What it is
The pressed sap of the yacon tuber, mostly fructooligosaccharides — sugar chains your enzymes can't cut. Marketed as a prebiotic, low-glycemic weight-loss syrup.
Why your biology objects
The FOS passes undigested to the colon and feeds bifidobacteria (glycemic index near 1) — a genuine prebiotic with a small human trial behind it. Dose-bound the honest way: above ~15–20g a day it reliably causes gas, bloating and loose stools. Tuber-derived and whole-ish.