As much as 90% of Halitosis is caused by bacterial by-product which is related to low saliva flow (dry mouth), active gum disease, tooth decays and ill-fitted dentures.
10% of halitosis comes from underlying stomach problems.
Regular professional teeth scale and clean by dentists followed by oral hygiene instruction can reduce active gum disease.
Remember to brush you tongue where bacteria like to harbour overnight and use mouth rinse if needed. Cavities retaining bacteria and food will need to be restored with fillings.
Having bad breath can give others a bad impression when you talk to people at a short distance.