What can be a possible reason for & solution to bad breath if it persists inspite of regular brushing?

bad breath
Drizn asked:

one of my family members had a tooth problem few years back. However now he is very particular about regular brushing after meals, using mouthwashes etc. I dont find anything wrong with his eating habits as well but he does have stomach problems at times. Inspite of his discipline, his breath starts smelling after sometime of brushing. Please suggest what is the reason for it & what can be done to solve this problem.

Bad breath Gone