Pigs, GMOs & Bullshit
So, again, the Internet contends with another negative take on GMOs. Like Seralini’s rat-cancer study from last year, this one involves pigs fed GM and non-GM feed over 22.7 weeks. I don’t have time enough to go through the study, so I’ll briefly summarize the findings of Mark Lynas’ take on the study, as well as another from Weed Control Freaks to show you the pseudoscience indicators:
1st Warning Sign: The results were published in a journal not indexed by PubMed with a low-impact factor; meaning scientists don’t take it seriously.
2nd Warning Sign: The study was funded by The Organic Federation of Australia; i.e., they’re potentially biased. Lynas articulates the position well. Imagine if Monsanto sponsored a study that showed GMOs are safe. The Antis would lose their minds and completely discard.
3rd Warning Sign: The study’s protagonist has a history of anti-GMO activism, and is a cohort of Gille Seralini who himself has a history of anti-GMO activism.
4th Warning Sign: They claim they have no commercial interests, despite many involved with the study standing to gain from increased organic sales if GMOs were shown to be unsafe.
5th Warning Sign: Funding came from Verity Farms (natural product outfit) and The Institute of Health and Environmental Research, which seems to be, according to Lynas, entirely dedicated to anti-GMO activism. Their funding sources are not disclosed, but they solicit donations. Jeffrey Smith and Arpad Putzai are both listed as acknowledgments; the former has no relevant science experience and the latter’s GM potato study that supposedly showed harm is not accepted by the scientific community for methodological errors.
6th Warning Sign: The study showed pictures of severely inflamed pigs stomachs from the GM-fed group against non or mild inflammation from the non-GM fed pigs. Very similar to what Seralini did in his rat study last year. Showing big, fat disgusting tumors from the GM-fed mice, but neglect to show pictures of the control rats who also had tumors.
But, the above are just indicators. In and of themselves, they don’t mean much, but together, they mean a bit; but in science, the data speaks first so let’s get to it. Allow me to summarize some of their findings when he delved into the data himself.
15% of non-GM fed pigs had heart abnormalities, compared to 6% of GM-fed pigs. Liver problems were twice as prevalent in non-GM pigs as GM-fed pigs. (No mention anywhere of these mildly positive findings.) In the four categories of stomach inflammation that was, apparently, the subject of the study: None, Mild, Moderate, Severe. In all but the severe section, the GM-fed pigs were better off than their conventionally fed brethren. There is no dose-dependent mechanism, so the likelihood that there is a correlation between GM-fed pigs and inflammation is next to none. I happen to agree with Lynas’ conclusion:
“My judgement is that, as with Seralini, this study subjects animals to inhumanely poor conditions resulting in health impacts which can then be data-mined to present ‘evidence’ against GMO feeds. Most damning of all, close to 60% of both sets of pigs were suffering from pneumonia at the time of slaughter – another classic indicator of bad husbandry. Had they not been slaughtered, all these pigs might well have died quickly anyway. No conclusions can be drawn from this study, except for one – that there should be tighter controls on experiments performed on animals by anti-biotech campaigners, for the sake of animal welfare.“
Another point by Andrew Kniss over at Weed Control Freaks shows that their P-values were sneakily derived. From the four groups of inflammation, they separated them and ran separate statistical tests so that their P-values could limbo underneath the P < 0.05 mark to be confident in. That is, they went fishing for the right values to validate their hypothesis, which was chosen after the experiment run–stomach inflammation–, a big science no-no; the hypothesis cames up front. When all the results were properly subjected to statistical analysis by Kniss, the P-values came out to be, 0.2142 if running a t-test analysis, or 0.2081 when running a wilcox test. So, that is roughly a 20% chance that the results are consistent with chance, 1/5 is a poor marker for a causal effect. When the males and females were separated and analyzed again, the results were even more stark:
Male t-test = 0.5667 - Male wilcox test = 0.5669 - Female t-test = 0.2564 - Female wilcox test = 0.2408
Andrew Kniss concludes appropriately:
“If I were to have analyzed these data, using the statistical techniques that I was taught were appropriate for the type of data, I would have concluded there was no statistical difference in stomach inflammation between the pigs fed the two different diets. To analyze these data the way the authors did makes it seem like they’re trying to find a difference, where none really exist.“
As Prof David Spiegelhalter wrote to Lynas, so many statistical tests that one was bound to come up positive. Twenty in total were run, and only one, that they had to fish for, showed a result they wanted; which, if we go by the much wanted P < 0.05 that most experiments strive for, lines up perfectly here. Every twenty tests, you would expect one to be random: the severe stomach inflammation that will be paraded around the Internet as “proof” that GMOs are bad for you, ignoring all evidence to the contrary. But, again, it’s not about the science; I doubt they much care about how debunked, criticized, and wrong they are, they only need to create media attention with a facade of science, which Reuters has already bought hook, line, and sinker.
Cami Ryan has another post summarizing rebuttals from around the web of this nonsense study; David Tribe, aka GMO Pundit, also has a detailed breakdown on his site, and I encourage you to read both Mark Lynas’ review (which has been updated now) and Andrew Kniss’ statistical analysis in full.
UPDATE: I mistakenly put the length of the study at two years. David Tribe has since corrected me, it was 22.7 weeks.