what does the Torah, Talmud and other scriptures (commentators) say about alternative treatments and medicines (yoga, accupuncture, ayurveda, haptonomy etc.)? Is it ok to get this kind of healthcare? At what point do medicines or treatments become 'not allowed' or 'allowed' acording to scriptures?
Many have spoken up and warned against healing methods based upon non-Jewish, eastern style mysticism, that are not proven on a scientific basis, but often are based on idolatrious practices (like yoga).
You can read such a warning from Rabbi Yitzchak Ginsburgh:
Here you have a similar summary from various dati leumi rabbis:
Here is a general summary about alternative healing practices, mostly emphasizing the importance of not relying on them exclusively (it doesn't mention yoga and the like, probably because it was written earlier when it was not that prevalent):
If you have some time, I think it worth very much to listen to this shiur about the general understanding of the mitzvah tamim tihye, not looking for any "esoteric" kind of things. It gives a very healthy general approach to a lot of other issues as well, and it is mostly excerpted from a book of Rabbi Yaakov Hillel:
And let me add my 5 cents to the issue at the end: I am somewhat surprised, why the incident mentioned at the end of Avodah Zarah 27b is not referenced in sources which are discussing this issue. I think it presents a very important reason why to avoid cures which are rooted in not so clear sources:
Rabbi Yishmael didn't let a min to cure his nephew of a snakebite, and subsequently, the latter died of it. He was concerned that the nephew or the people surrounding would be influenced by the worldview of the one who healed him.
I think this line of reasoning is certainly applicable in our world, where there is such a big chaos of every kind of strange ideas!
In a recently published book from the writings of Rabbi Yisroel Belsky Z"L, titled "Shulchan HaLevi on Alternative Medicine", the exact workings and halachic ramifications of many such methods are clarified. The Psak is that all alternative medicines (including Energy and New Age healing) are absolutely forbidden.
Rabbi Tendler wrote in the name of his father-in-law (Reb Moshe Feinstein) that fake medicine leads to false beliefs, and Reb Moshe refused to answer whether such medicine was kosher or not.
However, Rabbi Meir Amsel wrote that this answer doesn't sound like something Reb Moshe would write, and he ruled that taking such medicines (when it's Pikuach Nefesh) is permitted even when it violates the Torah.