In early 2014, a blogger known as Food Babe launched a petition pushing sandwich chain Subway to remove an obscure chemical also used in yoga mats from its bread. Two days and more than 78,000 signatures later, Subway announced it was taking out azodicarbonamide - the yoga-mat chemical, as it came to be known.

Since then, a number of other major fast-food chains have followed suit, sans petition or fanfare.

McDonald's and Wendy's, which all used the chemical in their breads in 2014, have since gotten rid of it entirely.

"We removed these items because it was the right thing to do and it was a concern for our customers," a McDonald's spokesperson said.

Advertisement

But the company didn't mention the bread additive's removal in a press release this week announcing several other ingredient overhauls, including the removal of high-fructose corn syrup from buns and artificial preservatives from McNuggets.

Azodicarbonamide is a commonly used dough conditioner that is also found in yoga mats, as well as in flip-flops and packing insulation, because it makes them both lighter and stronger, according to the Environmental Working Group, an advocacy group.

The Food and Drug Administration has approved its use in food in limited amounts, but the European Union has banned its use in food.

The World Health Organisation has linked it to asthma, and the industry watchdog group the Center for Science in the Public Interest has cited potential links to cancer, especially in high doses.

At Dunkin' Donuts, it's now out of the croissants and danishes, and while it's still in the Texas toast, a spokesperson said the chain is testing a new, azodicarbonamide-free version. At Burger King, the additive remains only in the French toast sticks.

"Good riddance," said Michael Jacobson, executive director of CSPI, "but if you're thinking of health, it's only a tiny step forward." (He says sodium and calorie counts are bigger concerns.)

McDonald's, Dunkin' Donuts, and Wendy's each separately said they reformulated their breads in response to consumer preferences.

Asked about the lack of publicity, a spokeswoman for the National Restaurant Association said, "That would be more of a question for the brands specifically." But she said consumer concerns are driving trends toward less-processed ingredients.

Not everyone chalks up the lack of hoopla to humility. "They don't want to bring unnecessary attention to their ingredient decks," said Vani Hari, the blogger whose petition prompted Subway to cut the chemical from its bread.

More scrutiny, she argued, would only prompt further demands for changes - not congratulations for the changes that have been made. After her 2014 petition, Subway's efforts at damage control went beyond reformulation and included a TV commercial, even after the chemical was removed.

"A brand is really a collection of associations in people's minds," said Daryl Weber, a consultant for such companies as Coca-Cola and PepsiCo's Gatorade unit and author of a book, Brand Seduction: How Neuroscience Can Help Marketers Build Memorable Brands, that explores the science of successful brands. "You don't want one of those associations to be, 'We used to have the yoga-mat chemical in our food.' "

There's also the fear of being caught behind the curve by removing the chemical late in the game, restaurant consultant Aaron Allen said.

"It's kind of like turning your homework in late," he said, "trying to slip it in and hoping nobody notices."