These experiments used a small dose - 1/6 to 1/8 what others have used. And, were performed in healthy mice that likely had normal NAD+ levels. So we don’t know how much different the results would be with older, sicker, mice and larger dosages.
As hebbeh notes -they did find that most Oral NR and NMN was degraded to NAM before reaching the bloodstream, whereas Injection was much more effective at delivering NR and NMN direct to bloodstream and on to NAD+
So I’d agree with others that does seem a vote for sublingual NR/NMN.
It does seem NR was more effective at reaching muscle, but I don’t see any other major differences.
One thing they did point out that hasn’t been mentioned is, they believe their results suggest NAD and possible NMN do cross the cell membrane in some tissues, and a transporter for NMN and NAD await discovery:
"Importantly, our findings do not exclude the possibility that NMN import and synthesis via NMNAT3 also contribute to the mitochondrial NAD pool. Indeed, Cambronne et al. recently employed a fluorescent biosensor to demonstrate that mitochondrial NAD levels are sensitive to depletion of either NMNAT3 (mitochondrial) or NMNAT2 (Golgi/cytosolic), implying that both NMN and NAD import contribute to the mitochondrial NAD pool.
This observation suggests that a mitochondrial transporter for NMN may also await discovery.
In summary, we show that mammalian mitochondria are capable of directly importing NAD.
This finding strongly suggests the existence of an undiscovered transporter in mammalian mitochondria "
Edited by able, 21 March 2018 - 04:50 AM.