This article talks about alcohol induced changes in your gut flora, and how it can cause bad bacteria to overgrow. This could lead to vitamin deficiencies like what you're describing...good luck
"A significant alteration of colonic microbiota (dysbiosis) was found in alcohol-fed rats with respect to dextrose-fed rats. Moreover alcohol-induced colonic dysbiosis was prevented by the administration of lactobacillus GG or oats."