persistently slightly elevated ALT

I have had numerous blood tests done in the past 6 months (5) for various health insurance inquiries (life, disability, and a "prevention plan" for my group insurer) and I have followed up with my doctor twice due to the results.  In each test everything was normal (all liver function tests, kidney, cholesterol, and glucose) except in each test my ALT liver enzyme has been slightly elevated (72, 52, 62, 64, and 68, respectfully).  I am a 26 years old male and I am not overweight, I excercise regularly, and I am displaying no symptoms of anything.  As far as I can tell I am completely healthy.  My doctor has reassured me that this slightly elevated liver enzyme is nothing to worry about, and that we should maybe just keep an eye on it.  But, it remains in the back of my mind.  I do drink alcohol a little more than I should (probably 15-20 drinks per week, always beer).  I am not on any medication and I never have been. I don't know if it's relevant, but I think I may have a minor case of IBS because I sometimes get stomach aches that are relieved by bowel movements (1 every two weeks or so).  

[nd102]

As a follow up. I have tested negative for hepatitis b and c twice (6 months apart). I also urinate frequently, but I think that is likely attributable to the fact that I drink 10+ glasses of water a day and drink coffee and soda all day.  I regularly have 2-4 bowel movements a day that seem to increase if I eat a high fat meal.  Also before my last blood test I abstained from all alcohol for 3 weeks beforehand and my alt remained slightly elevated (68).  What questions should I ask my doctor and what steps should I take other than just taking a blood test every six months, if any.  Thanks in advance.

[B_Shel20]

The alcohol consumption can EASILY affect the ALT levels. So can things like lifting weights and taking pain meds like Aspirin.

Your levels are minimally elevated, and could easily be affected by the drinking or any of the other following factors.