The agency is doubling down on its position that nicotinamide mononucleotide (NMN) is not a legal supplement. Action Alert! In a letter recently made public on the federal docket, the FDA has restated the position it announced in October 2022 that NMN does not meet the definition of a dietary supplement because, in the agency’s view, it was studied as a drug before it was ever sold in or as a supplement. Read more.