Diet rapidly and reproducibly alters the human gut microbiome. Increases in the abundance and activity of Bilophila wadsworthia on the animal-based diet support a link between dietary fat, bile acids and the outgrowth of microorganisms capable of triggering inflammatory bowel disease6
A robust, diverse, gut microbiome may help one keep one’s marbles despite aging:
The human microbiome has important roles in maintaining homeostasis, and disruption of microbial colonization of an infant has systemic effects that may influence health later in life, potentially promoting the development of autoimmunity, allergies, metabolic diseases, and even cancer.
A healthy gut biome can be messed up with antibiotics. Antibiotics strong enough to kill off gut bacteria can also stop the growth of new brain cells in the hippocampus.
In this cross-sectional study, β-diversity, a measure of gut microbial community composition, was statistically significantly associated with all measures of cognitive function.
A healthy gut biome is essential to avoid brain fog.
Studies in two different animals show that proteins made by bacteria harbored in the gut may be an initiating factor in the disease process of Alzheimer’s disease, Parkinson’s disease and ALS.
Extrinsic and intrinsic factors including dietary habits can regulate the composition of the microbiota. Microbes release metabolites and microbiota-derived molecules to further trigger host-derived cytokines and inflammation in the central nervous system, which contribute greatly to the pathogenesis of host brain disorders such as pain, depression, anxiety, autism, Alzheimer’s diseases, Parkinson’s disease, and stroke.
Food patterns and dietary habits result in a change of brain physiology which can be explained by food-derived metabolites (Fig. 2). Metabolites derived from food play important roles in the pathogenesis of brain-related diseases. Recent findings showed the food-derived metabolites include not only SCFAs but also phosphatidylcholine, trimethylamine oxide (TMAO), L-carnitine, glutamate, bile acids, lipids, and vitamins. The food derivatives and microbe-fermented small molecular metabolites are released by gut microbiota into the blood which interacts with the host and further contributes to a variety of disorders, including brain diseases.
The excessive intake of saturated fat and refined carbohydrates is typical of western diet, which also has a negative impact on cognitive functioning since high fat and sugar change intestine bacteria colonies and increase intestinal permeability and lower blood brain barrier. This develops a vulnerability to the influx of toxins from circulation to the brain, which results in cognitive dysfunction.
Shown by a cohort of 89 people between 65 and 85 years of age: certain bacterial products of the intestinal microbiota are correlated with the quantity of amyloid plaques in the brain.
High blood levels of lipopolysaccharides and certain short-chain fatty acids (acetate and valerate) were associated with both large amyloid deposits in the brain. Lipopolysaccharides, a protein located on the membrane of bacteria with pro-inflammatory properties, have been found in amyloid plaques and around vessels in the brains of people with Alzheimer’s disease. Conversely, high levels of another short-chain fatty acid, butyrate, were associated with less amyloid pathology.
Several studies have shown associations between gut microbial measures and neurological outcomes, including cognitive function and dementia. Mechanisms have not been fully established, but there is growing support for a role in microbiota-generated short-chain fatty acids.
Butyrate, a short-chain fatty acid, is increased by a diet rich in high-fiber plant-based foods such as wholegrains, vegetables, fruits, nuts/seeds and legumes. Soluble fiber is prebiotic. It prevents all-cause mortality.