“The question becomes, have we been enforcing our own standard of identity,” Gottlieb said about “milk” at the Politico event Tuesday. “The answer is probably not.”

Standards of identity have been the source industry spats as American diets have evolved, including fights about what gets to be called mayonnaise and yogurt. More recently, there are disagreements over what to call meat grown by culturing cells, a science that’s still emerging.

The FDA can’t just change the way it enforces a standard without warning, Gottlieb said. Since it plans to take a different approach to enforcement, he said the FDA will have to first develop guidance notifying companies of the change and ask for public comment. That guidance will probably be issued in a year, he said.

Gottlieb said the agency expects to get sued, since dictionary definitions are broader and say milk comes from a lactating animal or a nut.

The National Milk Producers Federation said it welcomes Gottlieb’s recognition that the labelling practices of many “plant-based dairy imitators” violate federal standards. The industry group had recently renewed its push for the FDA to crack down on non-dairy drinks calling themselves “milk.”

The Good Food Institute, which advocates for plant-based alternatives, says the term “milk” should be permitted with modifiers for non-dairy drinks.

“For the same reason that you can have gluten-free bread and rice noodles, almond milk and soy milk are the most clear and best terms for describing those products,” said Bruce Friedrich, the group’s co-founder.

The FDA declined to comment on whether the agency would enforce other standards, such as for yogurt.