Genetically modified corn and cancer – what does the evidence really say

This study has shown that old Harlan Sprague-Dawley rats get cancers and other diseases. This has been shown before.

What this study does not show is that exposing these rats to GM corn and/or Roundup makes any difference to the frequency of cancers or other diseases. It can’t because no statistical tests have been applied, and perhaps most worryingly, the authors do not comprehensively report on why rats in the control group died.

To answer the captioned question – the Seralini study show that an extremely cancer prone strain of rat gets cancer during its lifespan. Ashley Ng has published a devastating critique of the Seralini study. Dr. Ng is a Post Doctoral Fellow and Haematologist at Walter and Eliza Hall Institute of Medical Research. Snippets:

Rat selection

The study focuses on cancers in rats. For this they use the Harlan Sprague-Dawley strain of rat, which is known to be predisposed to getting cancer. Lots of them. Over 70% of males and 87% of females from this strain reportedly get cancer during their lifetime, whether they have been fed GM corn or not. So it shouldn’t be a surprise that so many of Seralini’s rats were found with cancer.

To make sense of this study you have to ask the simple question: “does feeding rats GM corn and/or Roundup increase the frequency of cancers compared with rats that have been given non-GM food?”

To do this, the authors of the study split up 200 rats into ten groups. One “control” group (ten male and ten female) were fed non-GM corn and had access to plain water. The researchers monitored for the development of cancer over a period of two years.

Nine other groups of twenty rats (ten male and ten female) were also monitored, but this time, these groups were given food containing 11%, 22% or 33% of NK603 GM corn, 11%, 22% or 33% of NK603 GM corn with Roundup spiked in their drinking water, or just Roundup spiked in their drinking water at different concentrations.

The male and female rats in the control group lived for just under two years. Other studies identified that these rats die from cancer or kidney failure around this time. But the authors don’t mention this. They simply write:

“ After mean survival time had elapsed, any deaths that occurred were considered to be largely due to aging.”

They have effectively chosen not look at – and therefore don’t have to report on – why rats in the control group died. This assumption alone is sufficient grounds for rejecting this paper from publication.

Treatment group vs the control

In the study, Figure 1 (view here) shows Kaplan Meier plots the number of rat deaths by “control group” and other “treatment groups”.

What do these mean? Well, not much because the authors failed to use a statistical test to tell if there was a difference between the control groups and treatment groups.

This is important, as all their claims relate to the incidence of cancers (and other “diseases”) in the “treatment group” compared to the “control group”. These comparisons can only be made if a statistical test shows that what you observe is not happening by chance.

The Harlan Sprague-Dawley strain of rat is predisposed to getting cancer. jepoirrier

Overstating the evidence

Still on Figure 1, we see that several “treatment groups” of male rats receiving GM NK603 corn (the 22% group and 33% group) actually had fewer cancers than the male control group at their arbitrarily determined point of assessment.

Similarly, a treatment group of male rats receiving 33% GM corn and Roundup had no difference to the control group, and two treatment groups receiving Roundup (A and C) had the same or less incidence of cancer compared with the control group.

By their perverted logic, they could equally claim that for male rats:

a) high percentages of GM corn (22% and 33%) was “protective” against getting cancer compared to group of control male rats

b) having 33% of GM corn with Roundup showed no difference to the control group and therefore wasn’t harmful to male rats, and

c) using 0.5% Roundup in the drinking water was protective against cancer in male rats compared to the the male control group.

But you can’t. You can no more make these statements than the claims about the increased incidence of cancers in the female rats in the various treatment groups. No statements can be made because no statistical test has been applied.

The full picture

One sentence that should set alarm bells ringing is the claim that “All data cannot be shown in one report.”

The retort to that statement is, “Oh yes it can. Please show it to me”. If you are reporting data, you need to show all the data.

Do read Dr. Ng in full. Then sign the petition to force Seralini to release their data.