L. casei is a beneficial gut microbe that may have probiotic benefits for gut health, stress, immunity, and more. Read on to learn more.
Lactobacillus casei is a Gram-positive, nonpathogenic lactic acid bacterium . It is found in fermented dairy products (e.g. cheese), plant materials (e.g. wine, pickles) and in the reproductive and gastrointestinal tracts of humans and animals [2, 3].
As a nutritional supplement, Lactobacillus casei has been shown to improve intestinal microbial balance, arthritis, type 2 diabetes and to have potential anti-cancer properties .
L. casei 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.
L. casei consumption altered the composition and diversity of human intestinal microbiota. There is a positive correlation between L. casei and Prevotella, Lactobacillus, Faecalibacterium, Propionibacterium, Bifidobacterium and some Bacteroidaceae and Lachnospiraceae, and a negative correlation with the presence of Clostridium, Phascolarctobacterium, Serratia, Enterococcus, Shigella, and Shewanella .
L. casei suppressed potentially harmful Pseudomonas and Acinetobacter in volunteers .
Fermented milk containing L. casei preserved the diversity of the gut microbiota, relieved abdominal dysfunction, and prevented an increase in cortisol levels in healthy medical students exposed to academic stress .
Continuous consumption of fermented milk containing L. casei alleviated constipation-related symptoms, provided satisfactory bowel habits, and resulted in earlier recovery from hemorrhoids in women after childbirth .
A fermented milk beverage containing L. casei relieved irregular bowel movement in gastrectomized patients. It reduced the degree of constipation and improved diarrhea .
L. casei intake was associated with less antibiotic-associated diarrhea in patients [12, 13], reduced the incidence, duration, and severity of diarrhea in children [14, 15], and prevented constipation in mice .
L. casei decreased the severity of intestinal inflammation in mice with inflammatory bowel disease (IBD)  and can counteract the pro-inflammatory effects of E. coli on Crohn’s disease inflamed mucosa by downregulating proinflammatory cytokines .
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of L. casei for any of the below-listed uses. Remember to speak with a doctor before taking L. casei probiotics, and never use them in place of something your doctor recommends or prescribes.
In a study of 47 medical students undertaking an authorized nationwide examination to test their response to stress, L. casei increased serotonin levels, lowered the rate of subjects experiencing common abdominal and cold symptoms and decreased the total number of days students experienced these symptoms .
L. casei promoted the recovery of immunosuppression caused by chemotherapeutic agents in mice, by activating natural killer (NK) cells, cytotoxic T cells and macrophages . These are all white blood cells that recognize and eliminate tumor cells and infected cells.
While some studies found no evidence that consuming L. casei protects against respiratory symptoms , many others have found that L. casei was beneficial in both respiratory and gastrointestinal infections.
L. casei significantly lowered the incidence and duration of upper respiratory tract infections (URTIs) in healthy middle-aged office workers .
Similarly, in healthy shift workers, L. casei decreased the incidence of gastrointestinal and respiratory common infectious disease (CIDs), increased the time to the first occurrence of CID, and reduced the total number of CIDs in the subgroup of smokers. In the course of CID, the total duration of fever was lower and an increase in leukocyte, neutrophil, and natural killer (NK) cell counts and activity was observed .
L. casei also lowered the incidence of common infectious diseases (CIDs) in children , decreased the duration of CID, and especially lessened upper-respiratory-tract infections (URTI) such as rhinopharyngitis in the elderly .
In athletic men and women who engaged in endurance-based physical activities in winter, L. casei lowered the proportion of subjects who experienced 1 or more weeks with upper-respiratory-tract infection (URTI) symptoms and decreased the number of URTI episodes .
Administration of the probiotic L. casei in conjunction with albendazole reduced the Giardia infection and enhanced recovery in mice .
Continuous intake of L. casei contributes to the alleviation of fever caused by norovirus gastroenteritis by correcting the imbalance of the intestinal microflora in the elderly .
Frequent treatment of mice with L. casei induced total protection against infection with Trichinella spiralis parasite worms .
The intake of milk fermented with L. casei during the lactation period modestly contributed to the modulation of the mother’s immunological response after delivery and decreases the incidence of gastrointestinal episodes in the breastfed child .
L. casei improved natural killer (NK) cell activity and produced a more anti-inflammatory cytokine profile in 30 healthy, non-immunocompromised elderly subjects .
L. casei protects mice from anaphylaxis (acute allergic inflammation) and arthritis (autoimmune inflammation) .
L. casei supplementation helped alleviate symptoms and improve inflammatory cytokines in 46 women with rheumatoid arthritis .
L. casei positively contributed to osteoarthritis treatment in rats, by reducing pain, inflammatory responses, and articular cartilage degradation. L. casei together with glucosamine decreased expression of various pro-inflammatory cytokines and matrix metalloproteinases while up-regulating anti-inflammatory cytokines .
Similarly, L. casei effectively suppressed symptoms of rheumatoid arthritis in rats, paw swelling, lymphocyte infiltration and destruction of cartilage tissues. Anti-inflammatory cytokines were increased, while pro-inflammatory cytokines were decreased [43, 44, 45].
Volunteers with seasonal allergic rhinitis treated with L. casei showed a significant reduction in levels of antigen-induced cytokines, showing that probiotic supplementation modulated immune responses in allergic rhinitis and may have the potential to alleviate the severity of symptoms .
L. casei protected mice from acute allergic inflammation (anaphylaxis) .
Following airway allergen administration, mice fed L. casei showed evidence of attenuation of lung inflammation, as well as reductions in proinflammatory cytokines .
Oral administration of L. casei reduced the number of pathogenic (periodontopathic) bacteria in healthy volunteers with mild to moderate gum inflammation (periodontitis) .
L. casei improved insulin sensitivity index in humans, an important risk factor for cardiovascular morbidity, especially stroke and coronary heart disease and mortality  and was shown to reduce cholesterol in laboratory experiments .
A synbiotic blend including L. casei improved fasting blood sugar and insulin in 38 subjects with insulin resistance .
L. casei attenuates the hyperglycemic response to glucose and blood glycerol levels in rats .
L. casei significantly improved glucose intolerance, dyslipidemia, immune-regulatory properties, and oxidative stress in mice with type 2 diabetes .
Cigarette smoking reduces natural killer (NK) activity. L. casei intake prevented the smoke-dependent NK activity reduction in 72 Italian male smokers .
No clinical evidence supports the use of L. casei 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.
An L. casei protein P14 reduced symptoms of atopic dermatitis in mice .
The addition of L. casei to the diet of mice improves survival and resistance against C. albicans infection. This bacterium normalizes the immune response, allowing efficient recruitment and activation of phagocytes, as well as the effective release of pro-inflammatory cytokines .
Even heat-killed L. casei protects immunodeficient mice against C. albicans .
L. casei was effective against H. pylori in laboratory experiments .
L. casei attenuated alcohol-induced liver cell damage in a dish .
In chronic alcohol-induced mice, whey fermented with L. casei significantly attenuated the increased levels of alanine aminotransferase, aspartate aminotransferase, and triglycerides; increased antioxidant activity; and improved liver parameters .
L. casei protects against the onset of non-alcoholic fatty liver disease (NAFLD) in mice , and suppresses nonalcoholic steatohepatitis development, by reducing blood lipopolysaccharide concentrations, suppressing inflammation and fibrosis in the liver, and reducing colon inflammation .
L. casei significantly improved the survival of rats with liver injury, via its anti-oxidative and anti-inflammatory capacities .
In rats with acute liver failure, L. casei inhibits pro-inflammatory cytokines, attenuates hepatic inflammation, prevents intestinal injury and modulates the intestinal microbiota by increasing Lactobacillus and Bifidobacterium levels .
Lactobacillus casei can bind to heterocyclic aromatic amines and can decrease their concentration and their toxicity .
Lactobacillus casei decreases the cytotoxic effects of pesticides on human cells .
Lactobacillus casei supplementation reduces the level of aflatoxin in blood and can improve the adverse effect on body weight and blood parameters in rats .
A fermented milk drink containing Lactobacillus casei may reduce aflatoxin toxicity in humans .
L. casei potentiated the effect of proanthocyanidins extracted from lotus seedpod, ameliorated memory impairment in mice, and improved total antioxidant capacity level .
Consumption of soy isoflavones in combination with L. casei was inversely associated with breast cancer among Japanese women .
L. casei administration significantly reduced the recurrence rate of bladder cancer and colorectal cancer in cancer patients .
In animals, L. casei has demonstrated considerable antitumor activity, mainly by activating macrophages, modulating the host’s immune response and regulating tumor cell death . L. casei exhibits cytotoxic activity against various tumor cells .
L. casei is able to suppress the growth of adult T-cell leukemia cells, acute lymphoblastic leukemia cells and promonocytic leukemia cells .
L. casei decreased cell migration and invasion of colorectal cancer cells [79, 80], inhibited human and mouse colon cancer cell growth, and resulted in an 80% reduction in tumor volume of treated mice .
Administration of milk fermented by L. casei delayed and suppressed tumor growth in mice with breast cancer, both when it was administered preventively and as a treatment. L. casei further reduced tumor vascularity and lung metastasis, and prolonged survival [82, 83, 84].
L. casei decreased breast tumor volume and tumor vascularity in rats .
In cell and animal studies, researchers have observed that L. casei:
- Decreased pro-inflammatory cytokines such as TNF-α, IFN-γ, interleukins IL-2, IL-6, IL-8, IL-17, IL-23, IL-1β [3, 39, 38, 21, 15].
- Increased anti-inflammatory cytokines such as IL-10 [3, 38].
- Inhibited nuclear factor NF-κB .
- May have prevented inflammation in patients who had already synthesized specific IgE or autoantibodies .
Lactobacillus casei is generally well tolerated. The use of probiotics should be avoided in patients with organ failure, immunocompromised status, and dysfunctional gut barrier mechanisms. To avoid adverse effects, talk to your doctor before starting any new probiotic supplements.