Lacticaseibacillus paracasei

An RCT in 82 patients with depression found L. paracasei strain Shirota significantly increased beneficial bacteria (Adlercreutzia, Megasphaera, Veillonella) and decreased bacteria associated with mental illness. Multiple preclinical studies and a review of kefir isolates confirm bifidogenic effects, pathogen reduction, and short-chain fatty acid elevation across various L. paracasei strains.

A double-blind RCT (n=82) found significantly lower IL-6 levels in the L. paracasei Shirota group versus placebo (p<0.05). Animal studies consistently show reduced IL-1β, IL-6, TNF-α, and NF-κB activation in colitis, neuroinflammation, and airway inflammation models across multiple strains (NK112, K47, encapsulated formulations).

In mice, L. paracasei NK112 significantly alleviated E. coli-induced anxiety, depression, and memory impairment, while increasing hippocampal BDNF and reducing neuroinflammatory markers. A human RCT (n=82) of strain Shirota in depressed patients with constipation showed depression scores decreased in both groups but no significant between-group difference, suggesting the effect may not be specific to the probiotic.

In a DSS-induced colitis mouse model, encapsulated L. paracasei biofilm-like microcolonies decreased colonic mucosal injuries and reduced inflammation severity, with lower TNF-α, IL-1β, and IL-17A expression. A review of kefir-derived L. paracasei strains confirms anti-inflammatory and pathogen-adhesion-reducing properties in cell culture models. No human colitis trials identified.

In vitro and mouse studies of L. paracasei M2a demonstrated ~47% uric acid degradation efficiency. In hyperuricemic mice, supplementation significantly improved liver and kidney biomarkers (ALT, AST, BUN, creatinine; p<0.05), reduced inflammatory infiltration, and increased beneficial gut bacteria. No human clinical trials available.

A 9-week double-blind RCT (n=82) of L. paracasei strain Shirota in depressed patients with constipation found no significant between-group difference in total constipation symptom scores. Secondary outcomes showed improvements in rectal tearing/bleeding and stool characteristics favoring the probiotic group, but these did not meet the primary endpoint threshold.

In an OVA-sensitized mouse model, heat-inactivated L. paracasei K47 significantly reduced total IgE, OVA-specific IgE, and OVA-specific IgG1, ameliorated airway hyperresponsiveness, suppressed inflammatory cell accumulation in bronchoalveolar lavage fluid, and rebalanced Th1/Th2 cytokine profiles. No human data available.

A 12-week double-blind RCT (n=80, BMI 23-30) of heat-killed L. paracasei K71 did not reach significance on the primary per-protocol analysis for fat reduction. However, subgroup analysis in participants with stable lifestyles showed significant decreases in subcutaneous fat area, visceral fat volume, body fat percentage, and hip circumference. No adverse events reported.