Tag Archives: gmo

Genetically-Modified Salmon are Safe to Eat: Here’s How We Know

by Joseph DeSisto

One of the biggest news stories of today was the approval by the Food and Drug Administration of a genetically modified salmon for human consumption. This particular fish goes by the trademarked name “AquAdvantage,” and was developed by the company AquaBounty Technologies.

The approval is a big deal because, although scientists have been genetically modifying animals for many years, the AquAdvantage salmon is the first such animal ever to be approved for sale as food in the United States. Not surprisingly, this has inspired quite the outcry from anti-GMO advocacy groups.

One of their concerns is what will happen should these fish escape into the wild. The FDA had that same concern, which is why all AquAdvantage fish are sterile females, incapable of breeding with each other or with wild Atlantic salmon.

Of more immediate concern, however, is whether AquAdvantage salmon are truly safe to eat. Although the FDA claims this is the case, I am not an especially trusting person. I studied the data behind their claim to see whether I would reach the same conclusion.

Is AquAdvantage salmon safe to eat?

The FDA consumer fact sheet claims:

“After an exhaustive and rigorous scientific review, FDA has arrived at the decision that AquAdvantage salmon is as safe to eat as any non-genetically engineered (GE) Atlantic salmon, and also as nutritious.”

Because most people don’t like graphs, tables, and any phrase starting with the word “statistical,” the fact sheet does not include the actual data. The data is, however, available under the Freedom of Information Act and you are free to study it by reading the FOI summary. It is long and tedious, so I will summarize.

The AquAdvantage salmon is the result of adding two genes into the DNA of a normal Atlantic salmon egg. One of these genes produces growth factors, hormones that cause the fish to grow twice as fast as a typical Atlantic salmon. The growth gene comes from a closely related species, the Chinook salmon, which is similar to Atlantic salmon but grows to be much larger — up to 130 pounds.

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Chinook salmon can grow to 58 inches long and weigh up to 130 pounds. Photo by D. Ross Robertson, licensed under CC BY-NC-SA 3.0.

Another gene is needed to make sure the growth gene is kept turned on in AquAdvantage salmon — otherwise the salmon might fail to produce Chinook growth factors. That second gene comes from another fish, an eelpout, and it simultaneously promotes the growth gene while also producing anti-freeze proteins, which make the salmon more cold-tolerant.

When the FDA says that a food product is safe, they “mean that there is ‘a reasonable certainty in the minds of competent scientists that the substance is not harmful under the intended conditions of use.*’” In this case there are several substances: the DNA, plus the molecules and hormones the DNA is supposed to make. Fish DNA by itself is not dangerous to humans – you cannot absorb it into your own genome, and it isn’t toxic. DNA is just DNA. It’s in all living things, modified or otherwise.

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An eelpout. Photo copyright: President and Fellows of Harvard College, licensed under CC BY-NC-SA 3.0.

So the new question is, are the gene products unsafe for humans to eat? The eelpout’s anti-freeze proteins are already used in many other foods, including ice cream, so we will focus on the growth factors. The factor in this case is simply growth hormone (GH).

Atlantic salmon produce their own GH, just like all fish. And you eat them, anytime you eat salmon. If you’ve eaten Chinook salmon, you’ve also eaten Chinook GH. Although Chinook salmon are endangered in the wild, they are farmed just like Atlantic salmon and sold in U.S. markets every day – approved by the FDA and safe to eat.

How do we know?

Still scientists, funded by AquaBounty, chemically analyzed the meat and skin of AquAdvantage salmon and compared their results with ordinary, farm-raised salmon. Because farm-raised salmon are already fed supplemental GH (without being genetically modified), they compared these two with farm-raised salmon that were purposefully not given any additional hormones.

The result: statistically, modified salmon do not have higher levels of GH than ordinary farm-raised fish. As an aside, both had higher levels than fish which were not fed additional GH.

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Juvenile Atlantic salmon (Salmo salar). Around 2/3 of salmon consumed in the U.S. comes from this species. Photo by Perhols, licensed under CC BY-SA 3.0.

GH itself is safe, but it can trigger the production of another molecule, insulin-like growth factor (IGF1), which can be toxic at high levels. To determine if there were high enough levels of IGF1 in AquAdvantage fish to warrant concern, FDA (not AquaBounty) scientists conducted their own study, a margin of exposure (MOE) assessment. Basically they tested salmon (modified and farm-raised, Atlantic and Chinook) to determine their maximum IGF1 levels. Then they calculated how much of this stuff you would have to eat before you might suffer ill effects.

The biggest fish-lovers in the U.S. eat around 300 grams of fish every day. To be safe, the FDA assumed that all 300 grams consisted of salmon, 2/3 of which (200 grams) was expected to be Atlantic salmon. They also assumed that IGF1 was always present at its maximum known level in AquAdvantage fish.

Say you are one of these obsessive salmon-lovers, but you are wary of GMOs, so you eat 200 grams of unmodified Atlantic salmon per day. Given the chemical analysis of salmon meat and skin, you would consume roughly 2.4 micrograms (0.0000024 grams) of IGF1. If, on the other hand, you only ate AquAdvantage fish, you would find yourself taking in 3.7 micrograms (0.0000037 grams) of IGF1 every day. For comparison, IGF1 levels of 1120 grams or higher are considered unsafe.

In other words, you would be eating too much IGF1 if you ate 66 kilograms (146 pounds) of genetically modified Atlantic salmon in a single day – or 102 kilograms (225 pounds) of non-modified, farm-raised salmon. No one likes fish that much.

Why are you writing about this?

This article started as a letter to a friend who shared an ad (via Facebook) on the FDA approval. This particular ad was misleading. My friend cares very deeply about environmental ethics, food safety, and the truth. I know he did not intend to misrepresent facts, so I wanted to try and clarify the issue from a scientific perspective. As I waded through FDA reports, legal documents, and old petitions, my message to a friend grew and evolved into the article you have just read.

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A misleading advertisement by GMO Free USA.

The ad above comes from GMO Free USA, an advocacy group that seeks to “harness independent science and agroecological concepts to advocate for sustainable food and ecological systems.” They also envision a world “fully protected from GMO contamination.”

Advocating caution in developing new technology is, by and large, the right thing to do. Twisting the facts to inspire fear, however, is not, and this case caution was duly exercised.

The AquAdvantage fish was developed more than two decades ago, and AquaBounty nearly went out of business while waiting for FDA approval. When the FDA finally did approve, they didn’t “think you’re too busy to notice.” Everything you just read came from the Freedom of Information report, publicly available online here. The FDA’s press release on this subject was covered by major U.S. news organizations (with varying levels of objectivity) – The New York Times, CNN, ABC News, and many others.

There is no mandatory labeling of GMOs, but non-genetically modified fish will very likely be labeled (at the discretion of the companies selling them) — and if you only want to eat those salmon, that’s a choice you are free to make. You can also choose not to eat farm-raised salmon, or not to eat Atlantic salmon, thus avoiding any contact with GMOs since they would all have to be farm-raised Atlantic salmon.

Caution and skepticism are good things, and you are free to avoid genetically modified foods for ethical, personal, philosophical or religious reasons. Yet having studied the data, I can at least tell you there are no scientific reasons to panic over the FDA’s approval of AquAdvantage salmon.

*Here the FOI report is quoting the definition of food safety by Guidance for Industry 187: Regulation of Genetically Engineered Animals with Heritable Recombinant DNA Constructs. A Guidance for Industry is sort of like a public fact sheet, but for businesses – it explains the law in a (slightly) more readable format.