Yes, Probiotics Can Help the Brain

As many are aware, I’ve spoken and written extensively on the relationship between the gut microbiome and brain health, a relationship that is certainly both complex and multifaceted. This is the central theme of my book, Brain Maker, published way back in 2015.

The gut microbiome is comprised of trillions of microorganisms, including bacteria, viruses, and fungi, which collectively influence not just digestive health but various other aspects of our well-being. In recent years, the “gut-brain axis,” meaning the bidirectional communication between the gut and the brain, has attracted considerable attention for its potential role in neuropsychiatric disorders, cognitive function, and specifically, Alzheimer’s disease.

And as such, we are now witnessing actual interventional trials in which the gut microbiome is manipulated with the hopes of providing a therapeutic benefit, in humans.

We’ll take a look at one such fascinating study further on. But first, here’s an overview of how the gut microbiome connects to brain health and Alzheimer’s disease.

The Gut-Brain Axis

The gut-brain axis facilitates constant communication between the gut and the central nervous system. This communication takes place through multiple pathways, including the nervous system, immune system, endocrine system, and metabolic pathways. Neurotransmitters and signaling molecules produced in the gut can influence brain function, and similarly, the brain can influence the gut through the release of hormones and neural signals.

Gut Microbiome and General Brain Health

A balanced gut microbiome contributes to overall brain health by:

1. Producing Neurotransmitters: Gut bacteria are responsible for the production of neurotransmitters such as serotonin, which plays a vital role in mood regulation and cognitive function.
2. Modulating the Immune System: The gut microbiome can influence the immune response, impacting inflammation, which is a critical factor in various neurological conditions.
3. Affecting the Blood-Brain Barrier: Gut bacteria help maintain the integrity of the blood-brain barrier, protecting the brain from harmful substances.
4. Metabolizing Dietary Compounds: Gut bacteria metabolize dietary components, such as fiber, into short-chain fatty acids, which have neuroprotective effects.

Imbalances in the gut microbiome, known as dysbiosis, have been linked to several neurological disorders, including depression, anxiety, and autism.

Gut Microbiome and Alzheimer’s Disease

The relationship between Alzheimer’s disease and the gut microbiome has been explored in recent studies, revealing several connecting pathways:

1. Inflammation: Dysbiosis can lead to chronic inflammation, a key component in the pathogenesis of Alzheimer’s. The inflammatory molecules may disrupt neural function and contribute to the formation of amyloid-beta plaques, which some consider to be a hallmark of Alzheimer’s disease. For clarification, I do not fully embrace this theory.
2. Metabolic Changes: The gut microbiome affects metabolism, including the metabolism of lipids and glucose. Metabolic dysfunction is a known risk factor for Alzheimer’s disease, and changes in the microbiome may contribute to these metabolic shifts.
3. Alteration of Gut Permeability: Dysbiosis can lead to a “leaky gut,” allowing harmful substances to enter the bloodstream and potentially the brain, contributing to Alzheimer’s disease progression.

With this overview in mind, let’s review the findings of a recent study entitled: The gut microbiome, mild cognitive impairment, and probiotics: A randomized clinical trial in middle-aged and older adults, published in Clinical Nutrition. The study evaluated the cognitive status of 169 adults, aged 52-75 years. The group was the randomized to receive either a probiotic containing a specific strain of bacteria (Lactobacillus rhamnosus GG) or a placebo for a three-month period. All of the participants underwent a deep analysis of the microbial constituents of their intestines at the beginning and the conclusion of the study

The findings of this study are important. First, the researchers demonstrated that certain groups of gut bacteria correlated with lower cognitive function. And before we go any further, it’s worth taking a moment to consider that finding.

Next, the researchers showed that in those participants that were characterized as having mild cognitive impairment (MCI) at the beginning of the study and were in the group that received the probiotic, there was an actual improvement in cognitive function. MCI is generally considered to be an early stage of full-blown Alzheimer’s disease and is a signpost on the road to progressive cognitive decline. So, anything that would halt, or in this case, reverse this decline is worthy of our attention.

The take home message is that probiotics are gaining a foothold in the area of brain health and disease. But in addition, these type of studies reinforce the notion that we need to do everything we can to nurture our gut bacteria as it is clear that the health and function of these organisms plays a central role in charting our health destiny.