Co-administration of a probiotic and vitamin D significantly improved cognitive function in patients with schizophrenia, results from a double-blind randomized controlled trial suggested.
The combination also led to favorable changes in total cholesterol, fasting blood sugar, and a marker of inflammation.
“Targeting the microbiota-gut-brain axis with probiotic and vitamin D might provide a novel approach to promote mental health,” investigators led by Gita Sadighi, MD, Department of Psychiatry, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran, wrote.
The study was published online in Neuropsychopharmacology Reports.
Cognitive Boost
The research includes data on 70 adults with schizophrenia who were on stable antipsychotic medication for at least 6 months. Half took a capsule containing five different probiotic strains plus 400 IU of vitamin D daily for 12 weeks, and half took a matching placebo capsule.
Primary outcomes were disease severity and cognitive function, measured at baseline, every 2 weeks during the trial, and again at the end of the study. Measurement tools included the Positive and Negative Syndrome Scale (PANSS) for disease severity and the 30-point Montreal Cognitive Assessment (MoCA) for cognitive function.
Secondary outcomes were lipid profile, body mass index, gastrointestinal problems, serum C-reactive protein (CRP), and erythrocyte sedimentation rate.
A total of 69 patients completed the trial, and no adverse effects were observed during the study period.
The marginal mean MoCA score increased by 1.96 units in the probiotic/vitamin D group compared with the placebo group during the study period, indicating significant improvement in cognitive function (P = .004).
In addition, the percentage of patients with a MoCA score of ≥ 26 (indicating normal cognition) increased significantly in the supplement group (P = .031), while there were no significant changes in the placebo group (P = .625).
The probiotic/vitamin D supplement was associated with a reduction in the PANSS score by 2.82 units compared with placebo, but the difference between groups was not statistically significant (P = .247).
The supplement group also saw a significant decrease in total cholesterol (P = .011), fasting blood sugar (P = .009), and CRP (P < .001).
Promising ‘Suggestive’ Evidence
Reached for comment, Roger McIntyre, MD, professor of psychiatry and pharmacology and head of the Mood Disorders Psychopharmacology Unit, University of Toronto, Toronto, Ontario, Canada, told this news organization that people living with schizophrenia have “significant impairment in general cognitive functions that can be debilitating and impair quality of life.”
This study provides “suggestive evidence” that the combination of probiotics and vitamin D is safe and effective in the treatment of cognitive dysfunction and “provides hope for persons with the lived experience. However, larger rigorous randomized control trials are needed to confirm these findings,” said Dr. McIntyre, who was not part of the study.
Also weighing in, Christopher M. Palmer, MD, assistant professor of psychiatry at Harvard Medical School in Boston, Massachusetts, noted that many researchers are focusing on the gut-brain connection and its role in a range of neuropsychiatric disorders, including schizophrenia.
“The gut microbiome appears to play a role in a range of factors that can impact brain function, including levels of inflammation, blood sugar, insulin signaling, and neurotransmitter production within the digestive tract,” said Dr. Palmer, who was not involved in the trial. “All of these factors can impact the brain, and in particular, brain metabolism, which increasingly is thought to play a key role in schizophrenia and other neuropsychiatric conditions.”
The new study builds on prior work in important ways, Dr. Palmer added. For example, he noted, earlier research did not show a benefit of probiotics alone.
“One of the challenges with probiotic research is the type of probiotic used. There are single-strain versions and multi-strain versions,” Dr. Palmer said. “This study used a probiotic containing five different bacterial species, so it’s possible that prior studies didn’t use the ideal type of probiotic. Combining the probiotic with vitamin D may also play a critical role.”
The new work replicates findings from a 2019 study in people with schizophrenia who received a four-strain probiotic plus vitamin D or a placebo for 12 weeks, he noted.
“The patients who got the probiotic plus vitamin D experienced improvement in psychiatric symptoms and improvement in three of the same biomarkers used in this study (reductions in total cholesterol, fasting blood sugar, and CRP),” Dr. Palmer said.
Like Dr. McIntyre, Dr. Palmer noted that larger clinical trials are needed before a treatment recommendation can be made.
“We also need to better understand which probiotics to use and the optimal dose of vitamin D supplementation,” he said. “In the meantime, however, patients may want to discuss this research with their clinicians to see if this might be something to consider in their own treatment.”
The study had no funding source. The authors and Dr. McIntyre had no relevant disclosures. Dr. Palmer is the author of the book Brain Energy published by Penguin Random House.
A version of this article appeared on Medscape.com.