I suppose the first question should really be, "What truth is there to this?"
On a related note, I've read that in Victorian England street vendors would cut coffee with ground acorn and carrot. Did England have better access to coffee that they could adulterate rather than substitute?
In world war one and two, there was a practice of using Ersatz(replacement) goods. one of these included coffee, which was instead made of roasted acorns or chicory (this is still used today as a coffee substitute). Source: /u/kieslowskifan has made a very in-depth post about this and you might find very interesting https://www.reddit.com/r/AskHistorians/comments/61q10r/during_ww2_how_did_germany_get_goods_like_coffee/dfh1ln1