What is the conversation mainly about?

W: Gosh! Kevin, are you OK? Another cup of coffee?
M: Yeah, I stayed up all night cramming for my poetry exam. I couldn’t keep my eyes open in my last class. I’m having this coffee so I can stay awake this afternoon.
W: Haven’t you ever heard that drinking too much coffee is harmful to your health?
M: It’s a little odd. What do you mean harmful?
W: Well, for one thing it may cause heart disease.
M: Most of the research about the link between coffee and heart disease is inconclusive.
W: But coffee has caffeine that is addictive, once addicted, it’s hard to kick it off.
M: Not so horrible. You can’t become addicted to caffeine like other drugs.
W: Yes, you can. Don’t you know that people who are deprived of caffeine suffer with draw symptoms, especially headache?
M: Oddly enough, one cure for headache is caffeine. Besides, coffee helps me work faster?
W: Studies have showed that coffee makes you work faster but not necessarily better. You may finish your exam in a shorter period but you won’t have fewer errors.
M: You know, soda in your drink has caffeine too.
W: But 12 ounces of soda has half the caffeine of a 5 ounces cup of coffee. And a cup of tea has less than that.
M: But I cannot resist the taste of coffee.
W: You could drink decal Decaffeinated coffee doesn’t have as much flavor or body as regular coffee.