The gut microbe B. longum may improve the human immune response and help prevent gut disorders. Early evidence suggests that it may also suppress allergies, reduce cholesterol, and improve skin health. Learn more here.
What is Bifidobacterium longum?
Bifidobacterium longum is a Gram-positive, rod-shaped species of bacteria naturally present in the human GI tract. It’s subspecies B. longum subsp. infantis is one of the earliest bacteria to colonize the infant gut. B. longum is often added to food products as a probiotic with various health benefits.
Previously considered separate species, B. infantis and B. suis were shown to be subspecies of B. longum .
Potential Benefits of B. longum
B. longum probiotic supplements have not been approved by the FDA for medical use. Supplements 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.
B. longum ssp. infantis triggered the anti-poliovirus response in a small study of 20 infants .
B. longum ssp. infantis promoted the immune response in human volunteers .
B. longum also stimulated immune function in 45 elderly, hospitalized patients who received an influenza vaccine .
B. longum ssp. infantis had strong immunomodulatory effect in blood drawn from elderly patients, compared with other well-known commercial strains .
B. longum supplementation reduced the incidence of influenza and fever in 27 elderly subjects who received an influenza vaccine .
B. longum fed infants showed a trend toward fewer respiratory tract infections .
B. longum protected mice against pneumonia-induced death by finely tuning the inflammatory response and speeding up lung recovery .
B. longum improved symptoms, reduces mortality and suppresses inflammation in the lower respiratory tract in mice infected with influenza [9, 10].
B. longum ssp. infantis inhibited rotavirus infection in mice .
Oral administration of B. longum protects mice against gut-derived sepsis caused by P. aeruginosa .
B. longum improves survival in mice infected with Salmonella Typhimurium .
B. longum ssp. infantis protects against Salmonella associated injury in mice via a Treg-dependent mechanism [14, 15].
B. longum inhibits the growth of C. albicans and other pathogenic bacteria .
2) Celiac Disease
B. longum ssp. infantis reduced gastrointestinal symptoms in untreated Celiac disease (CD) patients .
B. longum improved gut microbiota composition and immune parameters in children with newly diagnosed CD .
Oral administration of B. longum ameliorated gliadin (gluten)-mediated perturbations in liver iron deposition and mobilization in rats with CD .
B. longum attenuated the production of inflammatory cytokines and the CD4+ T-cell mediated immune response and protects newborn rats against gliadin (gluten)-induced enteropathy .
3) Gut Health
Enterotoxigenic Bacteroides fragilis (ETBF) strains have been suggested to be associated with acute and persistent diarrhea, inflammatory bowel disease and colorectal cancer. B. longum significantly decreased ETBF in humans .
B. longum modulated the intestinal environment and appeared to improve the general health care of elderly patients receiving enteral feeding .
B. longum supplementation elevated biotin levels produced by Bacteroides caccae, and increased Eubacterium rectale, a butyrate producer, in mice .
B. longum maintained high Lactobacilli levels in mice .
B. longum ssp. infantis modulated the gut microbiota and reduces endotoxins in rats .
B. longum ssp. infantis increased propionic, succinic acid, and butyric acid in rats .
Administration of B. longum ssp. infantis significantly reduced the incidence of necrotizing enterocolitis (NEC) and associated inflammation in rats .
B. longum improved colitis in mice .
B. longum ssp. infantis ameliorated colitis in rats  and mice by decreasing Th1 and Th17 responses .
Irritable Bowel Syndrome (IBS)
B. longum ssp. infantis reduced intestinal inflammation and was shown to efficiently treat individual and global IBS symptoms without adverse events .
B. longum ssp. infantis improved abdominal pain/discomfort, bloating/distention, and bowel movement difficulty in patients with IBS .
B. longum ssp. infantis relieved many of the symptoms of IBS in a clinical trial involving women .
B. longum ameliorated ulcerative colitis symptoms in Japanese patients .
B. longum and B. longum subsp. infantis ameliorated ulcerative colitis in mice [24, 34].
B. longum reduced visceral hypersensitivity in mice with IBS .
B. longum ssp. infantis significantly reduced visceral pain threshold pressure of the first pain behavior and total number pain behaviors in rats [36, 37].
Insufficient Evidence For
Researchers are currently investigating whether B. longum 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 B. longum for any reason.
B. longum ssp. infantis reduced proinflammatory markers in patients with ulcerative colitis, chronic fatigue syndrome, and psoriasis .
B. longum reduced inflammation and improved symptoms in patients with ulcerative colitis .
B. longum significantly alleviated inflammation in mice with gout .
B. longum ssp. infantis suppressed proinflammatory IL-17 cytokine production and may be useful in the treatment of Th17-mediated diseases .
Intake of yogurt or powder supplemented with B. longum alleviated subjective symptoms and affected blood markers of allergy in individuals with Japanese cedar pollinosis [42, 43, 44]. Nasal symptoms such as itching, rhinorrhea, and blockage as well as throat symptoms tended to be relieved with this probiotic .
B. longum attenuated allergic airway inflammation  and food allergy symptoms in mice .
Oral administration of B. longum suppressed IgE levels and improved the IgG2a/IgG1 ratio. It also increased Th1 cytokine and decreased Th2 cytokine production in mice .
B. longum balanced the Th1/Th2 response and alleviated β-lactoglobulin allergic inflammation in mice .
Neonatal mother-to-offspring colonization with B. longum reduces allergic responses in mice .
B. longum reduced total cholesterol, particularly among subjects with moderate hypercholesterolemia .
B. longum supplementation significantly reduced total cholesterol, liver lipid deposition, and adipocyte size and positively affected liver and kidney function in hypercholesterolemic rats .
Rats fed a cholesterol-enriched diet supplemented with B. longum had significantly lower triglycerides, LDL-C, very-low-density lipoprotein (VLDL) cholesterol, and MDA [53, 54].
7) Skin Health
B. longum extract, when applied to the skin, was able to improve inflammation parameters, decrease skin sensitivity, increase skin resistance against physical and chemical aggression, and decrease skin dryness in volunteers with sensitive skin .
B. longum exerted photoprotective effects on the skin in mice .
8) Liver Health
B. longum and fructooligosaccharides (FOS) significantly reduced AST, CRP, HOMA-IR, blood endotoxin and steatosis in patients with non-alcoholic steatohepatitis (NASH) .
B. longum and FOS improved biochemical parameters and neuropsychological tests in cirrhotic patients with minimal hepatic encephalopathy (MHE) .
9) Hemodialysis Complications
Oral administration of B. longum decreased serum phosphate levels in 15 patients receiving hemodialysis (HD) .
The administration of B. longum decreased serum concentrations of indoxyl sulfate and P-cresol in a small study of HD patients [60, 61].
In addition, Bifidobacteria produce vitamin B12 and folate, which can normalize serum homocysteine levels in HD patients .
Animal Research (Lacking Evidence)
No clinical evidence supports the use of B. longum 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.
10) Metabolic Syndrome
B. longum improved metabolic parameters in rats on a high-fat diet. This probiotic also reduced metabolic endotoxin concentrations and intestinal inflammation .
11) Cognitive Function
B. longum fed mice exhibited improved learning and memory .
B. longum normalized anxiety-like behavior and hippocampal brain-derived neurotrophic factor (BDNF) in mice with infectious colitis .
Depression can be reversed in rats by administering B. infantis .
Chronic administration of B. infantis protected rats from depressive symptoms caused by stress induced through maternal separation .
Daily administration of B. longum reduced schizophrenic rearing behavior in mice, decreased the resting level of plasma corticosterone and the ratio of kynurenine to tryptophan .
15) Lung Injury
B. longum treatment significantly improved lung injury following infection and sepsis in mice. This probiotic also decreased lung inflammatory responses .
16) Bone Density
B. longum supplementation alleviated bone loss and increased bone formation parameters and bone mass density in ovariectomized rats .
Dietary B. longum significantly inhibited colon and liver and small intestinal tumors in male rats. In female rats, dietary supplementation also suppressed mammary carcinogenesis .
B. longum inhibits colorectal tumors in mice  and rats .
Freeze-dried cultures of B. longum significantly suppressed colon tumor incidence and tumor multiplicity and also reduced tumor volume in rats .
Mechanisms of Effect
Various studies have investigated B. longum’s effect on the cellular level. These may or may not reflect the mechanisms of B. longum probiotics in the human body; however, they may help account for some of the observed effects of these probiotics in human studies.
Under inflammatory conditions, B. longum:
- Decreased Th1-related cytokines (T-bet, IL-2, and IFN-γ) and Th17-related cytokines (IL-12p40, RORγt, IL-17A, IL-21, and IL-23), and increases Treg-related molecules (Foxp3, IL-10, and TGF-β) [29, 73, 40, 41, 3, 27].
- Decreased IL-1α , IL-1β [28, 35, 40], IL-6 [74, 38, 27] and IL-18 .
- Decreased TNF-α expression [28, 39, 38, 27].
- Increased IL-27 .
- Decreased CD80 and CD40 , CXCL1 [40, 27], CRP , iNOS and antimicrobial peptides Reg3b and Reg3g .
In infectious conditions, B. longum:
- Increased natural killer (NK) cell activity [4, 6, 9].
- Increased serum IgA  and decreased IgG2a productions .
- Increased IL-2, IL-12, and IL-18 .
- Decreased IL-6 [9, 10] and IL-8 .
- Decreased TNF-α .
- Both increased  and decreased IL-10 , and decreased [10, 13] and increased IFN-γ .
In allergic conditions, B. longum:
- Decreased IgE and improves the IgG2a/IgG1 ratio [48, 50, 75, 75, 76].
- Increased IgA .
- Increased Th1 cytokine and decreased Th2 cytokine production .
- Decreased IL-4 [75, 46] and IL-5  [a case where IL-5 was increased: 46].
- Increased IL-10 , IL-12 [76, 76] and TGF-β .
- Increased [45, 76] or decreased IFN-γ .
- Suppressed MDC and TARC .
- Increased CD4+CD25+Foxp3+ Treg cells .
In celiac disease, B. longum:
- Decreased TNF-α [18, 20].
- Increased NFκB .
- Increased IL-10 .
- Reduced CD3⁺ T , CD4+ and CD4+/Foxp3+ cells  and increased CD8+ T .
- Increased MIP-1β .
B. longum is considered safe, but should be avoided in immunocompromised individuals, people with organ failure, and dysfunctional gut barrier, where probiotics may lead to infection. To avoid adverse effects, talk to your doctor about whether probiotics could be appropriate for you.