You can search by keyword, illness category or disease. This is all part of a commercial physician information web site called Dynamed which requires prior registration. Although guest registration is currently free, from 1998 use of the full information data base will be fee based. FDA search Search the FDA's web server for nutrition documents. Search individual CDC data bases, but no overall search engine.
None are specifically nutritional.
Also list of health links. This page has search engines for school meals-related data bases, information about the national program. There is also a gopher site . German agric.science literature search German agricultural science literature data bank search engine. Search engine with simple Boolean terms.