Choosing grilled chicken at a fast food joint isn’t the health-conscious choice you might think. For one thing, that piece of chicken doesn’t contain only chicken, as a CBC Marketplace investigation recently found.

The Canadian TV series sent samples of chicken from five different restaurants to a university lab in Ontario for testing, finding that all of them contained significantly less protein than you’d get in a home-cooked piece of poultry.

A piece of unseasoned chicken you buy at the store should be comprised of 100 percent chicken DNA, but tests of grilled chicken from McDonald’s, Wendy’s, A&W’s, Tim Horton’s, and Subway showed much lower levels of bird DNA. Seasoning or marinating would reduce the percentage of chicken DNA in a piece of meat, but Subway, in particular, had a particularly alarming lack of chicken in its chicken.

While all the other restaurants had average values of more than 80 percent chicken DNA, Subway’s samples showed so little chicken DNA that the researchers felt compelled to go get more samples and test them again. The oven-roasted chicken used in Subway’s sandwiches contained an average of 53.6 percent chicken DNA, while the chicken strips used in items like the Subway Sweet Onion Teriyaki sandwich had an average of 42.8 percent chicken DNA in them. Most of the rest of the DNA in the meat was actually soy.

Subway Canada responded to the investigation by saying that the company is “concerned by the alleged findings.”

“Our chicken strips and oven roasted chicken contain 1 percent or less of soy protein,” a Subway spokesman wrote in a statement to CBC. “We use this ingredient in these products as a means to help stabilize the texture and moisture.” The company said it would be looking into the issue with its chicken supplier.

The other grilled chicken options weren’t terribly healthy, either. The tests showed that even after factoring in other ingredients, the fast food options had a quarter less protein than a home-cooked piece of chicken would, and way more sodium (like, up to 10 times more). According to one food scientist CBC spoke to, this is likely because the meat isn’t simple chicken, but a “restructured” product, meaning that it’s made of smaller pieces of meat bound together with other ingredients that make it cheaper or add flavor. What looks like a simple piece of chicken has more than a dozen ingredients—the samples in the study had an average of 16 ingredients. Those ingredients included sugar, a product very few people expect when they order a chicken sandwich.

That doesn’t mean you should swear off chicken sandwiches altogether, but you can stop patting yourself on the back for ordering one instead of a burger.

Update: After the Marketplace study was widely reported on Tuesday, a spokesperson for Subway issued a statement to the Huffington Post vehemently denying the findings. "The accusations made ... about the content of our chicken are absolutely false and misleading. Our chicken is 100 percent white meat with seasonings, marinated and delivered to our stores as a finished, cooked product ... We do not know how [CBC News] produced such unreliable and factually incorrect data, but we are insisting on a full retraction.”

[h/t CBC Marketplace]