If you’re about to go get some lunch, you might want to stop and read this first.

DNA analysis has been carried out on a selection of popular chain restaurants in Canada and some of the results aren’t too tasty. The investigation by CBC Marketplace, with the help of researcher Matt Harnden from Trent University's Wildlife Forensic DNA Laboratory, tested the chicken in sandwiches and wraps from five restaurants in Peterborough, Ontario.

Most shocking all of, their results found “Oven Roasted Chicken Sandwich” and the “Sweet Onion Chicken Teriyaki strips” from SUBWAY contained an average of 53.6 percent and 42.8 percent chicken DNA, respectively.

Harnden found that most other scores were “very close” to 100 percent chicken DNA. According to their analysis, McDonald's Country Chicken Grilled averaged 84.9 percent chicken DNA, Tim Hortons Chipotle Chicken Grilled Wrap averaged 86.5 percent, Wendy's Grilled Chicken Sandwich averaged 88.5 percent, and A&W Chicken Grill Deluxe averaged 89.4 percent.

So what is the other non-chicken DNA found in these samples?

While a chunk of pure chicken meat would contain 100 percent chicken DNA, you can expect it to be a little under that in processed meat because of the addition of seasoning, marinating, etc and the fact that a lot of processed meat is “beefed up” with fillers such as soy or water.

Subway Canada disagree that the figure is actually that high, nevertheless, they replied to CBC Marketplace saying they will investigate their supply chain in light of these findings.

Their statement read: “SUBWAY Canada cannot confirm the veracity of the results of the lab testing you had conducted. However, we are concerned by the alleged findings you cite with respect to the proportion of soy content. Our chicken strips and oven roasted chicken contain 1% or less of soy protein. We use this ingredient in these products as a means to help stabilize the texture and moisture. All of our chicken items are made from 100% white meat chicken which is marinated, oven roasted and grilled.”

So while you don’t need to necessarily freak out that this DNA from another animal, it can be evidence your food is low quality or perhaps not as healthy as the marketing makes it seem.

Update 01/03/2017: In an emailed statement to IFLScience, Subway said they completely refuted the scientific DNA evidence which CBC Marketplace reported.

They said: "The accusations made by CBC Marketplace about the content of our chicken are absolutely false and misleading. Our chicken is 100% white meat with seasonings, marinated and delivered to our stores as a finished, cooked product.

We have advised them of our strong objections. We do not know how they produced such unreliable and factually incorrect data, but we are insisting on a full retraction. Producing high quality food for our customers is our highest priority. This report is wrong and it must be corrected."