Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
healthy, healthful (adjs.)
Healthy means “having good health, traceable to good health,” as in He’s a healthy boy, and healthful means “salutary, conducive to good health,” as in She eats nothing but healthful foods. Much Edited English and some conservative practice tries to maintain those distinctions, but most Standard English now accepts healthy as readily substitutable for healthful, as in Milk is a healthy thing to drink. Healthy also is used in the sense of “vigorous, thriving, great,” as in I learned a healthy respect for his left hook; some argue that this sense is Colloquial, but there is considerable evidence that it is Standard.
