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Genetically engineered (GE) foods are in the headlines again. Last month, a controversial French study claimed that a particular strain of GE corn causes cancer in lab rats. And in next week’s election, Californians will vote on Proposition 37, which aims to require labeling for all genetically engineered foods.
So do GE foods truly pose a health threat to humans? Does mandatory GE labeling make sense? We take a look at what the science says.
The Lowdown on Genetically Engineered Foods
GE foods are often referred to as genetically modified organisms (GMOs), but that term is incorrect, explains Alison Van Eenennaam, Ph.D., a genomicist and biotechnologist at the University of California, Davis. All foods have been genetically modified in some way, whether through engineering in a lab or through traditional selective breeding in the field.
GE foods have been genetically altered to give them a new, favorable characteristic, including pest or viral resistance or an improved nutrition profile. In some cases, scientists splice in DNA from another species that codes for a beneficial trait. In others, specific genes are essentially turned off so that they don’t code for an unwanted trait.
For now, the only GE foods on the market are plants and microbes. Commercial GE plants include pest- or herbicide-resistant crops, such as corn and soy, and viral-resistant papaya and zucchini. GE microbes include an engineered curdling agent for vegetarian cheese to replace rennin, an enzyme that comes from the stomachs of cud-chewing animals used to make some cheeses, as well as engineered yeasts used to ferment some wines.
Today, the most widespread GE foods are pest- and herbicide-resistant crops, according to Van Eenennaam, which mainly come from multinational corporations including Monsanto, DuPont and Syngenta. And for now, these are the GE foods that have stirred up the biggest controversy.
The most common pest-resistant crops have been modified with bits of DNA from Bacillus thuringiensis (Bt), bacteria that naturally produce proteins that are fatal to a specific group of insects, including major crop pests, but are not toxic to mammals. Bt-based insecticides have been used in both conventional and organic farming since the 1950s in the U.S. and are still sprayed on crops today.
The most common herbicide-resistant plants also include major crops such as corn and soy. These have been genetically altered to withstand a specific type of herbicide (mostly Roundup Ready), which kills weeds while leaving the crop alive. Between 75 and 80 percent of processed foods in the U.S. include some sort of GE crop, according to the Grocery Manufacturers Association
What’s the Worry?
When it comes to health and GE foods, most consumers are worried about the possibility of allergens or toxins. Many also have concerns over the crops’ environmental impact or have a general distrust of the multinational corporations that control the crops (but those are topics for another time).
Allergic reactions and toxicity are also the main concerns both for the scientists who develop new GE foods and those who study food allergies and toxins, explains Bruce Chassy, Ph.D., a food scientist and professor emeritus at the University of Illinois at Urbana-Champaign. All plant breeding, whether engineered or conventional, poses the risk of producing a plant that is allergenic, toxic or has other unwanted traits, according to a 2004 National Academy of Sciences (NAS) report on GE foods and human health, which ultimately determined that GE crops are safe.
But GE crops must jump through regulatory hoops that conventional crops do not, which means potentially dangerous traits are weeded out, making GE “the most researched and regulated food on the market,” says Chassy.
Over the past two decades, adds Chassy, hundreds of studies have convinced major scientific societies including the NAS and the American Medical Association that GE crops “pose no new or different risks than any other crop, and there is no scientific reason to believe they would be any more risky.”
Fear of Allergies
Most consumer concerns regarding allergies center on Bt crops and whether eating proteins that the bacterial DNA produces will lead to new food allergies. It’s not so far-fetched considering that most food allergies are an abnormal immune response to a protein, according to Stephen Taylor, Ph.D., a food toxicologist from the University of Nebraska-Lincoln. But as with all potential GE crops, the Bt protein was compared to an extensive database of all known allergen proteins before it was introduced to the marketplace and matched none.
Bt is also present in very small quantities in the edible parts of Bt crops and degrades after it is cooked, further decreasing the likelihood of an allergic reaction, adds Chassy. And there is no widespread evidence of Bt-related allergies over the 60 years that Bt insecticides have been used on conventional and organic crops.
The larger public health problem, according to both Chassy and Stevens, comes from a lack of public understanding of the eight major sources of food allergies, which include the most common foods in our diet: milk, egg, peanut, tree nut, fish, shellfish, wheat and soy.
Do GE Foods Cause Cancer?
In September, a new and widely-panned toxicity study claimed that Roundup Ready corn and herbicide caused tumors in rats. The paper was met with extensive criticism throughout the scientific community, including a negative review from the European Food Safety Authority. Major critiques noted that the study did not follow OECD guidelines for testing chemicals, the standard for toxicity tests; that the rats used in the test are known for developing spontaneous tumors, which means the tumors in the experiment may not have been due to the corn; and that the group failed to publish all of their data.
The paper’s authors also tried to manipulate science journalists into one-sided coverage by asking them to sign confidentiality agreements in order to cover the work.
Not only was the study flawed, it was also not the first to look at the long-term effects of GE crops on animals. To date, at least 25 long-term, multigenerational animal studies have shown no evidence of GE crop toxicity, notes Marcel Kuntz, Ph.D., a biologist at the French National Center for Scientific Research, co-author of a recent literature review of the studies and author of a website that collects scientific studies on GE foods.
To Label or Not to Label
Between the fears of allergies and toxicity, it’s no surprise that some consumers want to know if the foods they’re eating have been genetically modified. California’s Prop 37 ballot initiative, if approved by voters, will require labels on products that have ingredients made through genetic engineering. It will also make it illegal to put labels on GE or processed foods indicating they are natural. Proponents argue it is simply a matter of the consumer’s right to know what is in their food.
The Legislative Analyst’s Office, a nonpartisan fiscal policy advisor to the California legislature, suggests the program’s annual cost could run the state “from a few hundred thousand dollars to over $1 million” for regulation. Economists from the University of California, Davis suggest it will cost food processors an additional $1.2 billion annually (this research was, in part, funded by a group opposed to Prop 37). An industry report claims this will translate to an additional $350 to $400 in grocery bills per Californian family per year, although not everyone agrees.
Numbers and intentions aside, there is the issue of what information the labels would relay. Currently, mandatory labels provide information about the food’s contents, including calories, and alerts to the presence of common food allergens. Despite Prop 37’s intention to provide more information on food content to consumers, the proposed GE label provides no information about the contents of the food; rather, it focuses only on the process by which it was made.
“I don’t like process-based labels,” says Alan McHughen, a plant biotechnologist and geneticist from the University of California, Riverside, echoing the opinions of Van Eenennaam and Kuntz. “I fully support the current labeling regime that we have nationally where composition of the food is paramount.” Even if allergens were a concern in GE foods, McHughen adds, the proposed labels wouldn’t indicate which foods contain Bt crops and which contain other types of GE-made ingredients. Instead, they would simply indicate that genetically engineering was used at some point in making the product.
“Prop 37 is supposed to provide information to consumers so they can make an informed choice,” says McHughen, referring to the fact that other common food processes, including organic production, ionizing radiation or carcinogenic chemicals have no similar required labeling. “But if processed based labeling is such a good idea, why is it limited to genetically engineered food for one thing, and then only to a small set of those genetically engineered foods? If labeling for process is such a good idea, why is it so limited in scope?”
Regardless of whether genetically engineered foods will one day require labels, if you’re concerned about GEs, go organic. A 2012 report from the Council on Science and Public Health, which notes no significant difference in the contents of GE versus traditional foods, points out that consumers who want to avoid GE foods already have that option by choosing foods labeled “USDA Organic.”
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