Lactoferrin and the immune system

Immune support is the broadest claim made for lactoferrin, and it has a plausible starting point. The protein sits in saliva, tears and mucus, and it is the marker protein of the neutrophil's specific granule. Three pooled analyses have now tested whether swallowing more of it changes infection rates in people. They reached different answers.

Three pooled analyses, six estimates

Pooled odds ratios for lactoferrin supplementation against placebo or no supplement. An odds ratio below 1 favors lactoferrin, and an interval crossing 1 means the analysis could not separate the two.

Why the first two rows disagree

Ali and colleagues searched to March 2021 and pooled six randomized trials into a single figure of 0.57, which reads as a clear reduction. Berthon and colleagues searched to December 2020, a similar window, and split their analysis by age before pooling anything. In adults the odds ratio came out at 1.00, the value that means no difference at all. In infants and children it came out at 0.78.

So the two analyses are not really in conflict about the trials. They disagree about whether to pool children and adults together. Once separated, the reduction sits entirely on the pediatric side.

That distinction carries most of this page, and the pediatric side is not the same intervention. Berthon's own summary states the pediatric finding in terms of formulas containing 35 to 833 mg of lactoferrin a day, which is milk fed to an infant rather than a capsule swallowed by an adult. The adult estimate, on 20 of the 25 studies reviewed, is 1.00.

Ali's analysis also carries a declared competing interest: one author states membership of a scientific advisory board for a lactoferrin supplement product, with no funding received. That is disclosed in the paper rather than discovered, and it does not make the arithmetic wrong. It is a reason to prefer the analysis that separated its populations.

What happened to immune function itself

Berthon's review is the only one of the three that measured immune activity rather than counting infections, and the results do not line up behind the label claim.

• Interleukin-6 fell in adults, by a mean difference of 24.9 pg/mL (95% CI -41.64 to -8.08).
• C-reactive protein did not move: standardized mean difference -0.09 (95% CI -0.82 to 0.65).
• Natural killer cell cytotoxicity did not move: mean difference 4.84 percent (95% CI -3.93 to 13.60).

Natural killer cell activity is the measurement most often invoked when a product is sold as immune support. Pooled across the adult trials that reported it, the interval runs from a 3.93 percent fall to a 13.60 percent rise, which is a measurement compatible with nothing happening.

The narrative counts behind those numbers are mixed in the same way. Eight of 13 adult studies reported a fall in at least one systemic inflammatory marker, 6 of 8 reported some improvement in immune function, but only 2 of 6 found a change in immune cell populations and 2 of 5 a change in immune cell activity.

One internal check on the pooling

Mayorga's 2025 review is the most recent and the only one restricted to children. It found no significant effect on upper respiratory infection, with an interval from 0.27 to 1.40 across eight trials. The same review found significant reductions in diarrhea and in neonatal late-onset sepsis, so the respiratory null is not an underpowered analysis failing to detect anything anywhere.

The diarrhea row is the strongest figure in the table, and it belongs to a separate claim rather than to this one. Fourteen trials at an odds ratio of 0.56 describes what happened to children's bowels. The evidence behind lactoferrin and gut health sets that figure against the Cochrane null on necrotizing enterocolitis and against the single exploratory trial of the adult microbiome.

The sepsis row is the one to treat carefully. A pooled odds ratio of 0.60 for late-onset sepsis does not match the largest single trial ever run on that question: ELFIN randomized 2,203 very preterm infants and reported an adjusted risk ratio of 0.95 (95% CI 0.86 to 1.04). Those two figures describe the same clinical question and point different ways, which is why this site grades infection prevention in preterm infants on the trial rather than on the pool.

Why the grade is Insufficient

Three pooled analyses in four years, and the answer still depends on which one is read and how it grouped its participants. That is the definition of evidence inadequate to settle a question, so the grade is Insufficient rather than Not supported.

Insufficient is not a polite way of saying no. The adult respiratory figure of 1.00 is a real null, and the confidence interval around it still admits a reduction of up to about a quarter, so it does not close the question either. The honest position is that no adequately sized trial has tested immune outcomes in healthy adults as a primary endpoint, and pooling trials that were not designed for it has produced two incompatible answers.

A fourth review makes the same point from the viral side. Sinopoli and colleagues collected 27 records on orally administered lactoferrin across five virus families, found that nine of them were registered protocols rather than results, judged most published trials at high risk of bias, and declined to pool anything. Their stated conclusion is that the effects remain inconsistent.

Where lactoferrin has been tested against a named infection with a trial sized in advance, this reference records the outcome under its own grade: COVID-19 and preterm infection both came back null, while Helicobacter pylori eradication did not. The laboratory case for the protein killing bacteria is separate again and holds up on its own terms, as lactoferrin's antibacterial action sets out. What none of that supports is the general claim, and the full ledger of graded claims about lactoferrin shows how uneven the record is between them.

Nothing here concerns lactoferrin in breast milk, which no trial in these reviews tested and which reaches an infant at concentrations no supplement matches. The page on what lactoferrin does separates the functions by the preparation each was shown in. Doses used in the trials pooled above ran from 35 to 833 mg a day in infant formula and around 200 mg a day in the adult inflammation studies; those are records of what was tested, and the side effects page reports what the same trials logged.