I take a men's multi-vitamin because I don't eat much for veggies beyond potatoes, corn and carrots. I eat a lot of beef and pork. I don't watch my salt or fat intake (though I do watch my sugar intake because I'm Type II diabetic).
I just had bloodwork done, and other than my sugars not "under control" I'm very healthy. Cholesterol is excellent as is my blood pressure.
In any case, as long as it's reputable (IE not from China and filled with lead and melamine) and you follow the directions, it can't hurt.