Nancy,
The requirement for niacin (also called Vitamin B3) for us seems to be 100% of the RDA, which is 16mg a day for men, 14mg a day for women. Here's a really good article on it from the University of Maryland Medical Center:
http://www.umm.edu/altmed/ConsSupple...3Niacincs.html
If you're more interested in optimum daily intake, rather than the recommended daily allowance (which may not be valid for us, due to the malabsorption issues), go to
http://bariatricsupermarket.com/vitamins.html for a good article. Just as a warning, though, I always mistrust articles found on sites that are selling something. Especially when they're telling me that I need to supplement up to ten times the government's recommended amount, and they just happen to sell that supplement.
For new GBS moms-to-be, a terrific article on vitamins for breastfeeding post-GBS moms:
http://www.todaysdietitian.com/newar...2006pg47.shtml