This story was updated on January 27th, 2022. 

Dietary supplement trade association The Council for Responsible Nutrition (CRN) said that it was dissatisfied in the latest response it received from the U.S. Food and Drug Administration (FDA) in an ongoing series of discussions on the legal status of N-acetyl-cysteine (NAC) as a dietary supplement ingredient.
 
The latest response the agency gave, which was received on December 6 by multiple trade associations which submitted unique petitions, did not provide a conclusive determination on the status of NAC, or whether FDA considers it lawful to market NAC as a dietary ingredient. The issue appears to lie in the fact that NAC was marketed as a drug called Mucomyst in the early 1960s, however, it is also a naturally-occurring compound which appears in foods such as onions and garlic.
 
So, CRN filed additional comments restating its position that “the agency should revert to its longstanding policy of allowing manufacturers to market dietary supplements containing [NAC] and rescind the legally invalid position included in warming letters that NAC is precluded […] form being a legal dietary ingredient in dietary supplements.”
 
In its most recent letter, CRN also called attention to the fact that the most recent FDA response was concurrent to its own citizen petition and a petition filed by the Natural Products Association. While both petitions sought the same end, they each requested unique regulatory responses from the agency.
 
NPA’s petition notes that the Dietary Supplement Health and Education Act (DSHEA) includes a “race to market” paradigm which indicates that any article marketed as both a drug and dietary ingredient prior to its passage should be allowed to be marketed as both, as is the case with ingredients like L-carnitine and caffeine. NPA also petitioned FDA to conduct a Part 15 hearing to take place before the commissioner of the agency.
 
CRN’s petition was different; it considers NAC to be an ingredient that should be “clearly grandfathered” in based on the DSHEA provision that an ingredient legally marketed as a dietary supplement prior to 1994 should remain legal. “By introducing concurrent review, FDA appears to be disregarding the legal challenges to the NAC position raised by CRN, and intimating that it has declined CRN’s request for legal review without the agency actually formally stating this,” Megan Olsen, CRN vice president and associate general counsel, said.
 
Beyond this, “FDA is requesting information on safety and current market evaluation that is not relevant to the legal points raised by CRN and not necessary for the agency to address the legality of its position,” CRN wrote to FDA. While Olsen wrote to FDA that NAC’s legal status and safety are “so well established as to be beyond question at this point,” she provided FDA with CRN’s evidence on issues of both safety and legality in the association’s latest response.
 
“The agency’s continued failure to address the singular legal issue on the table is inexplicable,” Olsen said. “Their refusal to act is causing harm to consumers and businesses.”
 
In the midst of challenges regarding NAC, consumers have already found the ingredient unavailable on shelves and removed from mainstream online outlets, including marketplaces and payment processors such as Amazon, Shopify, and PayPal.
 
The association called for the agency to commit to responding to its concerns by Feb. 24, 30 days from the time of its most recent submission.

The American Herbal Products Association (AHPA) also weighed in on the ongoing NAC issue, after submitting its own comments and documentation to FDA demonstrating that NAC has been legally sold as a dietary ingredient prior to the passage of DSHEA.
 
The evidence was sourced from two ingredient suppliers, documentation of four dietary supplements sold prior to DSHEA’s passage, and one conventional food containing NAC. The comments and evidence were submitted to each of the two dockets created for the CRN and NPA petitions, and incorporate AHPA’s earlier arguments for reference.
 
“AHPA maintains a wide-ranging collection of pre-DSHEA records that demonstrate the marketing of ingredients and finished products in the U.S. before 1994,” Michael McGuffin, AHPA president, said. “The AHPA ODI Documents database, coupled with records provided to us by members of the dietary supplements community, made it straightforward to prove that NAC was already sold in the U.S. before the prior drug exclusion provision became law.”