In addition to the apparent lack of scientific follow-up on the long-term rat-feeding study of Monsanto’s NK603 genetically engineered (GE) corn carried out by Séralini et al., I found various comments among the many letters to the editor of the journal that retracted the paper disconcerting.

These letters, most written by researchers who utilize plant GE technology themselves, often contained statements like “As scientists, it is important for us to help make sure that debate, legislation and policy decisions are based on well-grounded scientific evidence.” I wholeheartedly agree and add that “well-grounded scientific evidence” should include all available well-grounded science; “cherry-picking” scientific evidence does not serve the best interests of public debate, legislation or policy related to GE–or any other other–technology. As Albert Einstein put it: “The right to search for the truth [i.e. do science] implies also a duty; one must not conceal any part of what one has recognized to be the truth.”

Nevertheless, some letter-writers failed to mention among their comments some well-grounded scientific evidence relevant to this important public debate.

For example, Wagner et al. mention that the “herbicide glyphosate…affects an enzyme present in plants, but not animals….” But what these authors failed to mention is the long known fact that glyphosate can also affect biochemical pathways in microorganisms, including beneficial microorganisms which inhabit animals–including humans–and the environment. The importance of the human “microbiome” (the collective genomes of all the microorganisms that inhabit human gastrointestinal tracts, e.g.) has been a focus of many scientific studies over the last couple of decades and, more recently, adverse effects of glyphosate on microorganisms found in agricultural soils and also in the gastrointestinal tracts of animals have been documented in peer-reviewed scientific papers.

And then there was Sanders et al. who concluded the body of their letter-to-the-editor with a paragraph that begins “[Séralini et al.] ignore the fact that genetic modification is a technology.” They go on to imply that the effects of using this technology are associated only with the function of the inserted foreign gene and not with the process of transformation itself. Their comments ignore the fact that, as currently practiced, the GE transformation process itself can cause unintended, unexpected changes, including mutations (rates of 27-63% have been published in the scientific literature), in the recipient organism. (In fact, the rates of “insertional” mutations associated with one of the two primary methods for inserting genes into plants are so high that plant scientists have utilized that method to mutational “tag” and thereby isolate many plant genes.) The possibility that unexpected, unintended changes could occur in GE crops is a main reason for conducting long-term rat-feeding studies like the one carried out by Séralini et al.

I do agree with Sanders et al. that “Even if a [specific GE] trait were somehow toxic this doesn’t translate to GM technology as a whole.” However, because unintended, unexpected effects can occur as a result of any use of current GE transformation technologies, each and every product of this technology should undergo mandatory regulatory scrutiny prior to commercialization.

Monsanto’s NK603 GE corn event itself, the subject of Séralini’s controversial paper, serves as a good example of the kinds of unexpected things that can happen as a result of the GE transformation process (with the apparent exception of insertional mutation). (Monsanto sequenced the corn DNA around the NK603 insertion site and so it should know whether its foreign DNA landed in a corn gene or not, but I have not been able to find any reference as to its determination with regard to this transformation phenomenon.)

At the DNA level in NK603 GE corn there was an unintended deletion of corn DNA and an unintended insertion of choloroplast-like DNA at the site where the foreign Monsanto-designed DNA was inserted; there was also an unintended duplication of part of one of the two Monsanto-engineered genes.

At the RNA level Monsanto scientists “demonstrated that mRNA transcription was detected to initiate in either of the two [foreign gene] promoters of the NK603 insert and proceed through the [signal intended to stop the expression of the foreign gene(s)] and continue into the corn genomic DNA.” Although in Monsanto’s Safety Assessment of NK603 GE corn this result was described as “not unexpected,” I nevertheless assume (hope) it was unintended.

At the protein level, one of two additional changes to the DNA sequence in one of the two inserted genes in NK603 GE corn converted a “leucine codon to a proline codon at position 314” in the protein encoded by that foreign gene. So, the protein expressed by that mutated foreign gene in NK603 GE corn is slightly different than the one Monsanto had intended to express in this GE corn product.

To reiterate…a main reason for conducting animal feeding studies with GE crops is because unexpected, unintended changes like these that have occurred in the DNA, RNA and protein of commercialized NK603 GE corn, could possibly result in adverse changes in a GE crop. The process of genetic engineering (i.e. transformation) itself can, in fact, dictate effects in recipient plants despite the statement by Sanders et al. that the “process of transformation does not.”

And because glyphosate-tolerant GE crops like NK603 corn are now grown on hundreds of millions of acres of agricultural land in the U.S. today, resulting in vastly more glyphosate coming in contact with soil microorganisms and the food we humans and other animals eat, it’s time to re-examine glyphosate’s “long history of safe use” in the environment at much lower levels in light of these quantitative increases. After all, the dose makes the poison.

And absence of evidence is not evidence of absence. More well-grounded scientific evidence is needed to inform the public debate about GE technology. That and less cherry-picking of what evidence is already available.