New research has found a remarkable connection between diet and brain health.  The key foods are soluble fermentable fiber, and the intermediate is the microbiome in the gut.  An old adage says, “You are what you eat,” but your brain function is also dependent on what your colon bacteria eat – mainly fiber.  The average American consumes less than 12 grams total of fiber per day, while the recommended intake is 20-35 grams.  Evidence shows that the colon bacteria produce several neurotransmitters, including GABA, which lowers anxiety and serotonin, critical for normal mood. In addition to the effect neurotransmitters have on the brain, colonic bacteria produce short-chain fatty acids, the crucial nutrients for brain health.  

Colonic bacteria and the digestive tract

Before we get to the connection between the brain and the microbiome, let’s look at all the good that colon bacteria do for the digestive tract, which is critical for brain health as well. Bacteria in the colon love fiber and produce butyrate and other short-chain fatty acids by digesting and fermenting soluble fiber. (There is a small amount of butyrate in foods such as whole dairy products like butter).  Butyrate provides energy and nourishment for the cells lining the colon (colonocytes), as well as for the bacteria themselves.  The short-chain fatty acids enhance the integrity of the intestinal epithelium, increase mucus production, modulate gut motility, and exert anti-inflammatory effects such as inactivation of nuclear factor kappa B and the promotion of regulatory T cells. Butyrate has been shown to lessen inflammation and pain in IBS (irritable bowel syndrome) and IBD (inflammatory bowel disease), including Crohn’s and ulcerative colitis).

 Another significant effect of fiber and the bacteria that thrive on it is to enhance production of the mucous layer that coats the surface of the cells lining the digestive tract.  Without an adequate mucous layer, non-helpful bacteria in the gut (many of the 10 trillion cells in the gut are not beneficial but are commensal, meaning they coexist with the beneficial bacteria but can cause problems if they become predominant or migrate to the wrong area) are in closer proximity to the wall of the colon, which trigger an inflammatory response that is felt throughout the body.  There is also an increase in intestinal permeability when there is less mucous produced – further increasing inflammation, food allergy, and auto-immune disorders such as ulcerative colitis, rheumatoid arthritis, and thyroiditis. 

Best food-based sources of fiber

There are many forms of fermentable and soluble fiber (including pectins, beta-glucans, guar gum, insulin, and oligofructose), but some of the best food-based sources include:

•  Beans and other legumes-split peas, lentils, etc.  (1 cup provides 1/2 daily requirements of fiber)

• Barley, oats, rye

• Almonds, walnuts, cashews, chia seeds, flax seeds

• Avocados, asparagus, Brussels sprouts, broccoli, cauliflower

• Fruits: green bananas, cherries, prunes, plums, berries, pears

• Fibrous vegetables, sweet potatoes, yams, rutabaga, garlic, onions 

 Broad-based benefits of butyrate

Fiber and butyrate have a significant impact on the health of the gut, but the effects of butyrate go beyond the colon and the microbiota all the way to the brain.  Butyrate has a major effect on gene expression through its function as a histone deacetylase inhibitor (HDAC) leading to gene activation.  This has wide-ranging implications, especially in the brain.  Butyrate can protect brain neurons from cell death in conditions like Parkinson’s disease.  It also has a profound impact on improving memory and learning, especially in toxicity induced dementia, through gene activation as an HDAC inhibitor.  In animal studies focused on injury from toxic metals (which has become a major factor in humans suffering from Alzheimer’s disease), butyrate played a role in cell repair and protection against damage from toxic metals.  In humans, mercury, lead, copper and other metals are implicated in dementia in susceptible patients. 

Butyrate also increases key neurotrophic factors (chemicals that increase brain cell growth) including BDNF, GDNF and NGF.  This improves brain plasticity leading to new neuronal connections and growth and increased cell survival.  In the brain of Alzheimer’s patients there is reduced utilization of glucose for energy, which can predate the onset of the symptoms of dementia by years.  (Many Alzheimer’s patients have depression well before symptoms of memory loss appear that might reflect these early biochemical changes).  One possible way butyrate can affect these brain cells is to provide an alternative energy source as it does for the cells in the colon.  (Studies have shown short-term improvement with the use of ketone sources like MCT oils that create hydroxybutyrate as an energy source). 

Effects of butyrate on the brain

The brain benefits from butyrate in the following ways:

•  An energy source for beta oxidation

• Through upregulation of genes involved with mitochondrial biogenesis (mitochondria are the energy ‘furnaces’ in the neurons that produce ATP, the number and function of these can be increased with butyrate)

• Acetylation of metabolic proteins increasing utilization of glucose

• Protection of neurons from damage induced by inflammation caused by a leaky gut leading to circulation of bacterial cell wall products (LPS) and protecting the blood brain barrier

• Generally reducing systemic inflammation by modifying cytokines

• Enhancing microglia cell maturation (immune cells in CNS)

• Butyrate has anti-depressant effects and modulates neurotransmitters

High fiber diets with soluble fermentable fiber have many other health benefits (diabetes, heart disease, colon cancer, obesity) that are possible because of butyrate production.  Many animal and human studies have shown that increasing fiber and using certain probiotics can enhance butyrate from the colon bacteria.  This has led to better cognitive function in a study in children and lowered anxiety in adults in another study using certain probiotics. 

We are only beginning to appreciate the connection between our microbiome (whose cells and DNA outnumber human cells 10:1) and preventing dementia (and possibly reversing a range of neurological disease, including Alzheimer’s disease and Parkinson’s disease).  Increasing the right types of fiber to give our colon bacteria a chance to produce short-chain fatty acids like butyrate (as well as neurotransmitters while controlling inflammation) is a must to reduce the epidemic of degenerative brain diseases. 

How probiotic supplementation impacts colonic bacteria

Probiotic and prebiotic supplementation can have an impact in resetting the benefits of colonic bacteria.  Ideally, we would maintain a lifelong healthy, diverse, and robust microbiota community.  However, many things can disrupt the health of the microbiota: stress (through the effects of dopamine and norepinephrine), high-fat diets, lack of fermentable fiber, and medications (especially antibiotics).

 Studies on certain probiotics have demonstrated anti-anxiety, anti-depressant, and anti-inflammatory benefits.  In both human and animal studies, species of probiotics including bifidobacter infantis, B pseudocatenulatam, B.longum, lactobacillus brevis, L plantarium, L helviticus have shown benefits in reducing cortisol and improving the function of the HPA (hypothalamic pituitary adrenal axis leading to less anxiety and better ability to cope with stress. In addition, prebiotics like FOS (fructooligosaccharides) and GOS (galacto-oligosaccharides) increase BDNF (brain derived neurotrophic factor that stimulates new neuronal growth), GABA (the calming neurotransmitter) production.  Prebiotics also reduced anxiety and lowered cortisol levels in human studies.  Many of these effects are through the manufacture of butyrate and other SCFAs. 

One more thing to remember about the bacteria in the colon: they are susceptible to the same toxins that are injurious to humans, including exposure to pesticides, antibiotics, hormones and preservatives in food, industrial toxins like PCB and phthalate, heavy metals such as lead and mercury.  In addition, excessive and unnecessary use of oral antibiotics creates havoc in the microbiota.  The truth is we are as dependent on the health of the microbiome as they are on the lifestyle choices we make. It is our choices that impact the health of the microbiota. 

Next-steps: How YOU can improve your gut health

The first step in improving the health of your bacterial friends in the colon is eating a high fiber diet (see the list above for some of the best sources).  Other than fiber intake, eating organic, pesticide free vegetables and animal products, non-toxic fish (like salmon), and reducing environmental exposure to pesticides and other chemicals in the home and workplace will put a big smile on the face of your microbiome. 

If you’d like to learn more about the connection between brain health and a high-fiber diet (or The Adaptation Diet in general), please call us and set up an appointment. Whether you’re interested in living a healthier lifestyle or you’re trying to overcome a chronic condition, we can help you get to your goals.