Taking a probiotic strain of Bifidobacterium longum reduced physiologic and psychological stress and led to a modest improvement in memory in a small pilot study of healthy men.

The study builds on preclinical studies that identified this B longum strain as a “putative psychobiotic” with beneficial effects on stress-related behaviors, physiology, and cognitive performance in mice, said Gerard Clarke, PhD, from the Alimentary Pharmabiotic Centre, University College Cork, Ireland.

He presented the study findings October 18 during a press briefing at the Society for Neuroscience (SfN) 2015 Annual Meeting.

“The emerging concept of the gut microbiome as a key regulator of brain and behavior represents a paradigm shift in neuroscience. Precise targeting of the microbiome-gut-brain axis with psychobiotics — live microorganisms with a potential mental health benefit — is a novel approach for the management of stress-related conditions,” the study team notes in a meeting abstract.

In the study, 22 healthy male volunteers (mean age, 25.5 years) ingested a capsule containing B longum NCIMB 41676 daily for 4 weeks and a matching placebo capsule for another 4 weeks.

At the start of the study and after 4 weeks of probiotic or placebo, the researchers assessed acute stress (subjective and cortisol output) using the cold pressor test and daily stress using a validated online questionnaire (Cohen Perceived Stress Scale). They assessed cognitive performance using the Cambridge Neuropsychological Test Automated Battery and neurological activity via resting electroencephalography (EEG).

Subtle Benefits

In response to acute stress, B longum NCIMB 41676 led to a reduction in cumulative output of the stress hormone cortisol, as well as a blunted increase in subjective anxiety. On the questionnaire, the men reported being less stressed and anxious while taking the probiotic. They also showed subtle improvement on a visual memory task after receiving the probiotic, as well as altered EEG output.
“These clear but subtle benefits are in line with the predicted impact from preclinical screening platforms and highlight the promise of precision-microbiome manipulation strategies,” the researchers conclude. “Further studies are warranted to evaluate the benefits of this putative psychobiotic in relevant stress-related conditions and to unravel the mechanisms underlying such effects.”

“This study represents a proof of principle,” Dr Clarke said. “The question we are asking now is, can we advance this further and can we use these psychobiotics to deal with the stressors that we encounter on the roller coaster of life, or develop further psychobiotics for patients with stress-related disorders such as depression or anxiety.”

“Today’s findings continue to highlight the importance of the interaction between the gut and the brain,” briefing moderator Robert Yolken, MD, from Johns Hopkins University, Baltimore, Maryland, said in a conference statement. “A better understanding of this link will inform new strategies for preventing and treating many psychological disorders.”

The microbiome is a “very good target” because it can be manipulated, Dr Yolken explained during the briefing.

“It’s very difficult in some ways to change the human genome that we get from our mothers and fathers, but we do have ways of changing the microbiome. We have antibiotics, we have probiotics, and changes in diet will do this as well. This is really a very exciting area because it might allow us to finally do something about these terrible diseases,” Dr Yolken said.

The study was supported by the Science Foundation Ireland, the Health Research Board of Ireland, and the European Community’s Seventh Framework Programme. The authors have disclosed no relevant financial relationships.

Society for Neuroscience (SfN) 2015 Annual Meeting . Abstract 162.04. Presented October 18, 2015.

A new study provides more evidence that following a Mediterranean-type diet (MeDi) is good for the brain.

In a multiethnic cohort of elderly dementia-free adults, those more adherent to the MeDi had larger brain volume than their less adherent peers. And the difference between the groups is equal to about 5 years of aging.

“Our study adds to the existing literature showing that Mediterranean diet is a healthy diet,” Yian Gu, PhD, from Columbia University in New York City, and member of the American Academy of Neurology, told Medscape Medical News.

“These results are exciting, as they raise the possibility that people may potentially prevent brain shrinking and the effects of aging on the brain simply by following a healthy diet,” Dr Gu added in a news release.

The study was published online October 21 in Neurology.

Brain Food

The study involved 674 elderly individuals (mean age, 80.1 years) from the Washington Heights/Hamilton Inwood Columbia Aging Project (WHICAP). They completed food-frequency questionnaires regarding their diet over the past 12 months and underwent high-resolution structural MRI.

According to the diet history, 304 participants had “higher” adherence to the MeDi (they followed the MeDi principles in at least five food components, higher consumption of healthy foods, or lower consumption of unhealthy foods, achieving a MeDi score of 5 to 9) and 370 individuals had “lower” adherence to the MeDi principles (MeDi score, 0 to 4).

The MeDi includes high intake of vegetables, legumes, fruits, cereals, fish, and monounsaturated fatty acids, such as olive oil; low intake of saturated fatty acids, dairy products, meat, and poultry; and mild to moderate amounts of alcohol.

Individuals with higher adherence to the MeDi had total brain volume that was 13.11 mL greater (P = .007) than those with lower adherence. They also had more total gray matter volume (5.0 mL; P = .05) and total white matter volume (6.41 mL; P .05).

In particular, higher fish intake (P = .006) and lower meat intake (P = .002) correlated with greater total gray matter volume. Higher fish intake was also associated with 0.019-mm (P = .03) greater mean cortical thickness, the researchers report.

“The absolute effect of MeDi on brain measures were relatively small,” they note in their article. “However, the magnitude of the effect of consuming at least 5 recommended MeDi food components on TBV [total brain volume] is comparable to that of 5 years of increasing age. Similarly, having fish intake of 3–5 oz at least weekly, or keeping meat intake 100 g daily or less, may also provide a considerable protection against brain atrophy that is equivalent to about 3–4 years of aging,” they point out.

The observed relationships between the MeDi and brain MRI measures were not significantly modified by sex, ethnicity, or APOE ε4 status, they note. They say potential mechanisms include anti-inflammatory and/or antioxidative effects, as well as potential slowing of the accumulation of β-amyloid or phosphorylation and aggregation of tau.

“One More Check Mark” for MeDi

“Our study is an observational study. Although our findings are strong, it is still early to make recommendations based on this single [study]. However, our study provides a strong foundation and rationale for future longitudinal studies and intervention studies,” Dr Gu told Medscape Medical News.

This study is “one more check mark in the positive column for the Mediterranean diet,” Donn Dexter, MD, a neurologist at the Mayo Clinic, Mayo Clinic Health System, Eau Claire, Wisconsin, and member of the American Academy of Neurology, noted in an interview with Medscape Medical News.

“The Mediterranean diet,” he added, “would be a very reasonable thing to do if you are at risk or wanted to actively work on prevention. I encourage my patients to follow that advice. However, I still rank it significantly behind exercise, which has clearly been shown in many more studies to be more beneficial.”

“Overall, the check marks are really starting to add up for lifestyle intervention as being a positive step in prevention and maybe even treatment,” said Dr Dexter, who wasn’t involved in the study.

The study was supported by grants from the National Institutes of Health. Dr Gu has disclosed no relevant financial relationships. Several other authors made disclosure statements, which are listed the original article.

Neurology. Published online October 21, 2015. Abstract