Effects of Bovine Lactoferrin on Vaginal Microbiota in Healthy Postmenopausal Women: A Randomized, Double-Blind, Placebo-Controlled Trial.

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title: "Bovine Lactoferrin and Vaginal Microbiota in Postmenopausal Women: What a Small Trial Found"

description: "A randomized, placebo-controlled trial of 300 mg/day bovine lactoferrin in healthy postmenopausal women. The primary endpoint was not significant, but secondary and exploratory signals are worth watching."

date: "2025"

category: "research-update"

evidenceTier: "C"

studyType: "RCT"

sampleSize: 72

journal: "Nutrients"

pubmedId: "42884644"

TL;DR

In a 12-week, double-blind, placebo-controlled trial of 72 healthy postmenopausal women, bovine lactoferrin at 300 mg/day did not significantly change the overall Nugent score, the primary endpoint. A secondary sub-score and two exploratory markers did move in the hypothesized direction, but these are hypothesis-generating results from a small study. Evidence tier: C (limited, single small RCT with a non-significant primary outcome).

What the Study Found

Lactoferrin is an iron-binding protein found in milk and other secretions, and it has been studied for its effects on immune function and microbial balance. This trial asked whether oral bovine lactoferrin could shift the vaginal microbiota of postmenopausal women, a population in which the balance of vaginal bacteria commonly changes as estrogen declines. The researchers, working with healthy Japanese women, randomized 80 participants to placebo or 300 mg/day of bovine lactoferrin for 12 weeks. Eight were excluded, leaving 72 in the per-protocol analysis (36 per group).

The primary endpoint was the overall Nugent score, a standard microscopy-based measure of vaginal bacterial composition. The score was lower in the lactoferrin group, but the difference did not reach statistical significance. This is the central result, and it is a null finding on the pre-specified primary outcome. Any reading of this study that treats the supplement as having established an effect on vaginal microbiota is not supported by the primary analysis.

Among the secondary endpoints, the Gardnerella/Bacteroides morphotype sub-score was significantly lower in the lactoferrin group than in placebo. The authors describe this as a secondary analysis, and secondary endpoints in a trial of this size carry a higher risk of chance findings, particularly when multiple sub-scores are examined. The result is interesting, but it should be read as a signal, not a confirmed effect.

Two exploratory outcomes also differed between groups. Vaginal immunoglobulin G1 levels were higher in the lactoferrin group, and urinary deoxypyridinoline, a marker of bone resorption, was lower. Exploratory analyses are, by design, not powered to support firm conclusions. The authors themselves frame these findings as hypothesis-generating, and that framing is appropriate. The bone marker result in particular would need dedicated study before anyone draws conclusions about skeletal effects.

Safety data were reassuring within the scope of a 12-week trial. Adverse events were comparable between groups, and no adverse drug reactions were recorded. Twelve weeks and 72 completers are not enough to characterize rare effects or long-term safety.

What This Means for You

The primary result was negative. The overall vaginal microbiota score did not significantly improve with lactoferrin. Do not treat this study as evidence that lactoferrin changes vaginal health.

Secondary and exploratory signals are preliminary. The sub-score and immunoglobulin findings are worth confirming in larger, adequately powered trials before they carry weight.

Context matters. Changes in vaginal microbiota after menopause have many contributors, including estrogen status, hygiene, sexual activity, and antibiotic use. A single supplement trial of this size cannot account for them.

Talk to a clinician about persistent symptoms. Recurrent discharge, odor, irritation, or urinary symptoms warrant medical evaluation rather than self-directed supplementation.

Related habits with broader evidence are better documented for general pelvic and microbial health, such as high-fiber diet and hydration, though neither has been tested specifically against this outcome.

Study Details

Item	Detail
Title	Effects of Bovine Lactoferrin on Vaginal Microbiota in Healthy Postmenopausal Women: A Randomized, Double-Blind, Placebo-Controlled Trial
Study type	Randomized, double-blind, placebo-controlled trial
Population	Healthy Japanese postmenopausal women
Enrolled	80 randomized (40 placebo, 40 lactoferrin)
Analyzed	72 per-protocol (36 per group)
Intervention	Bovine lactoferrin 300 mg/day or placebo
Duration	12 weeks
Primary endpoint	Overall Nugent score (not significant)
Secondary endpoints	Nugent sub-scores (Gardnerella/Bacteroides significantly lower with lactoferrin)
Exploratory outcomes	Vaginal IgG1 (higher with lactoferrin); urinary deoxypyridinoline (lower with lactoferrin)
Adverse events	Comparable between groups; no adverse drug reactions observed
Journal	Nutrients

Sources

1. Study details and abstract: Effects of Bovine Lactoferrin on Vaginal Microbiota in Healthy Postmenopausal Women: A Randomized, Double-Blind, Placebo-Controlled Trial. *Nutrients*. PubMed. https://pubmed.ncbi.nlm.nih.gov/42884644/

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ProtocolEngine provides general health information based on published research. This is not medical advice. Consult a healthcare professional before starting any supplement or health protocol.