They are clearly abusing heavy drinkers, which is the category with the highest consumption level [eg > 4-5/day ]. Alcoholism requires a psychological addiction added to the abuse, which may have occurred since they can't seem to stop.
I posted a wine and Health thing on alcoholism. Check the Search function. These definitions are based on standard aliquot of alcohol 1 2 oz shot=1 4 oz glass wine = 1 12 oz beer. Clearly they are broadly defined for the standard man, which I'm still trying to find.
Denial is an early symptom. Not everyone will have it. And it may not be manifest to you as a friend...but it might be to an inquiring doctor or a boss.
Lastly, do not be misled by "apparent good health." Too many have boasted that false claim. Cirrhosis is histologically defined but Childs- Pugh clinical staging systems exist as well. 90% of the liver is destroyed before enzyme elevation is persistent, so the body takes quite a bit of abuse before giving up. Think of alcoholics good health as false observation, sort of like the murderer next door analogy,
" well he seemed like a nice normal young man"
Last of all, I have three degrees. They hang on the wall and represent my minimum ticket to the party. But everyone who works and wishes to succeed and advance in their line of work following graduation must be a lifelong student