NAD+ Forums

Instability in NAD+metabolism leads to impaired cardiac mitochondrial function and communication
"...In addition, we show that myocardial mtDNA damage in combination with high dosages of nicotinamide riboside (NR) causes inhibition of sirtuin activity due to accumulation of nicotinamide (NAM), in addition to irregular cardiac mitochondrial morphology. Consequently, high doses of NR should be used with caution, especially when cardiomyopathic symptoms are caused by mitochondrial dysfunction and instability of mtDNA."

https://elifesciences.org/articles/59828
(Open Access)

It seems like they're talking about massive amounts of NR here, as far as I can tell Well over 5 grams, maybe closer to 10 grams really. Definitely good to keep in mind for anyone thinking "more is always better". Here is very specific evidence that it's not. 

Exactly and agreed, More is not always better and I think if you keep the NR at a gram a day you should be fine. I also think you should add some TMG to the mix if doing just NR for a NAD booster.