Table 2. Health benefits of probiotic bacteria and their proposed mechanisms.

Health benefits	Proposed mechanism
Resistance to enteric pathogens	Antagonism
	Increased antibody production
	Colonization resistance
	Limiting access of enteric pathogens (pH, bacteriocins, antimicrobial peptides, lactic acid production)
Aid in lactose metabolism	Bacterial lactase hydrolyzes lactose in the small intestine
Small bowel bacterial overgrowth	Decrease toxic metabolite production
	Normalize small bowel flora
	Antibacterial characteristics
Immune system modulation	Strengthening of non-specific and antigen-specific defense
	Regulate/influence Th1/Th2 cell activation
	Production of anti-inflammatory cytokines
Anticolon cancer effect	Antimutagenic and anticarcinogenic activity
	Detoxification of carcinogenic metabolites
	Stimulation of immune function
Decreased detoxification/excretion of toxic microbial metabolites	Increased bifidobacterial cell counts and shift from a preferable protein-to carbohydrate-metabolizing microbial community
Anti-Allergic activity (eczema or atopic dermatitis, asthma)	Prevention of antigen translocation into blood stream
	Prevent excessive immunologic responses to increased amount of antigen
Blood lipids, heart disease	Assimilation of cholestrol by bacterial cell
	Alteration in the activity of bile salt hydrolase (BSH)
Urogenital infections	Adhesion to urinary and vaginal tract cells
	Competitive exclusion
Necrotizing enterocolitis	Decrease in TLRs and signaling molecules and increase in negative regulations
	Reduction in IL-8 response
Rotavirus gastroenteritis	Increased IgA response to the virus
Inflammatory bowel disease	Enhancement of mucosal barrier function
Crohn disease	Reduction in proinflammatory cytokines production

Adapted from Nagpal et al.²³