I just researched it, it's actually worse, the GI of maltodextrin is like 105-130, that's higher than plain sugar or dextrose.
I didn't know that... thanks, I've actually switched my subscription to Biolent, the carbs in it come from oat and buckwheat flour, it has more fibers and no fast carbs as far as I can tell. I'm Canadian so it's only slightly more expensive for me.
Apparently, I got the high/low backwards, but keep in mind the GI of a serving of Soylent is 60 for the powder, 49 for the drink. You can't just take the index of one ingredient alone and peg the whole product to that when the other ingredients influence absorption. Soylent's glycemic load over time is pretty modest.
