Table 2.

Description of the postbiotics under investigation, their source, the treatment regimen employed, the size of the clinical trial, the targeted condition, and the trial outcomes.

Postbiotic	Microbial Source	Dosage and Regimen	Trial Size	Subject’s  Condition	Outcome
Digestive system
Urolith	Gut microbes	500 and 1000 mg, oral twice daily, 4 months	88	Overweight but absence of any chronic medical	Improved muscle performance postbiotic treated compared to untreated control [124].
Heat-killed	Lacticaseibacillus paracasei *	Lozenges three times a day for 4 weeks	68	Halitosis	Significantly inhibited halitosis and improved oral microbiome [96].
Sodium butyrate	Chemically synthesized	Twice daily orally for 12 weeks	3000	Confirmed IBS patients	Effectively relieved the symptoms of IBS [103].
Heat-treated	Bifidobacterium longum CECT 7347	Once daily orally for 12 weeks	200	Diagnosed with IBS	Reduced IBS symptom severity [105].
Heat-killed and supernatant	Ligilactobacillus salivarius subsp. salicinius AP-32 *, Lacticaseibacillus paracasei ET-66 *, and Lactiplantibacillus plantarum LPL28 *	Oral lozenges thrice for 4 weeks	75	Healthy individuals	Enhanced oral immunity, inhibited oral pathogens, and increased beneficial oral microbiota [95].
2′-linked fucosyllactose	Chemically synthesized	Fed ad libitum orally until week 17	276	Healthy infants	Supported adequate infant growth and was well tolerated [12].
Thermally inactivated	Bifidobacterium animalis subsp. lactis, BPL1	Fed ad libitum orally up to 12 months	217	Healthy infants	Lowered BMI and found to be safe and well tolerated in infants [98].
Fermented formula	LactofidusTM	Oral feeding for 4 weeks	182	Infants diagnosed with uncomplicated regurgitation	Improved symptoms, was well tolerated and safe [99,100].
Fermented formula fraction	LactofidusTM, Bifidobacterium breve C50, and Streptococcus thermophilus 065	Fed ad libitum orally until week 17	200	Healthy infants less than 29 days	Supported infant development and was safe compared to the breastfed group [101].
Oat co-ferment	Lactiplantibacillus plantarum *	Twice-daily enema for 2 weeks	35	Patients diagnosed with moderate to severe IBS	Improved barrier-protective properties in IBS patients [104].
Heat-killed	Lacticaseibacillus paracasei MCC1849 *	Orally once daily for 24 weeks	586	Healthy individuals	Suppressed subjective symptoms in healthy adults [128].
Heat-killed	Lactiplantibacillus plantarum TWK10 *	Twice daily orally for 6 weeks	30	Healthy individuals	Significantly improved endurance [129].
Ferment	Bifidobacterium breve C50 (BbC50) and Streptococcus thermophilus ST065	Ad libitum oral feeding for 6 months	280	Healthy full-term infants	Normal growth, postbiotic was well tolerated, and microbiome composition and metabolic activity were similar to those of breastfed infants [141].
Integument system
Ferment filtrate	Epidermidibacterium Keratini (EPI-7)	Facial application twice daily for 3 weeks	55	Healthy women	Significantly enhanced skin tone and skin microbiome diversity [130].
Yeast extract	Pichia anomala	Facial application twice daily for 8 weeks	110	Healthy women	Enhanced skin barrier-protective function and microbiome composition [131].
Heat-killed	Lacticaseibacillus paracasei, GMNL-653 *	Once- or twice-daily hair wash for 4 months	22	Healthy adults	Improved scalp conditions by controlling sebum secretion and dandruff generation, and promoting hair growth [135].
Lysate	Limosilactobacillus reuteri ATCC-PTA-6475 *	Consumed twice daily for 3 weeks	14	Healthy females following wounding by biopsy	Improved wound repair [127].
Heat-treated	Pediococcus acidilactici LM1013	Dosage information not available	23	Patients diagnosed with acne vulgaris	Inhibited acne vulgaris.
Collagen co-ferment	Lactobacillus acidophilus TYCA06 *, Ligilactobacillus salivarius AP-32, and Bifidobacterium animalis subsp. lactis CP-9	Applied twice daily for 4 weeks	20	Patients diagnosed with acne vulgaris	Ameliorated redness, inflammation, and acne symptoms [132].
Rice-flour co-ferment	Lacticaseibacillus paracasei CBA L74 *	Once daily orally for 12 weeks	50	Infants and kids diagnosed with AD	Not effective in reducing the severity of AD but showed a steroid-sparing effect [133].
Metabolites including lipoteichoic acid, hyaluronic acid, lactic acid, and sphingomyelinase	Lactobacillus plantarum (AN057) *, Lacticaseibacillus casei * (AN177), and Streptococcus thermophilus (AN157)	Twice-daily application on skin for 4 weeks	50	Healthy individuals with no prior skin conditions	Significant beneficial effects on skin, with reduction in wrinkle depth and pore size [134].
Tyndallized extract	Lacticaseibacillus rhamnosus * (IDCC 3201)	Applied twice daily for 12 weeks	100	Infants with diagnosed AD conditions	Improved AD and reduced inflammation [136].
Reproductive system
Ferment	Lacticaseibacillus paracasei * ProSci-92 and L. rhamnosus ProSci-109	Application in deep part of vagina every night for 7 days	50	Diagnosed with bacterial vaginosis (BV)	Ameliorated BV conditions and the symptom [137].
Sensory system
Bacterial lysate	Latilactobacillussakei *	1 drop in each eye every 5 h for 4 weeks	40	Patients with dry eye syndrome	Significantly improved the signs and symptoms of DED and suppressed ocular inflammation [138].
Respiratory system
Complex metabolites	21 kinds of lactobacillus not disclosed	Consumed orally on day 1 of each of the four 3-week treatment cycles	60	Patients confirmed with non-small-cell lung cancer	Attenuated the tumor microenvironment and inflammation [139,140].
Circulatory system
Heat-inactivated	B. animalis subsp. lactis CECT 8145	Daily 50 g ingestion for 12 weeks	120	Abdominally obese individuals	Improved insulin resistance, circulating triglyceride levels, and risk factors for cardiovascular diseases [141].

* The genus name “Lactobacillus” has been amended as per a recent reclassification effort proposed by Zhang et al. [69].