The Beef War
Moanin' over hormones
Hormonal politics
Nutty, dangerous genes
Guessing game?
Udder woes
To the few who are allergic to them, these exotic fruits are packages that deliver organic allergens.
Photos by Eric Zuelow and David Tenenbaum, © The Why Files.
Beyond sniffles and watery eyes
If you transfer a gene that makes an allergen to a new food, would it trigger the same allergy it did in the source plant? In one of the few pieces of hard evidence about the health dangers of genetic engineering, Stephen Taylor, who studies food allergies at the University of Nebraska, found that moving a gene indeed made a new food allergenic.
It's a half-empty and half-full kind of research finding. On the one hand, it demonstrated one danger of moving genes in food. On the other, it showed how we can predict and prevent hazards.
As the acreage of genetically engineered food crops continues to soar, some scientists have warned that the technology could lead to an increase in food allergies. Already, an estimated 1 to 2 percent of Americans are allergic to some food, and their reactions can be serious or even fatal.
Food allergies are caused by proteins which are made by genes. Indeed, the whole purpose of genetic engineering is to force a plant or animal to make new proteins.
Only chicken feed
Amino acids are the building blocks of proteins, and Pioneer chose the Brazil nut because it contains the 2S protein, which is 18 percent methionine. Knowing that many people are allergic to the Brazil nut, they sent samples to Taylor, who heads the department of food science and technology at Nebraska.
To test whether people allergic to Brazil nuts would respond to the genetically engineered soy, Taylor drew their blood and found that the same antibodies that latched onto Brazil nut proteins also connected to proteins from the engineered soy, but not to normal soy proteins (see "Identification of a Brazil-Nut Allergen..." in the bibliography).
Antibodies play a key role in many allergies. When the allergen gloms on to the antibody, the antibody directs certain cells to release histamine and other chemicals that cause allergic symptoms such as dilation of the blood vessels, increased mucus production, and shrinkage of the airways. In some cases, these familiar allergic reactions can cause a life-threatening systemic reaction called anaphylactic shock.
Let's rewind the tape to the mid-1990s when Pioneer Hi-Bred was testing genetic engineering to increase the level of the amino acid methionine in soybean. A high-methionine soybean would be a boon to chicken farmers who now must buy expensive methionine supplements for their birds.
Hidden dangers
That's not because chickens fed the soybean would be allergenic -- the offending protein would be decomposed in the chicken's gut. It's because soy is used in so many foods that some would almost inevitably end up in human food. This fear has led many to advocate the labeling of genetically engineered food, which is not required in the United States.
The tests caused Pioneer to abandon the Brazil-nut gene and look elsewhere for a high-methionine soy, averting disaster. But testing for allergic reactions to the Brazil nut, which is known to cause allergies is, in hindsight, almost a no-brainer. What about the much larger number of genes originating in sources of unknown allergenicity?
"I don't have a great deal of concern about that," says Taylor. "In nature there are millions of proteins, and only a few hundred allergens, so the chance that something will be allergenic is small." Still, he says it's "prudent" to compare the structure of new proteins to known allergens when genetic transfers are made.
Taylor says existing FDA regulations on transgenic food -- which require manufacturers to assess the risks of genetic transfers in food by answering a series of questions -- are adequate, although there's always room for improvement to reflect new data and techniques.
Here's something to think about: When food is genetically modified, the goal is generally to introduce one new protein. Eating a new food, Taylor notes, "introduces hundreds of new proteins."
He thinks that if food allergies are the concern, the focus should be on new foods, not on genetically engineered ones. "You have to put the risks into perspective. People are going to develop allergies to the stuff they eat, and as they eat a wider variety of foods, they are going to develop a wider variety of allergies."
You think anybody's testing those new foods?
Are allergies the only potential hazard of genetically engineered food? Not!
Does the finding prove that transgenic foods are inherently dangerous? Not really, says Taylor. He agrees that in the Brazil-nut case, "Lives may have been at stake... it would have been a potential disaster to have these on the market."
If Taylor is sanguine about the allergenic risks of genetically modified food, he does look with a bit of alarm on another cause of food allergies: the glut of new foods on grocery shelves. While all the focus is on genetically engineered food, "A much bigger risk is the introduction of entirely new foods, like kiwi fruit," he says. "Nobody in the United States was allergic to kiwi 20 years ago, because nobody ate them here." Now, he says, kiwi has become "one of the most common fruits, and some people are allergic to it."
