One word answer: hallucenations.
Complex answer: dwarves experience devistating mental infirmities from failure to consume alcohol, as they have evolved in such a fashion to actually metabolize the high energy liquid directly inside their brains, and it is this mechanism which sets them apart from the other sentient races, as well as being the source of inspiration for their so called "moods". Without this high energy dwarf fuel, dwarves experience a state similar to what humans experience when placed inside a sensory deprivation tank, and promptly begin to experience auditory, visual, and olfactory hallucenations, which is downright crippling to their ability to function. If this persists long enough, the hallucenations take on a coherent theme in most sufferers, centering around the wish fulfillment of drinking. This is the mind's last ditch effort to preserve itself in the face of being so impoverished. In this last final stage of systemic and complex hallucenation, dwarves will initiate a party, wherein all attending will honestly belive that there really is alcohol and food being served. The energy they exert while under this deception will exceed the energy stores remaining in their bodies, and promptly results in their deaths.
The providence of alcohol and food at this late stage might not always succeed in freeing them from death's clutches however, so experiments concerning the protracted effects of sobriety on dwarven populations are met with severe ethical disdain, regardless of how valuable suc data would be to the medical profession. As such, there is little to distinguish hard objective information from purely subjective folk tales and second hand rumor.
Is there really such a place as a truly impossible embark?