Dr. Kellogg wrote something like fifty books, famously dictating at least some of the copy while riding his bicycle round and round in circles (his stenographer had to get up early and hustle over to the Doctor's house where he sat on a stool in the middle of a paved circle so as to be ready for Kellogg's early morning exercise session). Are they the "final word" on all things medical? I don't think so. CPR hadn't been invented, for instance, but I wouldn't want to ignore it just because Kellogg didn't put it in his books.
Still, there's a lot to be gained there. And some to be avoided, of course, like Living Temple, for instance. I've never read the book. Don't plan on reading it. Why should I, when God called it deceptive and dangerous? That said, if the four or five paragraphs that everyone quotes from the book is the most blatant pantheism to be found there, I'm pretty sure I could find worse in just about any library or health food store book section. I don't read them, either.