I mean in real life it's definitely the result of being poisoned by consuming the byproduct of rotting fruit. Humans are just so dumb and determined that we just decide warning signs not to consume things mean they're awesome.
See also hot peppers and hallucinagenics (sp?).
Sure, what I'm sayin is that it's arguable whether a thing we consume that causes effects on the body and mind is necessarily a
poison. I think it's an overbroad definition of the term, that causes my welbutrin to count as a poison. In general, when a definition causes a common thing to be defined in a way that feels completely wrong on a colloquial level, the definition has gotten off track.
Tumeric may have some harmful properties to some creatures, but it isn't a poison for humans, and is generally fairly beneficial (though it's healing properties are much overblown by so-called naturalists and herbal remedy salesfolks). Still, a spice whose primary purpose in nature is to make a creature sick when encountered, I'm fine with defining it as a poison in that context, but alcohol doesn't fit that. Inebriation isn't even a negative effect unless it is extreme, and light alcohol inebriation has both recreational and situationally practical benefits, and alcohol itself is a very common part of medicine. Not to mention the non-consumption uses of alcohol.
What's more, there are fruits and other foods that aren't harmful at all to humans but will kill other animals, even other mammals, and even some which are harmless to some humans but lethal to others. Not all of them are even dangerous to the creatures they're dangerous to as a defense mechanism, a lot of it is just random traits appearing in the billions of species that have spawned and developed over the eons.
Anyway this is a tangent. There is a lot to mine in the realm of substances that effect humans strongly that might not do so for dwarves, and perhaps stuff that goes the other way.
For instance, if dwarves digest and gain nutritional value from things like moss and lichen and perhaps even fiber, what does that mean in terms of how easy it is for a dwarf to overeat, and in terms of how much
energy they get from their food? When a dwarf drinks bear, are they
eating from a nutritional standpoint? If so, does that mean that they
really need to work those calories off in order to stay healthy, and have a natural instinctive imperitive to physically exert themselves that takes rather a lot of work from a human perspective to get out of their system?
Just how many hours a week does a wealthy dwarf spend in the gym? Just how good at marathons are dwarves? Would it be appropriate to give them some sort of benefit against exhaustion or when spending hit dice? That could help keep them vigorous and tough in spite of +2 con becoming optional.