October 26, 2004
Study: GMOs safe for environment, human use
CARBONDALE, Ill. -- Research conducted at Southern Illinois University Carbondale supports the growing sentiment in the scientific community that genetically modified organisms - or GMOs as they're commonly called - are safe for human consumption and for the environment.
No traces of a "foreign" gene wound up in the flesh or blood of 56 piglets fed genetically modified corn, SIUC researchers found.
While they did detect bits of the corn's transgene in the stomach contents of 50 of the piglets, they found it in only one of the samples screened from the small intestine, suggesting further that the additional gene generally does not survive the digestive process.
This new study reinforced findings from earlier work with samples of contents from the small intestine and feces of larger pigs in which SIUC researchers found no remnants of the transgene at all.
"It seems like it degrades rapidly," said swine expert Gary A. Apgar of the College of Agricultural Sciences.
"Most, if not all, of the transgenic material is gone by the time the digesta is excreted. We found no evidence that it is absorbed (into the animal), and the risk of its coming out in the environment in the form of waste is non-existent because we failed to find the gene in either the colon or the feces. While nothing can ever be guaranteed 100 percent safe, I think there's no need for concern (about eating meat from animals fed transgenic diets)."
Apgar believes the weight of scientific evidence supports the idea that GMOs are safe.
"If we look at the amount of transgenic crops that have been created and the lack to date of negative effects in the human and animal worlds, I think that's confirming what we have seen here (in this study)," he said.
The SIUC study, conducted with the help of Janet M. Beagle, now a doctoral student at Purdue University, is part of an overall look at GMOs as a component of swine diets. The Council for Food and Agricultural Research and the Illinois Corn Marketing Board paid for the research.
American farmers generally like GMOs, which provide improved yields, health, pest resistance and the like. Federal statistics show that in 2002, 34 percent of the country's corn crop consisted of GMOs. Worldwide, more than 168 million acres are planted in biotech crops -- a 4,000 percent increase over the last eight years, according to Truth about Trade & Technology, an Iowa-based biotechnology advocacy group.
Much of the corn grown in this country -- more than 60 percent, according to National Corn Growers Association statistics released last year -- becomes animal feed.
"The number of crops that are genetically modified grown throughout the world are increasing exponentially, but there's very limited data on what happens 'downstream,'" Apgar said.
"There are a few rat studies, three swine studies, a couple of studies on feedlot steers, but none of them are as comprehensive as our work. We're taking a total systems approach, looking at every aspect of a single animal -- meat, fecal material, blood, digesta -- at different ages."
Using a transgenic corn developed at SIUC but not available commercially, Apgar and his graduate students first showed that pigs digested both regular and modified corn in pretty much the same way.
When they looked for evidence of the gene in the pigs' stomach contents and feces, they found nothing.
"That didn't tell us where it went -- just that it was no longer in the digesta," Apgar said.
"So in this study, we looked at most of the places that gene could be -- the GI (gastrointestinal) tract, the blood from the major vein out of the GI tract into the liver, the liver itself and muscle tissue."
They used weanling pigs this time around instead of the 90-pound grower pigs from the earlier study because the little ones are more efficient at turning a pound of feed into a pound of gain, hence increasing the potential for the transgene to be absorbed.
"That meant the potential for the gene to get through that limited digestive capacity and be absorbed (into the animal) intact might be greater, too," Apgar said.
They also ran their tests twice, once with the analytical tool they'd used in previous work and once with a more sophisticated version of it.
"(The upgraded version) has improved our detection limit while producing an actual numeric value for what we're seeing," Apgar said.
Using the older tool, they found bits of transgene in 40 of the 56 stomach samples and in one of the samples from the small intestine. While the more sensitive equipment turned up evidence of the gene in 50 stomach samples, screening of the small intestine samples still yielded only one positive result. And even the more sensitive equipment could not detect traces of the gene anywhere else.
"Overall, the findings are much more positive than negative," Apgar said.
"Is the fact that we found a single trace of transgenic DNA in the small intestine significant? Not to me, but it might be to you if you're already concerned about food safety. Until we can better characterize the degradation of dietary DNA, we might be a little cautious, but at this point I wouldn't say, 'Throw the brakes on!'"
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