can someone help me please in my assignment I have to explain concepts of nutritional health. Many thanks.

Your post is quite vague, but perhaps you'll find some useful information in here:

http://www.google.com/search?q=concepts+of+nutritional+health&ie=utf-8&oe=utf-8&aq=t&client=firefox-a&rlz=1R1GGGL_en___US357