A 12-week postbiotic trial enrolled 121 women. Its main mood result was negative — the hopeful menopause findings came from a subgroup

A double-blind trial published in Nutrients on 31 October 2026 tested a tablet made with heat-killed Lactiplantibacillus plantarum L-137, sometimes described as a postbiotic, in Japanese women aged 45 to 69 who reported everyday stress. Researchers randomly assigned 121 women to 10 mg of the heat-killed bacteria or a dextrin placebo each day for 12 weeks; 119 completed the study.

The cleanest result is also the least exciting. The trial's primary outcome — a standard score of overall negative mood — improved in both groups, but not significantly more with the tablet. Across the full study group, there was also no significant advantage for the total menopausal-symptom score, hot flashes, sleep scores or fatigue. On the main mood score, the placebo group's average change was actually larger: -3.93 points versus -1.83, with p = 0.169 for the difference.

Two laboratory markers did separate the groups. Soluble CD14, which can reflect the body's response to microbial material crossing the gut barrier, rose by an average 51.13 ng/mL with placebo and fell by 36.67 ng/mL with L-137 (p = 0.020). Lactate dehydrogenase, or LDH, rose 4.95 U/L with placebo and fell 2.14 U/L with L-137 (p = 0.010). But neither marker directly measures menopausal relief, and the other intestinal-damage marker tested, FABP2, did not differ. The researchers did not analyse the gut microbiome or directly measure gut permeability.

The intriguing symptom findings came from a prespecified subgroup: 88 women whose starting mood score was at or above the population average. In that subgroup, the hot-flash item improved by 0.52 points with L-137 while worsening by 0.12 with placebo (p = 0.033), and a sleep-maintenance score also favoured the tablet. Those were not the primary outcome, no adjustment was made for the many comparisons, and a second analysis that adjusted for baseline values did not confirm the hot-flash or sleep differences. The authors appropriately call them exploratory.

There is another reason to keep the headline modest. All four authors work for House Wellness Foods, which markets health foods. The company funded and designed the study, supplied the tablets, prepared the manuscript and decided to publish; an outside research organisation collected and analysed the data. That does not make the result false, but independent replication matters especially when the clinical outcomes were mostly negative.

This was not a trial of yogurt or fermented food, and heat-killed bacteria are not the same as live probiotics. It was also not a rigorously staged menopause trial: 65 of the 120 women in the safety analysis were still menstruating, years since menopause were not collected, and efficacy was analysed only in participants who followed the protocol. For now, the study offers a laboratory clue and a hypothesis for another trial, not evidence to replace established care for troublesome hot flashes, poor sleep or mood symptoms.