My hunch was based on these strands of knowledge:
The Nature Boys of the 40's - 60's, who built many of the first California health food stores and were influential in counterculture, alternative medicine, and especially H-A hippie culture, were themselves descended from the early 20th C German youth movements. While these movements were characterised by hiking, camping, healthy living, and self-reliance, this was closely tied to ideas of German superiority and return to Teutonic ideals. They read Hesse and Nietzsche, listened to Wagner, and stressed personal will. Many were quite specific in their return to German pagan roots. (The relation of this to later Nazi developments are not inevitable, but pretty clear.)
The American versions of this all-natural approach came from the Midwest, especially upper Midwest, which were largely German, Dutch, and Scandinavian settled.
The earliest naturopathic, homeopathic, and related alt-medicine practices came a century before that from other Germanic sources, from a philosophical ferment which focused on life-force, and gods from nature. Though of course, that last is hardly unusual, as most cultures drew their gods and goddesses from what we would today generally call "nature."
I also had a vague idea that the Puritan strain of reading from the Book of Nature as well as the Bible, and the relation of that both to earlier Germanic outlook and later Unitarian beliefs, seemed to suggest a continuity from those Teutonic thoughts to modern nature-emphasisers and Gaian thinking. Even then I thought it was tenuous, but something might be made of it.
My hunch prover to be more correct than not, but I got some things wrong. For example, I thought I would get to ruin the song "The Happy Wanderer" for you, as it seemed clearly tied to the late 19th C Wandervogel movement of strong young Germans hiking, breathing fresh air, eating vegetables, and enduring hardships. And where that led. German evangelicals* were especially big on this, which was one of their reasons for supporting Hitler in his first few years. We have always fallen for movements that get the teenagers to be polite and get focused, I'm afraid. They got off than bandwagon, but a lot of the damage had already been done.
But the song has only the most distant connections to such things, having been written in 1954. I'm not going to hold hiking in general against the Germans. The craze had always been British and American as well, and now everyone is getting into the act.
In my research on the song, however, I came across this, which illustrates that the Germans are still not quite like us. They were not known as stern and emotionless until the mid-20th C. They were regarded as hopeless oversentimental romantics (see Literature, German, 18th-19th C) who might burst into tears at old songs or go off and believe anything. Perhaps that gives us a better understanding of why they went insane.
Details to follow.
*Evangelical had somewhat different meaning in that culture, as it primarily meant Lutherans and Calvinist groups.
