How can the FDA tell whether genetically modified fish are safe?

Answers to your questions about the news.
Sept. 21 2010 6:33 PM

How Can the FDA Tell Whether GMO Fish Are Safe?

With a blender, of course.

Genetically modified salmon: dangerous or delicious? Click image to expand.
Genetically modified salmon: dangerous or delicious?

The Boston-based company AquaBounty has engineered a faster-growing, cold-resistant salmon by splicing in genes from other fish, and now the FDA is holding hearings on whether to allow this genetically modified creature into your grocer's freezer case. How do you prove that a GMO fillet is safe to eat?

Compare it to regular fish. If you wanted to sell a completely novel chemical compound as food—say, a newly developed preservative—you would have to spend years feeding the stuff to laboratory animals, waiting for ill effects. By international consensus, however, genetically modified foods do not have to go through this process. All the manufacturer has to prove is that the altered species does not differ, biochemically, from its safe-to-eat, naturally occurring cousin in any way that would impact human health.

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To gather such proof, AquaBounty analysts started by freezing a few samples of their genetically altered salmon and extracting proteins. They compared the proteins to reference data on unaltered salmon in the FDA's Regulatory Fish Encyclopedia, which classifies 1,700 commonly consumed species by size, shape, color, and biochemical properties. Lab technicians also conducted blood tests. (These indicated that one particular growth-promoting protein was elevated in the new salmon, but not so much that it would make you sick.) Finally, they homogenized the fillet samples in a blender, and analyzed them for fat, protein, carbohydrates, and a host of vitamins and minerals. The tests showed that only vitamin B6 content differed significantly, but still not enough to raise concerns.

Not everyone likes these tests. Opponents argue that we just don't have a firm grasp on the subtle changes that genetic engineering can cause. They point to a recent experiment that suggested that genetically modified soy beans might sterilize hamsters after three generations. (It also seemed to promote hair growth in their mouths and turn their testicles blue.) But studies like this are rare and possibly the result of contaminants like herbicides. There is no indication at this point that the FDA will require genetically modified organisms to go through feeding studies.

Got a question about today's news? Ask the Explainer.

Explainer thanks Siobahn DeLancey of the FDA and Gregory Jaffe of the Center for Science in the Public Interest.

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Brian Palmer writes about science, medicine, and the environment for Slate and the Natural Resources Defense Council. Email him at explainerbrian@gmail.com. Follow him on Twitter.

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