Science commentators involved in the genetically modified food debate have weighed in on a new study that says pigs fed genetically modified grains suffered a higher rate of severe stomach inflammation and developed heavier uteri.
Some experts have said the study shows evidence of a problem that warrants further study, while others have dismissed it as alarmist “junk science.” While stoking old flames, the study also highlights difficulties researchers face when patent-holders deny access to genetically modified (GM) seeds for studying.
The study, conducted by Australian and U.S. researchers and published Tuesday in the Journal of Organic Systems, followed 168 pigs from weaning age to slaughter weight over the course of nearly 23 weeks. Half of those pigs (84) ate a diet based on GM corn and soy, while the other half ate as close as possible to the same diet based on conventionally grown, non-GM corn and soy.
The researchers found few statistically significant differences between the two groups after comparing them based on nearly 20 different parameters, including weight gain, stomach ulcers and kidney abnormalities. The GM-fed pigs did, however, show significantly higher rates of “severe” stomach inflammation, as well as an average of 25 percent heavier uteri in relation to body weight.
Stomach inflammation was graded on a scale between nil, mild, moderate and severe during blind autopsies, meaning the reporters did not know if they were examining the stomach of a GM or non-GM pig. A table of four photographs embedded in the study’s paper shows an example of each of the four degrees of inflammation, which ranged from a fleshy grey (nil) to a combination of pink and bile-yellow (severe).
Here’s the number the study’s authors highlight as most concerning: 23 GM pigs had severely inflamed stomachs, while only 9 non-GM did. That much of a difference is a red flag deserving of further study, said Michael Hansen, Ph.D., senior scientist for Consumers Union.
Critics were not as certain. Notable climate change author and GMO critic-turned-supporter Mark Lynas pointed out that 60 of non-GM pigs had mild or moderate inflammation compared with 41 GM pigs, and only 4 non-GM pig stomachs were graded “nil,” while the GM pigs tallied up 8.
Of course, fewer GM pigs can have mild or moderate stomach inflammation if a larger percentage already rate as severe, Hansen said to Food Safety News.
Study highlights GMO research hurdle
Another point of contention lies in the potential variance in nutritional composition between the GM and non-GM grain fed to the pigs in the study. Because of patent-holder restrictions, the researchers were required to buy each type of feed from retail distributors, as opposed to growing the feed in a controlled environment.
According to the study’s authors, the GM corn and soy used in the study were considered compositionally and substantially equivalent to the non-GM varieties by government agencies. But the lack of a controlled feed-growing environment potentially calls the results into question, according to Kent Bradford, Ph.D., director of the Seed Biotechnology Center at the University of California, Davis.
“These are different products,” Bradford told Food Safety News. “For example, soy beans can have a wide range of phytoestrogens. The amount varies widely by production.”
But the study’s researchers had little choice but to work with retail GM grains due to one nearly insurmountable research hurdle: grower’s contracts.
Anyone who buys GM seeds is required to sign a technology stewardship agreement that says, in part, that they cannot perform research on the seed. Without express permission from the biotech patent-holder, scientists and farmers risk facing lawsuits for conducting any studies.
“Any study you want to do with these engineered crops, you need to get the company’s permission,” Hansen said. “Could you imagine if tobacco research was only done when the tobacco companies had the final say?”
In July 2009, a group of 26 public sector scientists wrote to the U.S. Environmental Protection Agency to complain about the restrictions imposed on them by the patent holders of GM seeds. In part, they said critical questions regarding GM foods could not be answered without more research freedom, which has still not been established.
“A fishing trip”
On his Science Denialism blog, Mark Hoofnagle, Ph.D., referred to the study as a “fishing trip,” as it did not set out to answer a hypothesis but instead measured a range of parameters in hope that any differences between the groups would appear. The study should have been treated as preliminary research before engaging in hypothesis-driven testing, he said.
“So far, one can only conclude that it’s just as likely that this result occurred by chance as it is to be an actual effect of feeding the pigs GM corn and soy,” Hoofnagle wrote.
But such feeding studies are published “all the time,” Hansen said.
“When you look at a bunch of things and a lot turns out not to be statistically significant but some are, you look at those further,” he added. “You try to explain the significance.”
Hoofnagle also contested the clinical — if not the statistical — significance of the 25 percent increase of GM-fed pig uterus weights over non-GM. The non-GM group had a mean uterus weight of 0.10 percent of total body weight, while the GM group had 0.12 percent. Those percentages ranged from between 0.04 to 0.31 for the non-GM to between 0.036 and 0.244 for the GM.
Growing conditions questioned
Institutions and scientists who came out in support of the study praised its relatively large sample size of 164 pigs, as well as its duration and farming conditions intended to match those seen in commercial pig-farming operations.
Lynas, however, said the study’s data raised questions concerning the low quality of care the pigs endured. Roughly 60 percent of both pig groups had stomach erosions at slaughter, and nearly 60 percent from each group suffered pneumonia, which Lynas called “a classic indicator of bad husbandry.”
The animals were indeed raised in a commercial environment and the data were similar to what is expected in such a setting, said Howard Vlieger, co-author of the study and owner of Verity Farms in Maurice, Iowa, where the study was conducted.
Once they left the nursery, the pigs were raised in “Cargill-style finishing units,” which include both a straw-bedded enclosure and a fenced outdoor area where the pigs eat and drink.
Vlieger told Food Safety News that while the study could not include any anecdotal behavioral observations of the pigs, the researchers did notice a marked difference in temperament between the two groups. When recording the pigs’ weights each week, researchers say that the non-GM pigs were easy-going and generally cooperative, while the GM pigs were noticeably more irritable.
“For whatever reason, as soon as you brought them into confined quarters, they were fighting and biting each other,” Vlieger said. “Every time we did a weighing, the same scenario presented itself.”
GM contracts still pose research problems
Vlieger also lamented the challenges presented by GM patents. The research team chose not to even attempt obtaining GM seeds because of the long-established refusal by biotech companies.
Hansen reiterated that the study’s findings merited further research into the influence GM grains may have on stomach inflammation and uterine weight. But for that to happen, he said, restrictions on how GM seeds can be studied need to be loosened.
“That’s the way good science works,” Hansen said. “If the studies show the engineered crops are fine, fine. But let the scientists study them the way they want.”
For Bradford, the main concern with the study stems from those input limitations. Until GM and non-GM grains can be grown under the same conditions and then administered in a feed test, the results come into automatic question.
“It looks like they did a reasonably careful study,” Bradford said. “It’s just that if you don’t control the food going in, it’s hard to substantiate what comes out. It will be interesting to see what other studies come after this, but right now it’s hard to get too excited.”