Benefits
Breast pain scores in nursing women
In one maker-run, double-blind trial in women with painful breastfeeding, all three doses lowered breast pain scores versus placebo after 3 weeks, and Staphylococcus counts in breast milk fell from baseline while the placebo group stayed similar. The three doses worked alike, so no dose response was seen.
Breast health in nursing women
A maker-sponsored, double-blind, placebo-controlled trial randomized 625 nursing women to 3 billion CFU or placebo daily for 16 weeks. Among the 291 women who finished, there were 18 mastitis episodes on the strain versus 40 on placebo, but EFSA said no conclusions could be drawn because more than half of the women dropped out and the randomization and analysis had important flaws.
Breast milk bacteria in women under medical care
In a trial of 352 women with a breast infection during lactation, those taking the strain for 3 weeks had lower milk bacterial counts, improved more and had fewer recurrences than women given the antibiotics prescribed by their doctors. There was no placebo group, and the trial does not show that a supplement should replace medical treatment.
Infant formula with the strain from 1 to 6 months
In a double-blind trial of infant formula with this strain from 1 to 6 months of age, babies grew normally and had fewer gastrointestinal infections than babies on standard formula. That evidence is in formula-fed infants, a different population that does not transfer to an adult taking a capsule.
Tolerability in an infant formula trial
The strain was originally isolated from breast milk. In the infant formula safety trial, formula intake and tolerance symptoms did not differ from standard formula. In 2017 EFSA concluded that a cause and effect relationship between this strain and a lower risk of infectious mastitis had not been established.
Mechanism of action
Breast milk origin
The strain was isolated from human breast milk. Its origin is the proposed reason it might suit the mammary environment better than strains from the gut or vagina, but that idea has not been tested directly.
Lower Staphylococcus counts in breast milk
In the breast pain trial, Staphylococcus counts in milk fell from baseline in the probiotic groups, and in the antibiotic-comparison trial milk bacterial counts were lower with the strain. Staphylococci, streptococci and corynebacteria are the main bacteria behind lactational mastitis.
Lactic acid production
Like other lactobacilli, the strain makes lactic acid, which lowers local pH. This is a general proposed mechanism for lactobacilli rather than one measured in the cited trials.
Mammary microbiota balance
Researchers have described painful breastfeeding and mastitis as a mammary dysbiosis, in which potential pathogens increase at the expense of normal milk bacteria. Restoring that balance is the proposed broader mechanism.
Clinical trials
Randomized double-blind placebo-controlled multicentre trial: mothers took one capsule of 3×10⁹ CFU or maltodextrin placebo daily for 16 weeks. Registered as NCT02203877 by the maker, with mastitis incidence as the primary outcome; this report covers infant outcomes. (Pastor-Villaescusa et al. 2020, Benef Microbes)
291 mother-infant pairs who completed the trial (139 probiotic, 152 placebo), out of 625 women randomized.
Infants whose mothers took the strain had a lower incidence of conjunctivitis, and a protective link with respiratory infections depended on Staphylococcus levels in milk and infant stool. The mastitis results were published separately in 2017 and were not posted to the trial registry.
Randomized double-blind controlled trial with four groups: 3×10⁹, 6×10⁹ or 9×10⁹ CFU/day, or maltodextrin placebo, for 3 weeks. Main outcome: Staphylococcus counts in breast milk. (Maldonado-Lobón et al. 2015, Breastfeed Med)
Lactating women with painful breastfeeding.
Staphylococcus counts fell from baseline in the probiotic groups while the placebo group stayed similar, and breast pain scores were lower in each probiotic group than placebo. The three doses had similar effects, so no dose response was seen. The trial was run by the strain's maker.
Randomized trial with three groups: 10⁹ CFU/day of L. fermentum CECT5716, 10⁹ CFU/day of L. salivarius CECT5713, or antibiotics prescribed by primary care, for 3 weeks. No placebo group. (Arroyo et al. 2010, Clin Infect Dis)
352 women with infectious mastitis (124 in the L. fermentum group).
At day 21, milk bacterial counts were lower in the probiotic groups (2.61 and 2.33 log CFU/mL) than in the antibiotic group (3.28). Women in the probiotic groups improved more and had fewer recurrences than those given antibiotics.