Using the same cytotoxicity measurement method, the research team then sought to determine whether similar benefits come from administering NMN orally. In the 32-week-old mice Takeda and Okumura used for their analysis, 625 mg/kg of orally-supplemented NMN significantly enhanced NK cell cytotoxicity. Neither injecting or orally dosing NMN increased the NK cell numbers. This result strongly supports that NMN supplementation improves overall NK cell cytotoxicity in mice, because NK cells show improved, potent cancer cell-destroying abilities without becoming more abundant.
Studies continue to show the translatability of NMN’s health benefits from mice to humans in conditions like reduced insulin sensitivity, running endurance, and aged muscle function. So, although how and whether these results apply to humans remain up in the air, the study offers hope for the tantalizing prospect that NMN improves aged human immunity through improved NK cell cytotoxicity.
Some study limitations include that NMN boosts NK cell cytotoxicity optimally at different ratios of NK cells to cancer cells, but the significance of this finding wasn’t explored. For example, the optimal proportion of NK cells to cancer cells with oral dosages is 10 to 20 in the liver but 200 in the spleen. The precise meaning of this finding remains uncertain.
Another limitation is that the cytotoxicity analyses were done in laboratory dishes, which don’t always translate to live tissue. Future experiments can utilize cytotoxicity measurements in live animal tissues to further support that NMN boosts NK cell cytotoxicity.