Table 1.

Differences between probiotics, synbiotics, prebiotics, and postbiotics.

Classification	Probiotics	Synbiotics	Prebiotics	Postbiotics
Definition	Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host	A mixture comprising live microorganisms and substrate(s) selectively utilized by host microorganisms that confers a health benefit on the host	A substrate that is selectively utilized by host microorganisms conferring a health benefit	Preparation of inanimate microorganisms and/or their components that confers a health benefit on the host
Category	Bifidobacterium (adolescentis, animalis, bifidum, breve and longum); Lactobacillus (acidophilus, casei, fermentum, gasseri, johnsonii, paracasei, plantarum, rhamnosus and salivarius)	Complementary (prebiotic + probiotic); Synergistic (live microorganism + substrate)	Conjugated linoleic acids and polyunsaturated fatty acids; Oligosaccharides; Human milk oligosaccharides; Phenolics and phytochemicals; Readily fermentable	Inactivated strain (such as Bacteroides xylanisolvens, Apilactobacillus kunkeei and Saccharomyces boulardii); Bacterial lysates; Spirulina formulations
Health benefit	Healthy digestive tract construction (such as infectious diarrhoea, antibiotic-associated diarrhoea, and ulcerative colitis); Healthy immune system construction (including preventing allergic disease, decreasing inflammation, and enhancing anti-infection activities)	Treatment of NAFLD, obesity and metabolic syndrome, T2DM and glycaemia, IBS, CKD, dyslipidaemia, PCOS, AD, and inflammation; Prevention of surgical infections and complications, sepsis in infants, and AD; Eradication of Helicobacter pylori	Metabolic health; Satiety; Improved absorption of calcium and other minerals, bone health; Skin health; Digestive tract health; Allergy; Constipation; Immune function in elderly individuals	New antimicrobials; Targeted anti-inflammatory, immunoregulatory, and enhance vaccination efficacy agents; Novel signaling molecules that affect gut pain, sensation, secretion, and motility; Fermented infant formulas and bacterial lysates
Mechanism	Colonization resistance; Normalization of perturbed microbiota; SCFA production; Increased turnover of enterocytes; Regulation of intestinal transit; Competitive exclusion of pathogen; Vitamin synthesis; Bile salt metabolism; Gut barrier reinforcement	Complementary approach combines prebiotic (targets autochthonous beneficial microorganisms) and probiotic; Synergistic approach selects substrate that is utilized by the co-administered live microorganism, enhancing its functionality	Modulation of SCFA production; Promotion of beneficial microbiota; Bile salt metabolism; Alteration of bacterial growth and interaction with immune system; Enhanced secretion of satiety hormones peptide YY and GLP-1; Immunological modulation	Modulation of resident microbiota, immune responses, and systemic metabolic responses; Enhancement of epithelial barrier functions; Regulation of systemic signaling via the nervous system

NAFLD, non-alcoholic fatty liver disease; T2DM, type 2 diabetes mellitus; IBS, irritable bowel syndrome; CKD, chronic kidney disease; PCOS, polycystic ovarian syndrome; AD, atopic dermatitis; SCFA, short-chain fatty acid; GLP-1, glucagon-like peptide1.