DENVER, Aug. 16 (UPI) -- A roomful of natural products professionals and cannabidiol entrepreneurs heard the bad news in Denver on Friday from a government spokeswoman: The U.S. Food and Drug Administration still considers CBD a prohibited substance in any food or dietary supplement for humans or animals.

In a city that sells CBD-infused beer, kombucha and dog treats, Cara Welch, a senior adviser in the FDA's Center for Food Safety and Applied Nutrition, told attendees at an American Herbal Products Association conference that the FDA also was concerned about unsubstantiated health claims that CBD cured everything from Alzheimer's disease to cancer.

"It is prohibited to add CBD to food," Welch said. "There is still a significant amount of missing data to better understand the effects on human exposure and the long-term effects of regular consumption," Welch said.

Some studies show some toxic effects on the liver in high doses, and there is inadequate research about the use of CBD by pregnant or nursing mothers or people with low immunity, she said.

The FDA has approved CBD as an ingredient in four drugs that have gone through the agency's review process. Three are appetite-enhancing and anti-nausea medications for patients with cancer or HIV: Marinol, Syndros and Cesamet. The other drug is Epidiolex, an anti-seizure drug.

In May, the FDA held a public hearing and received almost 4,500 comments on CBD. The agency has formed a hemp working group that is looking at regulatory pathways to move forward on the rules for CBD, Welch said, but there is still not enough data to make a determination.