Consumer Access & Industry Advocacy
What is NAC?
N-acetyl-L-cysteine (NAC) is a derivative of the amino acid L-cysteine and a precursor to the powerful antioxidant glutathione. NAC is widely recognized for its antioxidant and mucolytic properties and is used as a prescription drug to treat acetaminophen (Tylenol) overdose and to help clear mucus in respiratory conditions. NAC has also been marketed in the U.S. as a dietary supplement ingredient for many years.
Regulatory Background
Dietary supplements are principally regulated by the U.S. Food and Drug Administration under the Federal Food, Drug & Cosmetic Act (FDCA), which was amended by the Dietary Supplement Health and Education Act (DSHEA) of 1994. DSHEA establishes the criteria under which substances may lawfully be marketed as dietary supplements and protects consumer access to safe products.
In 2020, the U.S. Food and Drug Administration (FDA) took the position in warning letters that NAC is excluded from the definition of a dietary supplement because it had been previously approved as a new drug on Sept. 14, 1963. FDA said it was not aware of any evidence that the ingredient was marketed as a dietary supplement or as a food prior to that date.
This interpretation raised widespread concern across the natural products industry because it could have limited consumer access to NAC-containing supplements that had been lawfully marketed for decades.
NPA’s Advocacy on NAC
The Natural Products Association has taken a leadership role in advocating for the lawful market access of NAC as a dietary supplement ingredient. In 2021, NPA filed a citizen petition challenging FDA’s exclusion of NAC from the definition of a dietary supplement and alternatively requesting the agency undertake rulemaking to keep the ingredient on the market.
NPA’s petition and advocacy efforts emphasized the longstanding market history of NAC products and sought clarity on the proper application of the drug preclusion clause in DSHEA.
On Aug. 1, 2022, FDA issued final guidance advising companies of its intent to exercise enforcement discretion regarding the sale and distribution of certain products that contain NAC and are labeled as dietary supplements. This means that NAC-containing products labeled as dietary supplements may continue to be marketed in the U.S. for the time being, provided they comply with applicable requirements.
FDA’s guidance was published after NPA filed a citizen petition and a related lawsuit against FDA in Federal District Court. While FDA’s guidance was a positive development, NPA continues to press for permanent regulatory clarity through rulemaking and legislation to protect consumer access and industry innovation.
NPA had requested rulemaking as an alternative form of relief in its NAC citizen petition, and FDA responded in March 2022 that it hadn’t yet reached a decision on NPA’s rulemaking request. However, FDA is presently pursuing a rulemaking for NAC, according to NPA’s sources and the Trump administration’s Spring 2025 Unified Agenda of Regulatory and Deregulatory Actions.
A rulemaking would mark the first time that FDA has exercised its authority under section 201(ff)(3)(B) of the FDCA to provide by regulation that an ingredient (NAC) is not excluded from the definition of a dietary supplement. This would set an important precedent, giving the industry a roadmap to petition FDA for additional rulemakings to permit other ingredients in supplements that had been previously studied or approved as new drugs.
Why NAC Matters
NAC plays an important biochemical role in human health:
- Antioxidant Support: NAC contributes to the synthesis of glutathione, one of the body’s most important antioxidants.
- Respiratory Function: NAC’s mucolytic properties help break up mucus, supporting airway clearance.
- Detoxification Pathways: Clinically, NAC is an established antidote for acetaminophen toxicity and supports liver detoxification.
Consumers and manufacturers value NAC as a supplement ingredient, and ongoing scientific inquiry continues to evolve our understanding of its potential applications.
Protecting Consumer Access
For decades, NAC-containing products have provided consumers with choices in respiratory wellness, antioxidant support and general health applications. NPA’s advocacy is rooted in the principle that lawful dietary supplement ingredients should remain accessible to consumers when backed by appropriate evidence and marketed responsibly under DSHEA.
NPA has actively engaged with:
- Regulators to clarify and improve FDA policies and statutory provisions affecting NAC and other ingredients.
- Congressional offices to raise awareness about the importance of preserving consumer access to safe dietary supplements.
- Industry stakeholders to coordinate advocacy, education and compliance strategies.
Consumers and industry members alike can contact NPA to stay informed about NAC policy developments and how they may impact marketing, labeling and product innovation.
NAC Timeline
July 29, 2020: FDA announces issuing warning letters to seven companies whose products claim to cure, treat, mitigate, or prevent hangovers. In several letters, FDA concludes that NAC products are excluded from the definition of a dietary supplement under section 201(ff)(3)(B)(i) of the FDCA.
August 18, 2021: The Natural Products Association files a citizen petition with FDA, requesting that FDA either determine NAC is not excluded from the definition of a dietary supplement or, in the alternative, recommend that the Health and Human Services Secretary issue a regulation and find that NAC would be lawful in supplements.
Dec. 6, 2021: NPA files a lawsuit against FDA and HHS in the U.S. District Court of the District of Maryland. The complaint requests a judgment that the drug preclusion clause in DSHEA does not retroactively apply to the dietary supplement NAC.
March 31, 2022: FDA denies request in two citizen petitions asking the agency to determine that products containing NAC are not excluded from the definition of a dietary supplement. However, FDA says it has not reached a decision on NPA’s alternative request that the agency undertake rulemaking.
April 21, 2022: FDA announces availability of draft guidance on its policy regarding products labeled as dietary supplements and containing NAC.
August 1, 2022: FDA releases final guidance on NAC policy, announcing intent to exercise enforcement discretion. The guidance paves the way for companies to continue to sell NAC-containing supplements and for the world’s largest e-commerce platform (Amazon) to resume sales of these products.
2025: An FDA proposed rule, if finalized, would find that a specific ingredient (NAC) would not be excluded from the dietary supplement definition. As of December 2025, a notice of proposed rulemaking had not been published.
Key Press Coverage
NPA NAC Citizen Petition
Coverage from 2021 highlighted NPA’s citizen petition to FDA, which requested rulemaking or a determination that NAC isn’t excluded from the dietary supplement definition, with support from industry allies and congressional input from a U.S. senator. SupplySide Supplement Journal
NPA Lawsuit & Legal Action
- NPA sues FDA for trying to ban NAC supplements, warning that FDA’s actions set a dangerous precedent for dietary supplements after the agency retroactively applied the drug preclusion clause. Nutritional Outlook
- NPA in early 2022 files amended complaint against FDA, challenging its position on NAC’s legality in supplements. SupplySide Supplement Journal
- FDA gets reprieve from NPA lawsuit. NPA voluntarily dismissed its 2021 complaint against FDA in 2022 but preserved the ability to revive claims if future conflicts arise. SupplySide Supplement Journal
- NAC supplements dispute raises crucial question over drug research. Coverage highlighted NPA’s arguments and evidence that NAC had been marketed before DSHEA, contributing to industry pushback and legal discussion. SupplySide Supplement Journal
Market Impact & Enforcement
- Amazon resumes sales of NAC supplements after FDA published final guidance on its enforcement discretion for NAC-containing products. The outcome was tied to NPA’s advocacy and regulatory engagement. NutraIngredients
- FDA publishes final guidance on NAC, announcing its intent to exercise enforcement discretion. The news report highlighted the agency’s new policy, which permitted the continued sale of NAC products under certain conditions. Nutritional Outlook
Congressional Eyes
U.S. lawmaker presses FDA in new letter on NAC. The coverage focused on congressional inquiries, which was spurred by industry concerns, including NPA’s advocacy. SupplySide Supplement Journal
