On Monday, the U.S. Food and Drug Administration (FDA or the Agency) responded to a citizen petition about beta nicotinamide mononucleotide (NMN), signaling a shift in its regulatory approach that brings both opportunities and challenges for dietary supplement companies. In two letters dated September 29, 2025, the FDA confirmed that NMN is not excluded from the definition of a dietary supplement, reversing its previous position that had excluded NMN products from the market.
FDA's New Position Opens the Door for NMN Products
FDA's reversal centers on its analysis of the "race to market" provision under federal law, which determines whether a substance can be sold as a dietary supplement if it is also being investigated as a drug. The Agency concluded that there is enough evidence showing NMN was marketed as a dietary supplement in the United States before it was authorized for drug investigation, allowing it to remain available as a supplement ingredient. FDA clarified that it does not require proof that the ingredient was lawfully marketed or otherwise compliant with all laws and regulations, only that the marketing occurred in the United States before the critical drug authorization date.
Critical Compliance Requirements Remain in Place
While this decision removes the categorical ban, it does not eliminate regulatory hurdles. NMN remains classified as a New Dietary Ingredient (NDI), meaning companies must still satisfy premarket notification requirements before marketing NMN products. Each company marketing NMN must submit a New Dietary Ingredient Notification (NDIN) to the FDA unless the ingredient is sourced from the same supplier/manufacturer that previously filed an NDIN. Moreover, companies cannot rely on self-affirmed GRAS status to bypass NDIN requirements, and products lacking proper NDIN submissions remain subject to adulteration claims and enforcement action.
Significant Legal and Business Risks Persist
Despite the FDA's favorable determination, substantial risks remain that could impact business operations and legal exposure. The Supreme Court's recent Loper Bright decision eliminated judicial deference to Agency interpretations, meaning courts may now scrutinize the FDA's position more closely in any legal challenges. This creates uncertainty about whether the FDA's current interpretation will survive judicial review, particularly given that the courts may presume the law requires it to have been lawfully marketed to avoid the preclusion provision—a standard that could conflict with the FDA's analysis.
Moreover, the regulatory landscape faces increased uncertainty from potential policy shifts under future administrations, as this determination reflects only the FDA's current thinking and could be reconsidered or reversed. More immediately, plaintiff attorneys may use California's Unfair Competition Law to challenge NMN products as unlawful, arguing that the FDA's decision conflicts with statutory requirements or that the Agency's interpretation is legally flawed.
Strategic Implications for Your Business
FDA did not issue interpretive guidance providing clear criteria relating to drug exclusion exceptions. Importantly, the FDA did not issue guidance concerning what constitutes "Substantial Investigations." Rather, the Agency noted its guidance development process depends on various factors, including the need to preserve the Agency's limited resources for "priority matters." Consequently, it does not appear that the FDA will consider resolving the regulatory ambiguity between certain pharmaceuticals and dietary supplements in the near future.
Companies marketing or considering NMN products face complex compliance and risk management decisions that require careful legal analysis. The intersection of NDIN requirements, potential litigation exposure, and regulatory uncertainty creates a challenging environment where seemingly compliant products could still face significant legal challenges. Understanding how these risk factors apply to your products, supply chains, and target markets is essential for making informed business decisions.
The evolving regulatory and legal landscape surrounding NMN presents both opportunities to enter or expand in this market and risks that could result in costly enforcement actions or private litigation. Companies require tailored strategies that address their unique circumstances while anticipating potential shifts in the FDA's stance and the broader legal landscape.
Please contact the authors with any questions.