The Collaborative International Dictionary of English v.0.48:

Nutritious \Nu*tri"tious\, a. [L. nutricius, nutritius, from
   nutrix, -icis, a nurse, nutrire to nourish. See Nurse,
   Nourish.]
   Nourishing; promoting growth, or preventing decay; alimental.
   -- Nu*tri"tious*ly, adv. -- Nu*tri"tious*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nutritiousness
    n 1: the quality of being nourishing and promoting healthy
         growth [syn: nutritiousness, nutritiveness]