Lots has been made of a report that GMO feed causes stomach
inflammation in pigs.
As usual, popular accounts of the science don’t tell the
whole story. If you read the study, and we did, you’ll find it doesn’t say
exactly what they’re saying it says.
The study, published in the Journal of Organic Systems, is
entitled “A long-term toxicology study on pigs fed a combined genetically
modified (GM) soy and GM maize diet.” Researcher authors are American and
Australian, and include organic farming advocates, although they assert that they have no conflicts. The journal, which is Australian, is supported in part by the Organic Federation of Australia, the Australian government, and a New Zealand sustainable agriculture organization, CSAFE.
They separated 168 pigs into two equal groups, feeding some
organic corn and soy, and others corn and soy that had been genetically
modified for insect and/or herbicide resistance. (A few young pigs in both
groups died during the 23-week trial, at rates that the authors say are
standard for commercial hog production.)
The study admits that the GM-fed pigs were fed somewhat moldy
feed, while the non-GM pigs received feed with less significant levels of mold.
“Mycotoxin analyses (Midwest Laboratories Inc, Omaha, Nebraska, US) showed 2.08
ppb total aflatoxins and 3.0 ppm total fumonisins in a pooled sample of the GM
feed and no aflatoxins and 1.2 ppm total fumonisins in a pooled sample of the
non-GM feed.”
But the authors insist that this had no impact on their
results: “The concentration of mycotoxins in the feed was insignificant.”
In virtually every test the researchers recount, there was no
statistical difference between the two groups of pigs. They were inspected and
blood was taken when they were alive, and they were autopsied once they were
slaughtered.
“There were no differences between pigs fed the GM and non-GM
diets for feed intake, weight gain, mortality, and routine blood biochemistry measurements,”
they wrote.
The only significant difference was stomach inflammation,
and even that is not nearly as clear as you’d expect, given the way the popular
press has told the story.
Most of the pigs in both groups had some level of stomach
inflammation, although it was not equally distributed. And in fact, 11 percent
of GM-fed pigs had no stomach inflammation whatsoever, while only 5 percent of
non-GM-fed pigs had no stomach inflammation at all.
Of 73 non-GM pigs, 69 had some level of stomach inflation.
Of 72 GM-fed pigs, 64 had some level of stomach inflammation. The difference:
in the pigs with severe inflammation of the stomachs, more tended to be GM-fed.
If you’re appalled at the presence of any stomach
inflammation in pigs, know that it’s a common occurrence due to feed preparation:
“The pig industry uses finely-ground feed to maximise feed efficiency which can
increase inflammation and ulceration of the stomach,” the authors note.
The researchers wisely say—as researchers commonly do—that their
results demand more study. What are the odds that the results would be different if you did the same study again?
But just to be clear, while their results show statistically
that severe inflammation of the stomach was more common in the GM-fed pigs, it
is also true that inflammation as a whole was more common in the non-GM pigs.
And it would be technically accurate, though also misleading,
to write a headline that said: “Stomach inflammation in pigs higher when
fed organic diet.”
© Jan TenBruggencate 2013
