Seems like he was kind of right concerning muscle tissue... according to this (https://www.ncbi.nlm...51433/table/T1/)
And here are some quotes from "ChromaDex: Response To The Claim Niagen Is Just 'Expensive Vitamin B3" interview (https://seekingalpha...sive-vitamin-b3)
Q: The article I asked you to read stated that "All three produce NAD+ in the human body." Please elaborate on this.
Q: What's the problem with niacin or nicotinamide as a NAD+ precursor?
CB: There are trillions of cells in the human body of many hundreds of cell types. For example, there are nerve cells, skeletal muscle cells, cardiac cells, several types of pancreatic cells, several types of blood cells, liver cells, etc. What makes a neuron a neuron and not a hepatocyte is the expression of neuronal genes. When we discovered NR as a vitamin, we discovered the NR pathway to NAD. The value proposition of NR depends on the unique ability of NR to maintain and boost NAD in every cell and tissue and, in particular, in tissues undergoing damage and stress.
There are only two steps in the NR pathway to NAD but there are two genes that can do the first step and three genes that can do the second step. The NR pathway never gets turned off. NRK1 is expressed in every cell and tissue, while NRK2 is turned on by cellular damage, particularly in skeletal and cardiac muscle. This means that people supplementing with NR are able to keep NAD levels high in stressed cells that specifically have the NR pathway turned on to deal with cellular stress. Supplementing with niacin and nicotinamide doesn't help because they don't feed into the NR pathway, which is turned on by stresses.
CB: There are three problems with niacin and two problems with nicotinamide, particularly at high doses.
First, niacin can't be used in lots of tissues because the niacin pathway is not on. The brain and skeletal muscle can't use niacin to boost NAD and these are two of the most important tissues that suffer the ravages of aging. Niacin also causes flushing at high doses and does not efficiently elevate mitochondrial NAD.
The nicotinamide pathway declines in aging, which means you would need ever higher doses to try to maintain your NAD. Second, at high doses, nicotinamide inhibits sirtuins, which is the opposite of NR. NR is a STAC that extends lifespan in model systems.
To my understanding one essential point is that NR can boost NAD even in damaged/stressed cells. And NMN is even better at this task.
And i can remember some study graphics which showed different NAD+ levels by NA, NR and NMN, where NMN and NR NAD+ levels where way above NA. Unfortunately can't find it anymore.
I'm personally not sure what to think about all of that, at this point. Maybe, in the meanwhile, i just take NA, NR and NMN all together
Edited by Florian E., 16 April 2017 - 02:47 PM.