Benefits
Overall distress and cortisol in healthy volunteers (one trial)
In a single 30-day double-blind, placebo-controlled trial in healthy volunteers taking 3 billion CFU daily, scores improved on the overall distress index and on the somatization, depression and anger-hostility scales, the HADS global score improved, and 24-hour urinary cortisol fell. The HADS anxiety subscale did not reach statistical significance (P < 0.06), so an anxiety-specific benefit was not shown. The published report does not say how many people took part, and the trial was run for the manufacturer by contract research organizations.
Calmer behavior in rats (animal study only)
In rats, the same paper reported less anxiety-like behavior in a defensive burying test, which the authors describe only as a screening model for anti-anxiety agents. This is an animal result, not a human one, and it says nothing about how a probiotic compares with prescription medicines.
Re-analysis of the same trial (not a second study)
A second paper by the same group re-analyzed the same 30-day trial and again reported lower distress scores, including among participants whose starting urinary cortisol was low. Because these are the same participants reported a second time, this cannot confirm the first result; it is one trial published twice. The size of that subgroup could not be verified, so no number is given here.
Stress-related GI discomfort
The 2011 paper mentions in passing an earlier study of stress-related digestive discomfort, but that study is not cited anywhere on this page and could not be checked. Treat this as unsupported until the source is provided.
Brain-imaging study of a different formulation
A brain-imaging study sometimes cited here tested a different Lallemand product that contains a third strain (L. plantarum), not this two-strain combination, and that study is not among the references on this page. It should not be counted as evidence for this product.
No published results from the medical-student study
An 8-week study in medical students has been run, but no results have been published. A study with no published outcome is not evidence of any benefit and nothing should be inferred from it.
A null result in adults with low mood
A double-blind randomized placebo-controlled trial in 79 non-medicated adults with at least moderate self-reported low mood (10 dropped out) found no evidence that the formulation improved mood or changed inflammatory and other blood markers. Among those analyzed, similar numbers responded: 9 of 39 on the probiotic and 10 of 38 on placebo. This is a genuine null result and it is reported here as such.
Mechanism of action
GABA signaling (animal work only)
Animal work suggests GABA-related signaling may be involved in the calmer behavior seen in rats. This is a proposed mechanism from animal research only, and no comparison with prescription medicines is justified.
HPA axis cortisol attenuation
In the single 30-day human trial, 24-hour urinary free cortisol fell, which suggests some effect on the body's stress-hormone system. That is one measurement, in one trial, in healthy volunteers.
Vagal afferent signaling
Communication from the gut to the brain along the vagus nerve is one proposed route for probiotic effects on mood. No study cited on this page tested this for these two strains, so treat it as a theory rather than a demonstrated effect.
Short-chain fatty acid production
Gut bacteria can produce short-chain fatty acids that act on the gut lining and on nerve signalling. This is general probiotic theory; short-chain fatty acids were not measured in the studies cited on this page.
Tryptophan / serotonin precursor modulation
Changes in how the gut handles tryptophan could in theory affect the supply of the building blocks of serotonin. This was not measured in the studies cited here.
Gut barrier integrity and reduced systemic inflammation
Probiotics are proposed to help keep the gut lining intact and limit inflammatory molecules passing into the blood. Worth knowing: the one trial with this formulation that actually measured inflammatory blood markers found no change.
Synergistic two-strain combination
The human trial tested the two strains together, so its results cannot be credited to either strain on its own. No study cited here compared the combination against the single strains, so a synergy claim is not supported.
Clinical trials
Clinical evidence on Lactobacillus helveticus R0052 + Bifidobacterium longum R0175 (Probio'Stick® / Cerebiome®) for the indications and outcomes described.
Clinical population described in trial publication.
Messaoudi M et al. 2010 (Br J Nutr 105:755-764, doi:10.1017/S0007114510004319). Double-blind placebo-controlled randomized parallel-group study in healthy volunteers, 30 days at 3×10⁹ CFU/day. Participants were healthy volunteers; the published report does not state how many. Over 30 days the overall distress index (HSCL-90), the somatization, depression and anger-hostility scales, the HADS global score and a coping measure improved, and 24-hour urinary free cortisol fell. The HADS anxiety subscale did not reach statistical significance (P < 0.06). The same paper also includes a separate experiment in rats. The formulation is the manufacturer's own product and the trial was carried out by contract research organizations (the corresponding author is at ETAP-Lab and a co-author is from Biofortis). This is the only reference listed on this page.
Clinical evidence on Lactobacillus helveticus R0052 + Bifidobacterium longum R0175 (Probio'Stick® / Cerebiome®) for the indications and outcomes described.
Clinical population described in trial publication.
Messaoudi M et al. 2011 (Gut Microbes 2(4):256-261, PMID 21983070). This is a further analysis of the same 30-day trial by the same group, not a second trial. It again reports lower HADS and HSCL-90 distress scores, including among participants whose starting urinary cortisol was low. The size of that subgroup could not be verified, and a re-analysis of the same people cannot confirm the original result.
Clinical evidence on Lactobacillus helveticus R0052 + Bifidobacterium longum R0175 (Probio'Stick® / Cerebiome®) for the indications and outcomes described.
Clinical population described in trial publication.
Romijn AR et al. 2017 (Aust N Z J Psychiatry, PMID 28068788). A double-blind randomized placebo-controlled trial in 79 non-medicated adults with at least moderate self-reported low mood, with 10 dropouts. The authors concluded there was no evidence that the formulation is effective for low mood, and no differences in inflammatory or other blood markers. Response rates among those analyzed were similar in both groups: 9 of 39 on the probiotic and 10 of 38 on placebo.