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Genetically Engineered Salmon: FAQ

Frequently Asked Questions on Genetically Engineered Salmon as the FDA Weighs Approval

By Daniel J. DeNoon
WebMD Health News

Reviewed By Laura J. Martin, MD

Sept. 22, 2010 -- Is genetically engineered salmon safe to eat? What effects will the altered fish have on the environment? What the heck is a genetically engineered salmon, anyway?

The FDA's pending decision on whether to approve genetically engineered salmon -- and whether it should be labeled -- has spawned many questions. WebMD provides answers.

What Is Genetically Engineered Salmon?

Genetic engineering isn't new. For thousands of years, humans have used selective breeding to raise crops and livestock with desirable traits.

Modern technology now gives scientists -- and the industries that employ them -- the ability to directly alter the genetic structure of plants and animals. This is done by inserting desirable DNA sequences directly into the genome.

This already is done in a large number of vegetable crops. But now a company called AquAdvantage wants to do it in salmon. If the FDA gives the green light, it will be the first genetically engineered animal sold as food.

The Atlantic salmon that AquAdvantage would produce are exactly the same as other farmed Atlantic salmon except for one thing. They carry a DNA switch that freezes a growth-hormone gene in the "on" position. This causes overproduction of growth hormone, making the fish grow much faster than normal farmed salmon.

How Do Genetically Engineered Salmon Differ From Normal Farmed Salmon?

They are almost exactly the same.

AquAdvantage genetically engineered salmon differ from normal farmed salmon only in their speed of growth -- and in how much growth hormone they produce. But they are not like wild salmon.

Both "normal" farmed salmon and genetically engineered salmon are manipulated in a number of ways that improve farming yield but which make them very different from wild salmon.

Are Genetically Engineered Salmon Safe to Eat?

Probably. An FDA analysis concludes that genetically engineered salmon is just as safe as normal farmed salmon. But nagging questions remain. An analysis by a Consumer Union scientist, for example, concludes that far more information is needed.

There are two basic differences between normal farmed salmon and genetically engineered salmon: The altered salmon grow much faster, and they make more growth hormone.

As long as the genetically engineered fish are raised in a healthy manner, their speed of growth does not appear to be a problem in and of itself.

But safety data analyzed by the FDA looked only at AquAdvantage salmon grown at a Canada facility. Critics say there is no data from the Panama facility at which the firm intends to produce most of its fish.

Different questions are whether the insertion of the DNA switch causes a safety problem -- and whether the extra growth hormone in the genetically engineered fish will cause problems.

The FDA analysis suggests that the DNA switch itself doesn't make the fish unsafe. And it concludes that the level of growth hormone in the altered fish is not especially worrisome.

Critics say more study is needed to see whether other salmon proteins are affected by the altered switch. But their main concern is over whether the increased growth hormones make the fish more likely to trigger allergies.

People allergic to fish generally avoid salmon anyway. But some critics say that if the genetically engineered salmon is more allergenic than other fish, it might provoke fish allergies in people who were not already allergic to fish.

In comments to the FDA panel, Consumer Union senior scientist Michael Hansen, PhD, was highly critical of the FDA's analysis of the allergy question.

"Because the FDA's assessment is inadequate, we are particularly concerned this salmon may pose an increased risk of severe, even life-threatening allergic reactions to sensitive individuals," Hansen said.

One of the outside experts on the FDA panel advising the FDA, Craig Altier, PhD, DVM, of Cornell University, says he's not worried about the allergy issue.

"Exhaustive analysis by the FDA showed no difference from conventional salmon," Altier noted in a news release. "The growth hormone itself presents no specific risk, as we consume growth hormone in all the meats we eat."

Is Genetically Engineered Salmon Safe for the Environment?

The theoretical problem with genetically engineered salmon is that some of them might escape and breed with wild salmon, polluting the wild salmon gene pool and threatening the species. There's also a threat that the fast-growing fish might become an invasive species, pushing native species out of their environmental niche.

The FDA analysis concludes that this is an extremely small risk:

  • Genetically engineered salmon are almost all sterile females.
  • Genetically engineered salmon, like other farmed salmon, have abnormalities that aren't a problem on a fish farm but which likely make the fish unlikely to thrive in the wild.
  • Because they grow so fast, genetically engineered salmon need high-energy feed that they cannot get in the wild, making it harder for them to thrive there.
  • Genetically engineered salmon are raised in inland tanks.
  • The waterways near AquAdvantage salmon farms are not hospitable to salmon.

But others -- including FDA advisory panelist Craig Altier, PhD, DVM, of Cornell University -- warns that escape of the fish into the wild could be an environmental disaster.

"The release of this fast-growing animal could have devastating effects on native fish populations," he warns. "To protect wild fish stocks, [facilities raising genetically engineered salmon] would require the utmost security, rigorous inspections, and constant oversight by the FDA."

If Genetically Engineered Salmon Is Approved, How Can I Tell It From Normal Farmed Salmon?

That's an open question. If the FDA determines that genetically engineered salmon is essentially identical to normal farmed salmon, it may lack the authority to require a special label.

However, a number of consumer groups strongly oppose the sale of genetically engineered salmon without specific labeling.

SOURCES: FDA, Briefing Packet, Veterinary Medicine Advisory Committee, Sept. 20, 2010.

News release, Cornell University, Sept. 21, 2010.

News release, Consumers Union, Sept. 17, 2010.

Hansen, M. Comments of Consumers Union on Genetically Engineered Salmon, Sept. 16, 2010.

WebMD Health News: "FDA Debates Labels for Sale of Genetically Engineered Salmon."

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