Here is some niacin/nicotinamide info for you.

Basically nicotinamide has less potential for causing the dreaded flushing(which for some is very uncomfortable)

However in very high doses nicotinamide shares toxicity warnings that
are attached to niacin also.
Here is a really good monograph from Linus Pauling Institute on both:
http://lpi.oregonstate.edu/infocente...cin/index.html

Long term niacin/nicotinamide should be monitored every 3 to 6 months with a liver test at the doctor's.

I skimmed the research and it is unclear to me how much you would need.
The toxicity listed at Linus Pauling Institute would be a guideline for you.

While it is true that the B vitamins are water soluble, and hence to not build up in the body, Niacin has other effects at high dosage.

This article also discusses NAD which is in the research articles posted here.

You can use NAD as a supplement... The NOW company makes it:
http://www.nowfoods.com/?cat_id=2822
The link above explains it.

I am sorry, I cannot advise you about doses to use.
There is a warning in one of the articles that very high doses would be needed for humans...and that would necessitate physician supervision. (we are talking in the gram range here). 500mg/day of nicotinamide is not essentially harmful, but it may be too low for your purposes here.

It is interesting none the less. I found an article in Science News, on MS, this week, using a new drug (actually an old drug recycled for this purpose).
I'll post that later today in a new thread.