L. paracasei is a beneficial probiotic species of bacteria that may benefit the immune system and gut microbiota and reduce allergic symptoms and skin sensitivity. What other potential health benefits could it have? Read on to find out.
Lactobacillus paracasei is a gram-positive lactic acid bacterium, commonly used in dairy products and probiotics. Both L. paracasei and its fermented products are effective immunomodulators, they alleviate allergies, prevent gastric mucosal lesions and inhibit fat tissue accumulation .
L. paracasei probiotic supplements have not been approved by the FDA for medical use and generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
A significant reduction of nasal symptoms and improved quality of life were achieved in patients with Japanese cedar pollinosis, who received L. paracasei when pollen scattering was low. However, the effects were limited during the peak period .
L. paracasei administration to mothers during gestation/lactation protects against airway inflammation in offspring in mice .
Subjects with a medical history of allergic rhinitis to grass pollen that received L. paracasei -fermented milk had lower nasal congestion and nasal itching .
In children with perennial allergic rhinitis, L. paracasei improved symptoms of sneezing, itchy nose, and swollen eyes .
L. paracasei improves the quality of life of subjects with persistent allergic rhinitis who are being treated with an oral H1-antihistamine. In this study, nasal symptoms had not changed, but ocular symptoms had consistently improved .
Heat-killed L. paracasei can effectively improve the overall quality of life for patients with allergic rhinitis induced by house dust mite in human subjects .
Heat-killed L. paracasei improved atopic dermatitis (AD) in adult patients .
According to some researchers, L. paracasei may help reinforce skin barrier function, inhibit water loss, decrease skin sensitivity and modulate the skin immune system leading to the preservation of skin homeostasis .
L. paracasei decreased skin sensitivity and increases barrier function recovery (water retention) in women .
L. paracasei further increased acetic acid and butyric acid, while it decreases ammonia .
L. paracasei supplementation prevented bowel symptom onset in patients on long-term proton pump inhibitors .
L. paracasei, in association with a high-fiber diet, reduced abdominal bloating and prolonged abdominal pain in patients with symptomatic uncomplicated diverticular disease .
L. paracasei modulated intestinal digestion, absorption of nutrients, energy metabolism, lipid synthesis and intestinal protective functions in mice .
Fermented milk with L. paracasei promoted intestinal epithelial cell growth and intestinal epithelial integrity to strengthen the intestinal barrier against chemical and inflammatory stimuli-induced damage .
L. paracasei therapy prevents antibiotic induced visceral hypersensitivity and restores normal gut permeability in rats .
L. paracasei prevented intestinal inflammation in mice with colitis .
Oral supplementation of L. paracasei reduced the clinical progression of necrotizing enterocolitis in infants .
Researchers are currently investigating whether L. paracasei has other health benefits. The potential benefits in this section have produced positive results in at least one clinical trial, but these studies are small, contradictory, or otherwise limited. Talk to your doctor before supplementing with L. paracasei for any reason.
Dietary supplementation with cow’s milk or rice fermented with L. paracasei prevented common infectious disease (CIDs) in children attending daycare .
L. paracasei increases E. coli infection survival in mice .
Both L. paracasei and its supernatant enhance innate immunity through the activation of Toll-like receptor (TLR) signaling .
L. paracasei significantly increases the release of pro-inflammatory cytokines and stimulates the innate immune system in human enterocytes and dendritic cells (DCs) .
However, L. paracasei was not found efficient in 9-year-old children .
L. paracasei, even if heat-killed, inhibits S. mutans and decreases caries lesions in rats .
L. paracasei decreased triacylglycerol in human subjects .
L. paracasei decreased energy/food intake in both human and animal subjects .
Water extract of L. paracasei reduced body weight in obese rats. It decreased the formation of lipid plaques in the aorta, reduced fat cell size and inhibits fat absorption, thereby reducing fat production (lipogenesis) .
In another study, the long-term ingestion of L. paracasei reduced body weight and abdominal fat weight in rats .
L. paracasei decreased body fat in mice .
No clinical evidence supports the use of L. paracasei for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
L. paracasei synbiotic (containing arabinogalactan, fructooligosaccharides) lessened NAFLD progression, lowered inflammatory markers, and reduced the severity of liver injury and insulin resistance in rats .
L. paracasei reduced the adverse effects of Zearalenone (ZEN), an estrogenic toxin produced by numerous Fusarium fungi species in pre- or post-harvest cereals in mice .
L. paracasei prevented urogenital infections by inhibiting Staphylococcus aureus in mice .
A bacteriocin produced by L. paracasei inhibited P. gingivalis, a species of bacteria associated with periodontal disease .
Both viable and nonviable L. paracasei exert the same antiproliferative and proapoptotic effects on gastric and colorectal cancer cells in the laboratory .
L. paracasei significantly inhibits colon cancer cell proliferation .
However, L. paracasei has not been investigated in animals, let alone in humans, so these should not be taken as indicative of any clinical effect. Furthermore, people are often immunocompromised during cancer treatment, so it’s especially important to talk to your doctor before taking probiotics if you are being treated for cancer.
Researchers have conducted a number of cell and animal studies to investigate the effect of L. paracasei on a biochemical level. Here are some of their findings:
- Depending on the experimental setting, L. paracasei had different effects on cytokines.
- It both elevated and suppressed pro-inflammatory cytokines TNF-α [28, 29, 30, 36, 65], decreased [30, 32] or increased IL-1β [36, 65], and inhibited  or elevated IFN-γ [36, 65].
- L. paracasei mostly induced IL-12 [40, 66, 36, 39] [in some studies decreased: 42, 32], and increased the proportion of NK cells , while reducing the Th-2 response [22, 67].
- L. paracasei mostly increased IL-10 [29, 36, 65, 68] [a study where IL-10 is decreased: 42].
- L. paracasei decreased TGF-β1 [42, 22], and increased TGF-β2 .
- L. paracasei increased IL-8 , decreased IL-2, IL-4, IL-5, and IL-13 [36, 4, 8, 54]. and both decreased and increased IL-6 [32, 42].
- L. paracasei increased IgA [65, 68], and decreased IgG4  and IgE .
- L. paracasei stimulated iNOS and NO .
- L. paracasei increased RANTES, IP-10  and ANGPTL4 .
- L. paracasei lowered PPAR-γ [54, 51].
- It decreased MIP-1α , CCL-20 , PTGS2 , COX-2, PGE2 , TLR-4, NOX-4, MCP-1, PPAR-δ , CCAAT/ C/EBPβ, C/EBPα and HR-LPL .
- L. paracasei increased CD4+ T cell and B cell proliferation  and upregulated the CD4+CD25+Foxp3+Treg cell responses .
- It reduced neutrophil infiltration  and attenuated eosinophil influx in the lungs [67, 4, 8].
- L. paracasei increased the expression of almost all TLR signaling genes .
However, the use of probiotics should be avoided in patients with organ failure, immunocompromised status, and dysfunctional gut barrier mechanisms, where L. paracasei can cause infection .
To avoid adverse effects and unexpected interactions, talk to your doctor before starting any new probiotics.