Hi--

For what it is worth, the Japanese Wikipedia mentions the phyllo-
dulcin, but does not report health concerns about drinking this tea.

Amacha, in Japanese, is literally sweet (ama) tea (cha).

I suspect the concern is about the highly concentrated phyllo-dulcin
extract rather than the amacha itself. Also, it does not seem that
this is a wildly popular drink in Japan. I lived in Japan for 6
years, but never heard of it except for its ritual use in bathing
statues of the just-born historical Buddha in April. There are
apparently certain regions where people drink it regularly, though
this would certainly be a small population.

For anybody who was confused (as I was), "hortensia" is another name
for what I have always called "hydrangea."

james-henry holland