Fact check: Social media posts on Subway tuna DNA test lack context

·5 min read

The claim: A new study failed to find tuna DNA inside of a Subway tuna sandwich

Subway is facing criticism on social media, where users are highlighting a recent report about how much tuna is actually in the fast-food chain's tuna sandwiches.

The claim comes amid an ongoing lawsuit that alleges Subway's tuna sandwiches do not contain tuna. Online posts claim a new study came to the same conclusion.

"New study fails to find any tuna DNA inside Subway tuna sandwich: 'We cannot identify the species,'" reads a June 22 Instagram post.

Accompanying the text is a screenshot of a June 22 Complex article headlined, "A Lab Analysis Was Done to Determine Whether a Subway Tuna Sandwich Contained Tuna DNA."

USA TODAY reached out to the Instagram user for comment.

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While it's true that a recent New York Times analysis found no identifiable tuna DNA in a Subway sandwich, the post fails to mention additional context about the test.

What the lab test found

The claim stems from a lab test commissioned by The New York Times that reportedly detected no tuna DNA in tuna sandwiches collected from three different Subway locations in Los Angeles.

The Times purchased the Subway sandwiches, removed the tuna, froze it and shipped it to an unidentified commercial food testing lab. The samples were run through a $500 PCR test, which detects genetic material from a specific organism, to look for any of five tuna types out of 15 species.

According to the report, the lab said it found "no amplifiable tuna DNA was present in the sample." A lab analyst told the paper that this was because either the tuna was too heavily processed, or there was actually no tuna.

There are other factors to take into consideration, such as how tuna DNA becomes denatured once it is cooked, making it difficult to identify a fish's characteristics.

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The Times also notes that "a handful" of commercial labs declined to test the tuna samples, citing technical limitations and company policies.

Subway denies the claims

Subway has denied allegations that its sandwiches do not contain tuna, and a different lab test concluded the sandwiches do contain tuna.

"DNA testing is simply not a reliable way to identify denatured proteins, like Subway’s tuna, which was cooked before it was tested," Lorri Christou, vice president of public relations, communications and public affairs at Subway, told USA TODAY.

"Unfortunately, various media outlets have confused the inability of DNA testing to confirm a specific protein with a determination that the protein is not present," she said in an emailed statement.

Christou added that the Times report does not show there is not tuna in Subway's tuna, but that the testing could not confirm tuna, "which is what one would expect from a DNA test of denatured proteins."

The Times article notes that cooking tuna likely destroys the fish's characteristic properties, "making it difficult, if not impossible, to identify." The Instagram post does not mention this.

Additionally, the Jan. 21 lawsuit filed by plaintiffs Karen Dhanowa and Nilima Amin does not include specific evidence to support their claim that Subway sandwiches do not contain tuna, according to NBC News. The plaintiffs also did not test tuna in the sandwiches they actually ate.

Subway issued a statement on Jan. 28 in response to the lawsuit, stating it delivers "100% cooked tuna to its restaurants."

In a June 7 court filing, the plaintiffs amended their original complaint and now accuse the restaurant chain of misleading customers by promoting its product as "100% sustainably caught skipjack and yellowfin tuna," according to TODAY.

"Just like the original claim, the new claims are untrue and have absolutely no merit," Christou told USA TODAY. "In fact, the amended complaint does not remedy any of the fundamental flaws in the plaintiffs’ case that should result in the case being dismissed."

Subway's website says it only sells skipjack and yellowfin tuna "sourced from fisheries with non-threatened stock levels."

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In February, Inside Edition reported that it sent tuna samples from three New York Subway stores to a lab in Florida that specialized in conducting DNA testing of fish. The test found tuna in all samples received.

Our rating: Missing context

The claim that a new study failed to find tuna DNA in a Subway tuna sandwich is MISSING CONTEXT, based on our research, because it lacks important details. The claim is based on a New York Times independent analysis, in which a reporter froze and shipped Subway tuna samples to a lab for analysis.. The lab tested for five tuna species (out of 15) and concluded that the tuna was too processed or that there was no tuna DNA. Different tests have detected tuna in Subway sandwiches, and experts say canned tuna becomes denatured when cooked.

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This article originally appeared on USA TODAY: Fact check: Online post on Subway tuna DNA report is missing context

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