I think there is some scientific data out there...that supports that too. But I don't know for sure...
There is a lot of scientific evidence that there is a connection between ancestry and alcoholism. There is a map of estimated years of life lost to alcohol abuse at:
http://en.wikipedia.org/wiki/File:Alcohol_use_disorders_world_map_-_DALY_-_WHO2002.svg
It clearly shows that the middle east enjoys the lowest incidence, and as one moves farther from there the incidence increases. Some scientists speculate this has to do with number of generations exposed to alcohol - that there is a natural selection process whereby, due to early death, alcohol abusers are gradually eliminated from the gene pool.
Native Americans apparently were not exposed to alcohol before Europeans arrived, and so the process of weeding-out those unable to handle alcohol is in its early stages.
So Native Americans have higher rates of alcohol abuse. But, like all human beings, they have free will to indulge or not. And the consequences should not be a surprise.
IOW, American Indians are prone to alcoholism...based on their innate inability to metabolize alcohol as others do. My own personal anecdotal evidence bears this out.
I think there are other studies...that are equally interesting...where carb's and fat's aren't metabolized the same way as white people...when studying diabetic Indians.
And diabetic Indians is a huge problem, as is alcoholism........
FWIW-