[rotwoof]

It is also possible to reduce the glycemic index of food by ingesting acetic acid (apple vinegar).

See: http://www.jbc.org/content/135/1/157.full.pdf

TL;DR Apple cider vinegar will decrease the glycemic index of food by interfering with carbohydrate digestion.

[cbr]

Acetic acid is vinegar, not apple cider vinegar in particular.