L. fermentum is one of the less studied probiotic strains that has shown promise in early clinical studies on cholesterol and immunity. Learn more here.
L. fermentum 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.
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of L. fermentum for any of the below-listed uses. Remember to speak with a doctor before taking probiotic supplements and never use them to replace something your doctor recommends or prescribes.
L. fermentum modestly improved cholesterol in a clinical study of 46 people .
L. fermentum reduced the duration and severity of respiratory illness in highly trained distance runners .
L. fermentum reduced the severity of gastrointestinal and respiratory illness symptoms in male but not female cyclists .
No clinical evidence supports the use of L. fermentum 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. fermentum can reduce inflammation of the upper small intestine in mice .
L. fermentum degrades αS1-casein and lowers the recognition and the binding of this casein to IgE from the blood of patients with cow’s milk allergy .
L. fermentum ameliorates ethanol-induced gastric injury in mice .
L. fermentum enhances the protective effect of Ssanghwa-tang (SHT), a traditional herbal medicine formula, on rat liver .
Oral administration of L. fermentum potentates the immunologic response of an anti-influenza vaccine and may provide enhanced systemic protection by increasing the Th1 response and virus-neutralizing antibodies. The incidence of an influenza-like illness 5 months after vaccination was decreased in the group that consumed this probiotic [31, 32].
L. fermentum suppresses the growth of staphylococci, enterotoxigenic enterobacteria and Candida albicans . It was shown to combat S. aureus and P. aeruginosa, common pathogens in hospital-acquired infections .
L. fermentum inhibits both C. albicans and C. glabrata, the two most common pathogenic yeasts of humans, in the laboratory .
L. fermentum alleviates immunosenescence by enhancing antioxidant enzyme activities and was shown to reduce E. coli infection in aging mice .
Researchers have investigated the potential mechanisms of L. fermentum’s benefits in cell and animal studies. They have found that this probiotic:
- Increased the activity of antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase .
- Increased the IgG2a response over IgG1, indicating a Th1-biased humoral response [32, 41].
- Increased IgA [30, 31, 42], and decreases IgE .
- Increased the proportion of natural killer (NK) cells .
- Increased IFN-γ [32, 41, 30, 5] (a study where it was decreased: ).
- Increased IL-2 [30, 22] and decreased IL-6  and IL-8 .
- Both increased  and decreased IL-4 [41, 30].
- Both increased [38, 39, 26] and decreased IL-10 [41, 30].
- Decreased IL-1β, TNF-α, and iNOS [11, 14, 26 ].
- Decreased Rac, p38, and NF-kappaB activation .
- Increased occludin, EGF, EGFR, VEGF, Fit-1, IκB-α, nNOS, eNOS, Mn-SOD, Cu/Zn-SOD, CAT .
- Increased PGE2 [22, 26].
- Stimulated mucosal immunity, possibly by stimulating tracheal lymphocyte proliferation and increasing lung macrophage population .
- Elevated mineralocorticoid and N-methyl-D-aspartate receptors in the hippocampus after ampicillin treatment .
L. fermentum is commonly found in fermented food products and is considered a “generally recognized as safe” (GRAS) organism by the US FDA . It was found to be safe in infants and children [45, 46].
However, in immunocompromised individuals, it can lead to bacteremia . The use of probiotics in patients with organ failure, immunocompromised status, and dysfunctional gut barrier mechanisms should be avoided.
A strain of L. fermentum AGR1487 causes a pro-inflammatory response in the host and should be avoided .
In order to avoid adverse effects or unexpected interactions, talk to your doctor before using L. fermentum probiotics.