A native gut bacterium sold as commercial strains; the strain, not the species, carries the evidence. Firmest findings: lower artery-clogging cholesterol and easier tolerance of the drug course against a common stomach infection. Bone, gum, mood and blood sugar results conflict; hormone, skin and lifespan claims rest on animals. The cholesterol and workplace trials were company-funded and never independently repeated. (Full Review)

Protocol

Standard maintenance dose

1 × 10⁸ to 1 × 10¹⁰ colony-forming units daily

Trials clustered at 1 × 10⁸ for infection absence, 2 × 10⁹ for cholesterol, 1 × 10¹⁰ for bone.

Strain matched to goal

The strains are not interchangeable

NCIMB 30242 for cholesterol, DSM 17938 with ATCC PTA 5289 for oral endpoints, ATCC PTA 6475 for bone, DSM 17938 alone for constipation and eradication support.

Best time of day

With or just after a meal

Stomach acid is buffered then. Oral-endpoint lozenges dissolve at night after brushing.

Time to effect

Cholesterol effect

6 to 9 weeks

Lipid panel repeats at 12 weeks, covering this window.

Digestive and bowel-frequency changes

1 to 4 weeks

First-week gas and bloating settle within one to two weeks of continued dosing.

Bone signal

12 months

Continuous dosing throughout; rescan no sooner than 12 to 24 months.

Benefits

High: Reduced LDL cholesterol; fewer digestive side effects during Helicobacter pylori eradication

Medium: More frequent bowel movements in chronic constipation; fewer sick-leave days from infections

Low: Periodontal and peri-implant pocket depth; Helicobacter pylori eradication; slower bone loss in older adults; circulating vitamin D; depressive symptoms; blood sugar and insulin handling; bacterial vaginosis cure

Speculative: Lower inflammatory markers in metabolic syndrome; preserved testosterone and testicular size; extended lifespan in model organisms; skin and coat quality

Contraindications

Profound neutropenia (below 500 cells/µL) or blood cancer under treatment

Central venous catheters, ports or prosthetic heart valves

Heart-valve disease with prior infective endocarditis

Short bowel syndrome or D-lactic acidosis

Solid-organ transplant within 6 months of anti-rejection therapy

Critical illness with intensive-care admission

Immune-suppressing drugs (tacrolimus) or chemotherapy during profound neutropenia

Key Interactions

Antibiotics (amoxicillin, clarithromycin)

Proton pump inhibitors (omeprazole)

Antidiarrheals and laxatives (loperamide)

Antifungal and antiprotozoal drugs (fluconazole)

Bile-binding drugs (cholestyramine), statins (atorvastatin)

Cholesterol-lowering supplements (red yeast rice)

Blood-sugar-lowering supplements (berberine)

Fermentable-fibre prebiotics (inulin)

Other interventions (colonoscopy preparation, extended fasting, very-low-carbohydrate diets)

Risk & Side Effects

High: Short-term digestive symptoms

Medium: Increased vaginal discharge

Low: Bloodstream infection in immunocompromised hosts; D-lactic acidosis and brain fogginess with bacterial overgrowth

Speculative: Transferable antibiotic-resistance genes; histamine production by certain strains; long-term immune reprogramming

Monitoring

Marker	Target	Why
LDL cholesterol	Below 100 mg/dL; below 70 mg/dL with known plaque	Primary endpoint of the two positive trials
Apolipoprotein B	Below 80 mg/dL	Counts artery-damaging particles; can stay high when LDL looks acceptable
High-sensitivity C-reactive protein	Below 1.0 mg/L	Tracks the inflammatory pathway this species is proposed to damp
25-hydroxyvitamin D	40 to 60 ng/mL	Rose in the cholesterol trial's secondary analysis
Hemoglobin A1c	4.8% to 5.4%	General metabolic context for a longevity-oriented trial
Urea breath test for Helicobacter pylori	Negative	Confirms whether eradication support worked
Bone mineral density T-score	Above −1.0	Endpoint of the two conflicting bone trials
Gum pocket depth	3 mm or less	Endpoint favored in the dental implant pooling

Cadence: Baseline before the first dose; lipid panel, hs-CRP and vitamin D at 12 weeks; then every 6 to 12 months; bone density no sooner than 12 to 24 months.

Qualitative Assessment

Bowel movement frequency and stool form, logged daily for the first four weeks
Bloating and gas, to separate a settling first week from a persistent problem
Gum bleeding on brushing or flossing
Reflux and upper-abdominal discomfort, particularly with acid-blocking drugs
Energy and cognitive clarity, where the fogginess pattern would surface
Sleep continuity, the number of night-time wakings

Lactobacillus reuteri for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment