SEATTLE — Backers of Initiative 522, which would make Washington the first state to require labeling of genetically engineered foods, are careful to couch their arguments in terms of the public's right to know, rather than public health. But the text of the measure — and the subtext of the debate — both raise the specter that eating genetically engineered food could be bad for you.
It's a concern many people share. But sorting through the rhetoric and cherry-picked data is like wandering through the fog without a compass.
"People are positively swimming in information about GM (genetically modified) technologies," the journal Nature noted in a special issue on the topic this spring. "Much of it is wrong — on both sides of the debate. ... (With GM crops, a good gauge of a statement's fallacy is the conviction with which it is delivered.)"
Definitive answers are always hard to come by in science, and those who demand unequivocal proof of safety will never be satisfied. But two decades of research and analysis have converged on a conclusion that even most opponents of the technology accept: There's no evidence that genetically engineered foods on the market today harm the health of people who eat them.
That doesn't rule out the possibility of long-term effects, nor is it a blanket assurance that the approach is risk-free. Even ardent supporters acknowledge genetic engineering has the potential to produce crops laced with toxins or compounds that trigger allergic reactions. But so does conventional breeding.
In fact, traditional techniques have yielded several foods that caused health problems for consumers and farm workers, while there have been no such cases documented from genetic engineering.
Health concerns are only one factor people weigh in staking out their positions on transgenic foods. Environmental and pesticide effects (which will be covered in a future story) matter to many, as do personal values and philosophies about corporate control and transparency in the food supply.
But when it comes to food safety, pro- and anti-GE camps diverge most profoundly on two fundamental questions:
Perhaps the most compelling evidence for the safety of GE crops is that millions of people have been eating them since the mid-1990s without obvious harm.
That's not surprising, said Greg Jaffe, director of biotechnology for the Center for Science in the Public Interest. Like most food, foreign genes inserted in a plant's DNA and the proteins they produce are largely broken down in the gut and digested.
Also, the vast majority of GE foods on the market today contain only one or two added genes, Jaffe pointed out.
A single bacterial gene is inserted in corn, soybeans, cotton and sugar beets to make the plants resistant to the herbicide glyphosate, or Roundup. The gene produces a protein that protects the crop from the herbicide's effects, allowing farmers to spray their fields and kill only the weeds.
The other major class of GE crops is those modified with a different bacterial gene to produce a natural pesticide called Bt (for Bacillus thuringiensis), toxic only to certain insects like corn borers. Most U.S. cotton and corn has been engineered to produce Bt.
Eating corn with a built-in bug-killer sounds scary, but Bt is considered so environmentally benign — and harmless to humans — that it is widely used in organic farming. Most plants produce natural pesticides to discourage insects from eating them, and several crops have been conventionally bred to contain high levels of those chemicals.
About 90 percent of corn, soy beans, cotton and sugar beets grown in the U.S. are genetically engineered, and at least one of those crops shows up in the vast majority of chips, cereals, soft drinks, crackers and other processed foods.
The Achilles' heel of GE safety studies is their brevity. Companies are only required to feed new crops to laboratory animals for 90 days. The majority of those studies find no significant health problems, but a few hint of possible organ damage and inflammation.
The most incendiary study was published last year by French biologist Gilles-Eric Seralini, an avowed opponent of genetic engineering. It was the first time rats had been fed Roundup Ready corn for essentially their entire life spans. Seralini claimed that animals in the two-year study who ate the GE feed died earlier and were more likely to develop tumors and organ damage.
But other scientists bashed the research, pointing out that Seralini used a strain of rat prone to developing tumors in old age, didn't have enough animals in each group to draw conclusions, and used questionable statistics.
"It's a really bad study," said Marion Nestle, a food safety advocate and professor of nutrition at New York University. Even though she's a strong proponent of GE labeling, Nestle said she didn't believe Seralini's conclusions.
A follow-up is in the works. Whatever the outcome, the need for more long-term studies is clear, said Michael Hansen, a senior scientist at Consumers Union, which is critical of genetic engineering and favors labeling.
People may have been eating GE foods for 20 years without any obvious health effects, but some diseases take decades to develop.