L. acidophilus is a common and popular probiotic bacterium. People use it to lower cholesterol, improve gut health, and suppress allergies, but does it work? And what other benefits might it have? Read on to find out.
L. acidophilus is added to commercial yogurts and dairy formulations both for its flavor and for probiotic effect and is one of the most commonly selected Lactobacillus species for dietary use .
L. acidophilus 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.
Iron deficiency was associated with low levels of Lactobacilli in a small study of young women in south India .
L. acidophilus increases iron bioavailability in rats .
In multiple clinical studies, daily consumption of L. acidophilus or a fermented product containing L. acidophilus after each dinner contributed to a significant reduction in cholesterol . However, in another study, L. acidophilus did not lower blood cholesterol in men and women with normal to borderline high cholesterol levels .
L. acidophilus consumption led to a 2.4% to 3.2% reduction in blood cholesterol in clinical studies. Since every 1% reduction in serum cholesterol concentration is associated with an estimated 2% to 3% reduction in risk for coronary heart disease, the authors argued, regular intake of L. acidophilus has the potential to reduce the incidence of coronary heart disease by 6 to 10% .
L. acidophilus protected against atherosclerosis through the inhibition of intestinal cholesterol absorption in mice fed a Western diet .
L. acidophilus reduced cholesterol and inhibited the accumulation of lipoprotein in atherosclerotic plaques in mice .
Healthy volunteers receiving L. acidophilus and cellobiose showed increased levels of Lactobacilli, Bifidobacteria, Collinsella, and Eubacterium, while Dialister was decreased .
L. acidophilus increased the population of Lactobacilli and Bifidobacteria in rats .
L. acidophilus increased Lactobacilli and Bifidobacteria populations, increased levels of acetic, butyric, and propionic acids, and lowered ammonium in a human microbiota simulator .
L. acidophilus administered with amoxicillin/clavulanate was associated with a significant decrease in patient complaints of GI side effects and yeast superinfection .
Other studies show that heat-killed L. acidophilus markedly improved symptoms in patients with chronic diarrhea , L. acidophilus reduced the duration of diarrhea in hospitalized, but not outpatient, children , and ameliorated both rotavirus-positive diarrhea  and nonrotavirus diarrhea in children .
L. acidophilus attenuates diarrhea in mice .
L. acidophilus alleviated the symptoms in patients with perennial allergic rhinitis .
Treatment of patients with bacterial vaginosis with L. acidophilus contributed to the restoration of a normal vaginal environment .
L. acidophilus maintained low pH and increased human vaginal epithelial cell viability .
Daily ingestion of yogurt enriched with L. acidophilus appeared to reduce the incidence of bacterial vaginosis .
Researchers are currently investigating whether L. acidophilus 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. acidophilus for any reason.
L. acidophilus improved blood ammonia and cognitive function in patients with minimal hepatic encephalopathy (MHE). Furthermore, patients who received the probiotic were less likely to develop overt encephalopathy .
Dahi containing L. acidophilus reversed age-related immune function decline in mice .
No clinical evidence supports the use of L. acidophilus 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. acidophilus enhanced natural and acquired immunity in healthy mice .
Both live and non-live L. acidophilus protected against influenza virus (H1N1) infection in mice .
L. acidophilus can effectively prevent bacteria-induced colitis by limiting infection and promoting mucosal protective regulatory immune responses in mice .
L. acidophilus suppressed all of the 74 gram-negative and 16 of the gram-positive bacteria found in burn wounds, which can cause burn wound infections .
L. acidophilus may reduce mutant Streptococcus in dental plaque, and may decrease the cariogenic potential of oral streptococci .
L. acidophilus decreased arthritis symptoms and maintained normal histology of reproductive organs in rats .
L. acidophilus showed effects comparable to the drug indomethacin in decreasing organ damage associated with arthritis in rats. This probiotic down-regulated pro-inflammatory and up-regulated anti-inflammatory cytokines .
Oral administration of L. acidophilus induced the expression of mu-opioid and cannabinoid receptors in intestinal epithelial cells and mediated analgesic function in the gut, similar to the effects of morphine .
L. acidophilus promoted gastric ulcer healing in rats .
L. acidophilus alleviated E. coli infection in mice .
L. acidophilus inhibited the growth of C. difficile, a pathogenic bacterium that causes antibiotic-associated diarrhea  and inhibited the growth of Salmonella enterica in mice, especially when administered after the infection .
L. acidophilus counteracted inflammation in intestinal epithelial cells .
Treatment with L. acidophilus significantly increased butyrate uptake in intestinal epithelial cells. Butyrate plays beneficial roles serving as a primary fuel, ameliorating mucosal inflammation, and stimulating salt absorption .
L. acidophilus had a protective effect on the development of necrotizing enterocolitis (NEC) in rats .
L. acidophilus improved inflammatory and functional aspects of intestinal mucositis caused by chemotherapy in mice .
L. acidophilus reduced intestinal inflammation following infection in newborn mice .
Researchers are currently investigating whether L. acidophilus, as part of the gut flora or taken as a probiotic, could play a role in supporting certain cancer therapies or even in preventing the development of cancer. However, all of this research has been in animals or cells thus far, and there is no clinical evidence to recommend L. acidophilus for this purpose.
Daily oral administration of L. acidophilus suppressed colon tumor incidence, tumor multiplicity, and reduced tumor size in mice .
L. acidophilus reduced tumor volume growth by 50.3 %, reduced the severity of colonic carcinogenesis, and enhanced cancer cell death in mice .
L. acidophilus decreased carcinogenic changes in the colon in rats .
Researchers have conducted a number of cell and animal studies to investigate the effect of L. acidophilus on a biochemical level. Here are some of their findings:
- Enhanced natural killer cell (NK) activity [54, 80].
- Decreased NF-κB [81, 28] and increases IL-8 .
- In influenza, L. acidophilus deotaxin, CSF1, IL-1β, RANTES, and IFN -α in the lung, and increased IL-17 in the intestine .
- Upregulated IL-1α, IL-1β, CCL2, and CCL20, and activated TLR2 in intestinal epithelial cells .
- Increased the secretion of IFNγ from T-cells in fatigued athletes .
- Suppressed Th2-dominant inflammation by activating regulatory T cells and Th1 helper T cells .
- Increased TGF-β [32, 81, 55, 30].
- Decreased NF-κB activity [81, 59].
- Suppressed IL-17 and IL-23 , TNF-α, IL-8, MIR21 [81,59], IL-6, and IL-12 .
- Both increased and decreased IL-12 [55, 30].
- Stimulated IL-10 .
- Induced intestinal IgA .
- Inhibited iNOS and PTGS-2 .
- Suppressee IgE [33, 35], IL-4 [84,85], IL-17A and IL-6 [40,40].
- Increased TGF-β and IgA [84, 40, 40, 41].
- Both increased and decreased IFN-γ [84, 85] and IL-10 [40, 41].
- Increased CD25 and FOXP3  and decreased RORγt .
- Significantly increased CD4(+)CD25(+)Foxp3(+) T cells , decreased the proliferation of CD4(+) T cells stimulated with antigen, and killed antigen-stimulated T cells .
- Improved peritoneal macrophage functions, stimulated NO and IL-6, and inhibited PGE2 .
- Improved lymphocyte functions and stimulated IL-2 .
- Increased catalase (CAT) activity .
- Reversed age-related decline in PPARα, SMP-30, and klotho .
- Altered cytokine production in a tumor into a Th1 protective pattern, favorable to anti-tumor immunity [75, 74].
- Inhibited the expressions of genes involved in tumor angiogenesis and survival, VEGF and HIF-1α .
- Upregulated TIMP-3, HIF-2α, HO-1, and PAI-1 .
- Increased IFN-γ and decreased IL-4 .
L. acidophilus is generally well tolerated. However, the use of probiotics should be avoided in patients with organ failure, immunocompromised status, and dysfunctional gut barrier mechanisms, where it can lead to infections .
To ensure that probiotics are safe for you, and to avoid any adverse effects, talk to your doctor before starting any new probiotic supplements.