If you start reading some of the latest research on human health, you may encounter the terms “gut microbiota” and “gut microbiome” quite a lot. Gut microbiota refers to the trillions of microorganisms that reside in your colon. This microbial community is composed of different strains of bacteria, fungi, single-celled organisms and even viruses. Gut microbiome, on the other hand, is a collective term for the genetic material of your entire gut microbiota. So, what’s the connection to your health?

There isn’t a straightforward answer to that at present. Scientists are only beginning to understand the importance, function and impact of the gut microbiota on human health. According to recent findings, several factors like genetics, diet and disease can influence the state of your microbiome. In turn, your microbiome affects the health and function of major parts of your body, such as your immune system and your central nervous system. In fact, scientists have found intriguing links between your gut microbiome and memory.

At the annual meeting of the American Association for the Advancement of Science (AAAS) in Texas last year, scientist Janet Jansson from Pacific Northwest National Laboratory discussed their previous findings on the relationship between gut microbiome and inflammatory diseases, and how changes in gut microbiota affect the metabolism of fats. They also found that certain gut bacteria – specifically some Lactobacillus species – are linked to genes involved in immune response and inflammatory diseases in humans.

But the highlight of Jansson’s presentation was her team’s latest discovery that introducing different strains of Lactobacillus – a genus of probiotic bacteria believed to be beneficial to overall health – into germ-free mice improves their memory. These inoculated mice also appeared to undergo positive metabolic changes, and comparison of the metabolites in their gut with those of mice without any bacteria allowed Jansson and her team to determine specific metabolites produced by the Lactobacillus species.

Brain imaging also showed that Lactobacillus inoculation increased the concentration of GABA in the hippocampus, the brain region associated with memory. GABA is chemical linked to object recognition memory and working memory. Jansson and her team are currently working on identifying which strain or strains are responsible for this effect.

Gut health and the mind

Jansson’s work supports an earlier literature review from 2014. The team behind it cited numerous studies wherein germ-free animals displayed intensified behaviors in response to external stimuli. The work that begat all others in this vein, namely, a 2004 study from Japan, showed recolonizing the bellies of germ-free mice with a specific species of Bifidobacterium greatly tempered an “exaggerated hypothalamic-pituitary-adrenal axis response to restraint stress.” Other investigations since then have found that exposing germ-free mice to new and unpleasant environments caused them to exhibit behaviors indicative of anxiety and stress. However, introducing gut bacteria or probiotics into these animals reduced and even reversed the behaviors.

As for the effects of the gut microbiome on the human brain, there have been a handful of small-scale studies that suggest a connection. A 2009 study involving patients with chronic fatigue syndrome found that taking a Lactobacillus-containing probiotic could reduce anxiety but not depression.

A more definitive link has been established between gut microbiota and autism spectrum disorder. “Alterations in the communication between the gut microbiome and the brain, including alterations in the composition and metabolic products of the gut microbiome, have been implicated in the complex pathophysiology of [autism spectrum disorder],” said the researchers, noting that germ-free mice have been observed showing lower sociability and deficits in their social cognition abilities. While it’s unlikely that poor gut health is attributable to all cases of autism spectrum disorder, it remains an intriguing possibility.

Sources:

MedicalNewsToday.com

AAAS.Confex.com

EMedicineHealth.com

GeekWire.com

NCBI.NLM.NIH.gov