Lactobacillus acidophilus is one of the most common and well-studied probiotic microorganisms. It is a naturally occurring bacteria found in the human intestine and vagina. L. acidophilus has been used for years in fermented foods like yogurt as well as dietary supplements to promote a healthy balance of gut microbiota. In this article, we will explore L. acidophilus in more depth including its health benefits, mechanisms of action and clinical evidence supporting its usage.

What are Probiotics?
Probiotics are live microorganisms that when consumed in adequate amounts confer health benefits. They work by competing with and suppressing the growth of harmful bacteria in the gut. The healthy human gut contains over 100 trillion bacteria belonging to around 1600 different species. A balanced microbiome is crucial for proper digestion, nutrient absorption, immune function and overall well-being. Probiotics help maintain or restore this balance.

L. acidophilus as a Probiotic
L. acidophilus is one of the most widely used probiotic strains. It is a lactic acid producing, anaerobic, non-spore forming, non-motile, gram-positive rod shaped bacteria. L. acidophilus naturally colonizes the human intestines and vagina. Studies show it can survive the harsh acidic environment of the stomach and successfully colonize the gut when consumed orally.

Health Benefits of L. acidophilus
L. Acidophilus imparts many health benefits when ingested regularly as a part of foods or supplements. Some of the major ones are:

Improves Digestion
L. acidophilus enhances digestion by secreting lactase, an enzyme that breaks down lactose in dairy products. It also produces acids like lactic acid to inhibit the growth of harmful bacteria and promote a balanced gut flora for smooth digestion.

Combats Infections
The probiotic properties of L. acidophilus help in fighting intestinal infections caused by pathogens like E. coli, Salmonella, Candida albicans and Helicobacter pylori. It prevents their adhesion to intestinal walls.

Boosts Immunity
Regular intake of L. acidophilus modulates immune response by stimulating the activity of macrophages and lymphocytes. This enhances immunity against infectious agents.

Reduces Cholesterol
Some studies report L. acidophilus may help lower total and LDL cholesterol levels. It binds with bile acids carrying cholesterol from the body. However, results are still inconclusive.

Alleviates Diarrhea
Oral rehydration solutions containing L. acidophilus effectively shorten the duration and reduce frequency of diarrhea. It maintains normal gut flora disrupted due to illnesses.

Lowers Risk of Allergies
Early exposure to probiotic bacteria like L. acidophilus is associated with reduced risks of asthma, eczema and other allergic disorders according to research. But more studies are still required.

Enhances Mood and Behavior
Emerging evidence indicates certain probiotic strains may impact brain function, anxiety, depression and behavior by communicating with gut neurons through the gut-brain axis. However, research on L. acidophilus is still underway.

Mechanisms of Action
L. acidophilus exerts these health effects through several mechanisms:

- Producing antimicrobial compounds called bacteriocins that selectively inhibit pathogenic bacteria.

- Competing with pathogens for nutrition and intestinal epithelial cell adhesion sites, thereby preventing their colonization.

- Stimulating cytokines and immunoglobulins that enhance immune defenses against infections.

- Modulating composition and metabolic activities of indigenous gut microbiota for balanced digestive health.

- Influencing serotonin and GABA levels impacting stress response and mental wellness.

- Assisting absorption of nutrients and minerals like calcium through fermentation and acid production.

Clinical Evidence
Numerous clinical trials have validated the efficacy and safety of L. acidophilus supplementation:

- Studies involving 30-120 participants each have confirmed its ability to treat acute infectious diarrhea within 2-4 days compared to controls.

- Research on 250 subjects linked daily intake of L. acidophilus yogurt to significantly lower total and LDL cholesterol levels over 8-12 weeks versus placebo.

- Double blind trials involving 50-100 subjects established reductions in allergy symptoms like rhinitis with L. acidophilus intake in early childhood versus placebo.

- Several randomized, placebo controlled trials have demonstrated L. acidophilus supplements shorten duration and reduce severity of rotavirus and traveler's diarrhea.

- A review of 18 trials concluded L. acidophilus has clear benefits for upper respiratory tract infections and antibiotic associated diarrhea.

Dosage and Safety
Experts recommend consuming at least 1 billion live L. acidophilus cells per day for benefits. However, products may contain anywhere between 5-30 billion CFU per serving depending on formulation. It is generally well tolerated, but excessive intake could potentially cause gas, bloating or cramps in sensitive individuals. Pregnant and immunocompromised persons should consult a doctor before use. L. acidophilus is considered very safe when taken as directed by reputed manufacturers.

Lactobacillus acidophilus is a valuable resident of the human GI tract and vagina with an established role in promoting intestinal homeostasis, immune function and overall wellness. Regular consumption through fermented foods and dietary supplements provides significant evidence-based health advantages. However, more long term studies are still needed, especially regarding its impact on mood, behavior and chronic illnesses.