Peter Bowes' Live Long and Master Aging podcast Episode 53 features an interview with the University of Iowa's Dr. Charles Brenner, the scientist who discovered that NR replenishes NAD in humans. Here is an excerpt:
"We discovered Nicotinamide Riboside -- a third vitamin precursor of NAD -- and we also discovered the NR Kinase pathway -- a fourth way that yeast cells and human beings can make NAD.
"So there's an amino acid, tryptophan, that can be converted to NAD. And there's two classical forms of Vitamin b3 -- called nicotinamide and nicotinic acid -- which we have known since 1938 are NAD precursor vitamins.
"And in 2004 we showed that NR -- nicotinamide riboside -- is a third vitamin precursor of NAD. It has a unique biosynthetic pathway.
"And it's a particularly valuable form of vitamin B3 -- it's not identical to the other forms -- because the NR Kinase pathway is on in every single cell and tissue in the human body, whereas the ability to make NAD from tryptophan or nicotinamide is tissue-specific; it doesn't work in every single tissue.
"High-dose nicotinic acid causes a flush reaction, flushing, in which your face gets hot and red. High-dose nicotinamide actually inhibits sirtuins, these enzymes that play a role in longevity.
"Many cells that are diseased or stressed are turning down the ability to convert nicotinamide to NAD, whereas many cells that are diseased or stressed are turning UP the NR Kinase pathway.
"And we have shown recently that in heart failure and neural protection, the NR Kinase pathway -- the genes -- are turned on -- and that's why NR is a specifically valuable form of Vitamin B3 to boost NAD in times of stress..."
The interview is HIGHLY recommended, and goes on to consider the evidence that boosting NAD via NR can prevent numerous forms of neuropathy, and discusses how NR helps people retain their capabilities, and stay more active and more resilient as they age -- as well as Dr. Brenner's personal experiences as the first person to ever take NR. (NR is sold by ChromaDex under the brand Tru Niagen).