Was Martin Van Vuren a heavy drinker? The site Medical History of American Presidents reports, "By age 25 van Buren had a reputation for being able to drink large quantities of alcohol without showing signs of drunkenness. As a result, his nickname was "Blue Whiskey Van." His heavy drinking seems to have persisted even into the Vice Presidency (1833-1837)."
I have searched the Web for this and could only find three hits on the phrase "Blue Whiskey Van." The site above references The Health of the Presidents: The 41 United States Presidents Through 1993 from a Physician's Point of View by John R. Bumgarner for this fact. As I do not have access to this book, I'll have to try and search around some more.
Of course, being a heavy drinker was not considered a bad thing by most people in the 19th century. The water was bad and could kill you. Alcohol was a safe choice. Van Buren made it to his late 70s as well which was pretty good for his time so the drinking did not harm him too much.
I'll be keeping my eye out for more on this "Blue Whiskey Van" nickname. If anyone else knows of good sources, please drop me a comment. I expect that I'll find a treasure trove of references to this in 6 months to a year from now from a visitor who finds this post via a search engine search on this phrase.