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Genetically modified salmon: food or “frankenfish”?

The Food and Drug Administration (FDA) is close to approving genetically modified (GM) salmon as a food with no significant environmental impact. These fish, popularly dubbed as “frankenfish” in several news reports, produce higher levels of growth hormone. This makes them easier to farm, because they grow much faster than salmon with normal levels of these hormones.

I’ve read some fairly inflammatory and overblown descriptions of this topic–mainly from people who are against GM foods altogether. It’s easy to fall back on naturalist arguments and scare tactics instead of examining the actual evidence.

But there are legitimate concerns. Critics say that the report is lacking. So as skeptics we should always ask: what are the facts? Below I’m going to outline a couple of the concerns about these GM salmon, and evidence for or against their safety.

The fish might escape the farms and outbreed wild populations, causing massive extinctions or creating ecological problems.

The company seeking FDA approval, AquaBounty, is breeding completely female populations, which takes advantage of some facts about salmon biology that won’t be completely described here. The bit of detail I will include is that female breeders are induced to become male and produce sperm that can only create female fish, due to the lack of a Y chromosome.

The company is also attempting to make all of the fish sterile through triploidy. Being triploid means they have too many chromosomes–so while the fish survive, they are effectively sterile. And the fish will be farmed on land, in contained facilities.

Unfortunately, the sterilization process is not perfect and may only work 98% of the time. A couple studies in PNAS [1, 2] suggest that faster-growing fish may outcompete others in the wild, and models show that they could indeed cause extinction of non-GM fish. Indeed, the model suggests that it would only take about 60 GM fish to be released in a population of 60,000 to cause extinction. I am not an expert on these types of models, nor on fish biology–so I’ll leave it at that.

Elevated levels of hormones in the fish may cause health problems in humans.

Reports from the same company suggest that insulin-like growth factor 1 (IGF-1) may be elevated in these salmon. IGF-1 is a potential carcinogen, and may plausibly pose a risk to humans. This, however, does not seem to be addressed in the Environmental Assessment Report–as far as my CTRL + F skills can tell.

I’ll quote from a report [3] by Dr. Michael Hansen, who works for the Consumers Union. Given that it’s actually his job to look at evidence, his review is more thorough than mine–and I suggest you look at it if you’re into knowing facts and looking at scientific references. Note that he uses “GE” below to mean “genetically engineered.” This study does seem suspicious:

The sample size was very small; only 5 GE salmon, 7 non-GE siblings and 5 control fish. The plasma levels of growth hormone in the GE salmon (39.9 ng/ml) was 41% higher than that of their non-GE siblings (28.2 ng/ml) control fish and 95% higher than the control fish, but neither difference was statistically significant, due to the extremely small sample size. Indeed, the sample size was so small, a doubling in growth hormone level in the GE salmon compared to control fish is not statistically significant.

This question might be one that needs to be pursued further.

Given this information, should we be concerned about these genetically engineered salmon? It seems like more evidence is necessary to refute some claims. Given that this would be the first genetically engineered meat to be approved, I believe it should be subject to extra scrutiny–lest worse proposals get approved due to lax standards. However, I also know that the growing global population will need food, and it will likely have to be GM to some extent. As long as the food is safe for human consumption and for the environment, I see no reason to deprive others of the nourishment.

Yesterday, the FDA announced that it is extending its public comment period to April 26, 2013. (It was supposed to end on Feb. 25.) If you are so driven, make your voice heard–whatever your opinion is!


FDA Environmental Assessment Report of AquAdvantage Salmon

FDA website for Genetically Engineered Salmon

[1] Muir and Howard, 1999. PNAS 96(24).

[2] Devlin et al., 2004. PNAS 101(25).

[3] Hansen, Michael. 2010. Comments of Consumers Union on Genetically Engineered Salmon, Food, and Drug Administration Docket No. FDA-201034-N-0001.

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Vy is a recent graduate working in a neuroscience lab with children and monkeys. She likes sewing, knitting, lifting weights, and reading in her free time. Especially reading about science!

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