I have been researching the use of NR and the other NAD+ precursor, NMN, for a few months now. The only definitive studies that showed tissue absorption levels have been done on mice. Both NR and NMN were tagged with a radioactive marker so that they could be detected in the mouse tissue when absorbed.
The studies showed that NR and NMN that was orally ingested did not show significant uptake levels in body tissues like the liver, kidneys, or brain. Injecting the mice with the supplements did show up in their tissues, but only at dosage levels that were well above what would be considered safe for humans.
Amazon has recently banned the sale of NMN due to a large amount of fake products being marketed. If you want to biohack these the safest companies would be Tru Niagen and DoNotAge. DoNotAge is made in the UK and is a fraction of the cost of Tru Niagen.
Here’s a link to a video on the studies.
https://youtu.be/hggLOXhFRxc
The problem of poor absorption when taking oral capsules seems to be avoided by using the NMN powder under the tongue. It gets absorbed directly into the bloodstream and is not digested in the stomach. I’m looking at getting the NMN powder from DoNotAge.com. The 100g container is $117 or about 1.17/day. This is a 3-month+ supply. You can subscribe to get a 400g container (1+ year supply) for $400 or 1$/day which is the best price around for a certified safe and effective NMN supplement.
The NAD+ that I take is liposomal and includes a betaine for better absorption. No, I don’t have rigorous bio-assay proof of that.
“Amazon has recently banned the sale of NMN due to a large amount of fake products being marketed”
There appear to be “hundreds” of claimed NMN products for sale on Amazon right now.