The FDA is reclassifying NMN because it is currently under substantial clinical investigation as a pharmaceutical drug, indicating its effectiveness. This move is influenced by Metro International Biotech's trials on NMN for drug development. According to the Dietary Supplement Health and Education Act (DSHEA), an ingredient cannot be marketed as a dietary supplement if it is also under investigation as a drug and these studies were publicized before it was marketed as a supplement. The FDA's decision aims to control NMN due to its promising benefits and effectiveness.