The books say that the trolls are silicon-based lifeforms (ie stone), made of metamorphorical rock. I can't remember which book says it, but they used to try eating humans in the past even though they couldn't digest them. They just did it for fun, I guess. Everything we see a troll consume is mineral-based (hence the joke about Detritus's drink in the Bucket, "one molten sulphur on coke with phosphoric acid ", which is a pun on 'coke' referencing the fact that Coca Cola actually contains phosphoric acid). So troll food, drink and drugs should not be digestible to humans and dwarfs - but there's a chance they could be poisonous.

Mrs G
The Garner who cares.