NMN is currently in legal limbo in the U.S., and most retailers have pulled NMN products from their shelves.
The path from NMN being legal for sale as a dietary supplement to effectively banned for supplement sales has several twists and turns. In 2018, NMN was granted GRAS (Generally Regarded As Safe) status by an FDA panel in 2018, which made it legal for use as a food additive. GRAS designation doesn’t apply to supplements, however—only food or food additives. For a product to be marketed and sold as a supplement, manufacturers need to submit a notification of a “New Dietary Ingredient” (NDI) to the FDA, before bringing the product to the market. NDI's contain information providing the basis for concluding that the supplement is reasonably safe and, if approved by the FDA, pave the way for sales and marketing as a supplement.
One company did successfully get an NDI approved by the FDA for NMN supplements in 2022, which gave NMN the appropriate legal status for supplement sales. However, later the same year, the FDA changed their stance on NMN’s status as a dietary supplement. Several companies that were testing NMN in clinical trials successfully lobbied the FDA to have NMN classified as an investigational drug. This effectively made NMN supplement sales illegal according to 21 U.S.C. § 321(ff) (section 201(ff) of the Federal Food, Drug, and Cosmetic Act, which prevents the sales or marketing of agents classified as investigational drugs.
This prompted the FDA to revoke the NDI, which effectively banned the sales and marketing of NMN supplements in the US. Technically, selling NMN as a food additive is still legal, since NMN’s GRAS status was not affected by the withdrawal of the NDI. Nonetheless, most retailers stopped selling NMN products considering its uncertain legal status.