(CNN) Got milk? If you're buying "milk" made with non-dairy products like almonds or oats, the US Food and Drug Administration isn't so sure you do.

During a the Politico Pro Summit on Tuesday, FDA Commissioner Dr. Scott Gottlieb questioned whether the "standards of identity" applied to milk in the United States are being enforced correctly.

The FDA describes milk as "the lacteal secretion, practically free from colostrum, obtained by the complete milking of one or more healthy cows." That definition doesn't leave room for vegan alternatives to call themselves "milk," though a number of products on the market do.

Non-dairy milks, including soy, almond, rice and coconut milk, are juices from nuts, seeds, grains and legumes that may be fortified with vitamins and minerals to deliver the equivalent nutrient profile and sometimes taste and consistency of cow's milk.

The agency is not commenting on its plans or Gottlieb's observation that the government is "probably not" enforcing its own standard of identity for milk, but FDA press officer Deborah Kotz said that "food names inform consumers about what they're buying, and standard of identities ensure that food meets certain standards in terms of what's in it."

The National Milk Producers Federation argues that those standards are not being enforced correctly. Gottlieb's comments come after the foundation ratcheted up its lobbying efforts.

Chris Galen, senior vice president of communications for the federation, said the organization has doubled down on its work in the past 18 months, not simply because the FDA got a new commissioner but because "plant-based imitation products" seem to be growing in popularity. He cites the existence and widespread availability of not only almond- and soy-based drinks but those made of hemp, flax, quinoa and even potatoes.

Though cows are mentioned in the definition, federal standards also allow for "milk" to be produced from other animals but not from vegetable or plant products, Galen said. Dictionary definitions are also broader and make allowances for nuts, which could eventually lead to legal action from producers of non-dairy beverages if the FDA begins enforcing the standard.

Kotz noted that "Many (standards of identity) have existed for decades and at the time they were developed, the FDA could not foresee the types of new products that would be developed in the future using different ingredients and/or manufacturing processes."

To the foundation, the producers of these beverages want to co-opt the "positive reputation" and "health halo" associated with milk.

Though non-dairy beverages are often substituted for cow's milk, "they are not able to completely mimic the nutritional profile," according to Vandana Sheth, a registered dietitian and spokeswoman for the Academy of Nutrition and Dietetics. Rice milk, coconut milk and almond milk provide minimal amounts of protein compared with dairy milk, and if the alternatives are not fortified with vitamins such as calcium, D and B12, you might be missing those, too.

To put it bluntly, "milk" sounds better than "nut juice," Galen said, acknowledging that it makes sense that companies would rather their products be identified with the former option.

Producers of popular non-dairy drinks, though, say that the enforcement of the standards is sufficient and that their products are correctly labeled as "milk."

"In the United States, 'soymilk,' 'almondmilk,' and 'coconutmilk' are the common and usual names for plant-based products under the current meaning of FDA regulation, and we communicate on our products with clear references," said Michael Neuwirth, senior director of external communications for Danone North America, which owns non-dairy milk brand Silk.

"Dairy and plant-based products are clearly labeled with nutrition facts so people know what's in the products and can choose the ones that best fit their dietary needs and preferences. We do not believe further labeling standards are necessary."

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Galen argues that some brands, like Oatly, sell their products without a "milk" label overseas and face no adverse consequences.

Whether Silk and its American contemporaries will have to follow suit remains to be seen, but Galen says he and his organization hope "the FDA will hold these plant-based marketers to the law" while making room for them in the market.

"We're not saying these imitation plant-based products don't have a role in the marketplace," he said, noting that he understands the usefulness of non-dairy beverages for consumers with dietary, religious or ideological restrictions, "but the products have to be labeled as they are."