why might consuming more of daily rni of a vitamin or mineral be harmful

1 answer

http://healthyeating.sfgate.com/can-taking-much-vitamin-b12-harmful-7189.html

http://healthyeating.sfgate.com/can-much-vitamin-b6-vitamin-b12-6060.html

http://www.drweil.com/drw/u/ART02810/facts-about-vitamin-b