Benefits
Word recall scores in adults with moderate stress
In a 12-week placebo-controlled trial in 129 adults aged 21 to 52 with moderate stress, 10 billion CFU a day improved word recall accuracy more than placebo. A learning test improved only marginally, and six cognitive tests were run without correction for multiple comparisons. Perceived stress, the registered main outcome, fell similarly in both groups. This was one maker-funded trial.
Inflammatory markers during a laboratory stress test
In adults with chronic stress (63 completed) who took HEAL9 or placebo for 4 weeks before a standardized laboratory stress test, plasma soluble fractalkine and CD163, two inflammatory markers, were lower than on placebo. Cortisol and cardiovascular responses to the test did not differ between groups. Two of the authors were employees of Probi, the strain's maker.
Gut inflammation marker in adults over 70
In 66 adults over 70 with raised C-reactive protein (CRP), 10 billion CFU a day for 4 weeks lowered fecal calprotectin, a gut inflammation marker, compared with placebo. CRP, the paper's main outcome, did not differ, nor did zonulin, the outcome first registered for the trial. The same strain with berry powder had no effect, and trail making test scores did not differ from placebo.
Seasonal upper airway comfort (two-strain blend with L. paracasei 8700:2)
These trials tested Probi Defendum, HEAL9 plus L. paracasei 8700:2 (1 billion CFU a day in total), not HEAL9 alone. In 272 adults, fewer caught a cold over 12 weeks (55 vs 67 percent), and in 310 adults colds were shorter. In 898 cold-prone adults the main outcome, cold severity, did not improve, and in 131 day care children cold incidence did not differ.
Spine bone density after menopause (three-strain blend)
HEAL9 is one of three strains in a Probi blend with L. plantarum DSM 15313 and L. paracasei DSM 13434. In a Probi-funded 12-month trial in 249 early postmenopausal women, the blend reduced lumbar spine bone loss versus placebo, but a university-run 12-month trial in 114 women, also funded by Probi, found slightly greater tibia bone density loss on the blend than on placebo.
Mood scores with a SAMe combination product
In a 6-week trial in 90 adults with mild to moderate depressive symptoms, a product combining 200 mg SAMe with 1 billion CFU of HEAL9 lowered self-rated depression scores more than placebo at weeks 2 and 6. Because SAMe was in the same product, the effect cannot be credited to HEAL9, and the trial was small and short.
Mechanism of action
Survival in the gut and attachment to gut lining cells
The authors of the stress and cognition trial state, citing earlier studies, that HEAL9 survives passage through the human digestive tract and attaches to human gut lining cells through a mannose-binding mechanism. This would let it interact with the gut lining, but it does not by itself show any health effect.
Tryptophan metabolism (human marker data)
In the 12-week trial in stressed adults, plasma tryptophan and kynurenine rose on placebo but stayed level on HEAL9, and the rise in tryptophan was significantly larger on placebo. The authors propose a gut-brain pathway, but whether these changes explain the memory test results was not tested.
T-cell signaling (lab research)
In cell culture, cell-free supernatant from L. plantarum DSM 15312 lowered the share of Th1 cells and IL-17 release from CD4+ T cells taken from 30 people with multiple sclerosis. These were laboratory conditions using bacterial products, not people taking the probiotic.
Clinical trials
Randomized, double-blind, placebo-controlled, parallel exploratory trial; one capsule of 10 billion CFU HEAL9 or a maize starch placebo daily for 12 weeks at one site in Cork, Ireland; registered NCT04931082 with perceived stress as the primary outcome; funded by Probi AB, and three of four authors were Probi employees (Önning et al. 2023, Nutrients)
132 adults with moderate stress were randomized and 129 completed (65 HEAL9, 64 placebo); mean age 35, range 21 to 52.
Perceived stress fell 28.3 and 26.6 percent, with no difference between groups, and awakening cortisol fell in both. Word recall accuracy rose on HEAL9 and fell on placebo (p < 0.001), and paired associate learning mean errors improved versus placebo (p = 0.048). Faster reaction times on two other tests were significant only per protocol, and learning test total errors did not differ (p = 0.113). Six cognitive tests were analyzed with no correction for multiple comparisons, cognition was not a listed outcome in the registration, and no sample size calculation was made.
Randomized, double-blind, placebo-controlled trial; HEAL9 or placebo daily for 4 weeks, followed by the Trier Social Stress Test; the abstract does not state the dose; two of seven authors were Probi employees (Önning et al. 2020, Physiol Behav)
70 adults with chronic stress were included and 63 completed (32 HEAL9, 31 placebo).
The stress test affected cardiovascular measures and cortisol, with no difference between groups. Plasma soluble fractalkine and CD163, two inflammatory markers, were significantly lower on HEAL9 than on placebo.
Randomized, double-blind, placebo-controlled three-arm trial; a daily 10 g sachet with 10 billion CFU HEAL9, HEAL9 plus freeze-dried blackberry and black currant powder, or placebo for 4 weeks after a 2-week run-in; registered NCT02342496 with zonulin as the primary outcome, while the paper names CRP; funded by Probi AB, Lund University and Formas, and three authors were Probi employees (Lazou-Ahrén et al. 2025, Probiotics Antimicrob Proteins)
66 adults over 70 with C-reactive protein of 2 to 10 mg/L, 22 per group; all but two in the HEAL9 group completed.
C-reactive protein, the paper's primary outcome, showed only a nonsignificant downward trend on HEAL9 (p = 0.22 versus placebo), and zonulin, the registered primary, did not differ. Fecal calprotectin fell versus placebo (p = 0.03), and fewer HEAL9 users had a calprotectin rise (2 of 17 vs 11 of 22). HEAL9 with berries had no effect on inflammation, and trail making test cognition showed only nonsignificant trends.