Limited evidenceGut health

Lactobacillus Fermentum

Sold for cholesterol and immunity, but the direct test of the cholesterol claim was negative. The clearest result for this species is in a niche use: breast pain and mastitis in nursing mothers.

Evidence last reviewed: August 2026

What the science says

Cholesterol lowering Limited evidence
A controlled trial in subjects with elevated cholesterol found that L. fermentum did not meaningfully change serum lipids. This is a direct test of the marketing claim, and it failed.
Breast pain and mastitis in nursing mothers Moderate evidence
A randomized controlled trial found that L. fermentum CECT 5716 reduced Staphylococcus load in breastmilk of mothers with breast pain, and separate randomized work supports its use in preventing lactational mastitis. This applies to one strain in one population.
Sleep quality Limited evidence
A randomized, placebo-controlled trial of heat-treated L. fermentum PS150 reported improved sleep quality, with larger benefits in those with worse baseline sleep. A single trial with a subjective primary outcome.

Dosage & safety

Studied doseTrials used roughly 3–10 billion CFU per day, strain dependent; the CECT 5716 mastitis studies used about 9 billion CFU daily.

SafetyWell tolerated. Standard caution for live probiotics in severely immunocompromised or critically ill people. Mastitis with fever or worsening pain needs medical assessment, not a probiotic alone.

Scientific references

Effect of Lactobacillus fermentum on serum lipids in subjects with elevated serum cholesterol
Simons LA, Amansec SG, Conway P — Nutr Metab Cardiovasc Dis, 2006
Lactobacillus fermentum CECT 5716 Reduces Staphylococcus Load in the Breastmilk of Lactating Mothers Suffering Breast Pain: A Randomized Controlled Trial
Maldonado-Lobón JA, Díaz-López MA, Carputo R, Duarte P, Díaz-Ropero MP, Valero AD, Sañudo A, Sempere L, Ruiz-López MD, Bañuelos Ó, Fonollá J, Olivares Martín M — Breastfeed Med, 2015
Heat-Treated Limosilactobacillus fermentum PS150 Improves Sleep Quality with Severity-Dependent Benefits: A Randomized, Placebo-Controlled Trial
Lee MC, Chen CY, Chen CY, Huang CC — Nutrients, 2025

Where to buy

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