Vitamin A is necessary for maintenance and repair of skin and mucous membranes. Vitamin A is important for oral health (teeth, gums). Bad oral condition is a environment for bad breath.
A deficiency of B vitamins may be the cause of bad breath and body odor. A daily dose of B3 with each meal, and 50 mg of B6 could help with the halitosis and digestive trouble. Also a combination of vitamin B complex and magnesium will reduce certain secretions that can cause odor.
Lack of vitamin C could lead to scurvy, a disease recognizable by the destruction of the of the gums. The destruction of oral tissues sets up the perfect environment for the proliferation of odor causing bacteria.