This statement completely oversteps the data. 
  3. The levels of Bt were at least one million times what humans consume when eating transgenic corn.
  4. The study has a problem that is seen in most GMO studies. There is no real dose-response relationship. In other words, if something has an effect, you see it more when more when a greater amount of the causal agent is applied. Here, Table 1 shows a number of instances where lower doses produce significantly lower effects.  This is always a red flag to critical scientific reviewers and usually means the sample size is too small and the differences reflect natural variation.




When you force-feed massive numbers of bacterial spores to mice, they will have responses that may be detected in the blood.  The responses can be detected but likely are not even biologically relevant.  Even seven days after being infused with bacteria, the mice show only small changesjust a few percent, at best.  So when the websites say, “GMOs are linked to leukemia and anemia,” the real answer is that mice fed quite a bit of Bt-containing bacterial spores (like the ones used in organic production) have tiny changes in certain blood biomarkers.


Other notes:


  1. This was the inaugural issue of JHTD. I could not access its current list of contents (it gave a jpeg of the journal's cover), but it does claim to be “one of the best open access journals of scholarly publishing.” Quite a statement for a journal that launched in 2013 and has no impact rating. In the SCImago Journal Ranking system, among 89 journals in Hematology, JHTD ranks…well—it did not even make the list, and the 89th-place journal has not published a paper in the last three years.
  2. The Omics publishing group is widely criticized as a “predatory publisher.” This means that they get paid every time something is published and actively seek articles to publish. They are known in scholarly circles for not publishing high-quality work, and few, if any, of their journals are indexed on PubMed, which means they have not met PubMed's quality metrics.
  3. Biofortified author Dr. Anastasia Bodnar notes that the work was originally published in the respected journal Food Chemistry and Toxicology (November 9, 2012) but was “withdrawn at the request of the author(s) and/or editor.”  As Elsevier's withdrawal guidelines state, an article may be withdrawn if it contains errors or if it was submitted twice. If the paper had errors or was submitted twice, those problems could be remedied for resubmission. The other reason stated in the policy is when “the articles may represent infringements of professional ethical codes, such as multiple submission, bogus claims of authorship, plagiarism, fraudulent use of data or the like.”


In conclusion:


The article is consistent with the low-quality, low-impact, no-control, no-dose-response, limited-biological-relevance, poorly designed studies that are held in sterling regard by the anti-GMO community. It is again a testament to how bad research and claimed effects will forever be integrated into the fabric of a movement and will be used to scare the credulous and even affect public policy. 


The bottom line is that the Bt protein is just thata protein. It is digested by humans, just like any other protein.  There is no evidence of bioaccumulation. The compound has been well studied for decades and has been a great benefit to organic growers, as well as in a transgenic context.