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Fermented foods, microbiota, and mental health: ancient practice meets nutritional psychiatry

Abstract

"The purposeful application of fermentation in food and beverage preparation, as a means to provide palatability, nutritional value, preservative, and medicinal properties, is an ancient practice. Fermented foods and beverages continue to make a significant contribution to the overall patterns of traditional dietary practices. As our knowledge of the human microbiome increases, including its connection to mental health (for example, anxiety and depression), it is becoming increasingly clear that there are untold connections between our resident microbes and many aspects of physiology. Of relevance to this research are new findings concerning the ways in which fermentation alters dietary items pre-consumption, and in turn, the ways in which fermentation-enriched chemicals (for example, lactoferrin, bioactive peptides) and newly formed phytochemicals (for example, unique flavonoids) may act upon our own intestinal microbiota profile. Here, we argue that the consumption of fermented foods may be particularly relevant to the emerging research linking traditional dietary practices and positive mental health. The extent to which traditional dietary items may mitigate inflammation and oxidative stress may be controlled, at least to some degree, by microbiota. It is our contention that properly controlled fermentation may often amplify the specific nutrient and phytochemical content of foods, the ultimate value of which may associated with mental health; furthermore, we also argue that the microbes (for example, Lactobacillus and Bifidobacteria species) associated with fermented foods may also influence brain health via direct and indirect pathways."

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Regulation of Tight Junction Permeability by Intestinal Bacteria and Dietary Components

Abstract

"The human intestinal epithelium is formed by a single layer of epithelial cells that separates the intestinal lumen from the underlying lamina propria. The space between these cells is sealed by tight junctions (TJ), which regulate the permeability of the intestinal barrier. TJ are complex protein structures comprised of transmembrane proteins, which interact with the actin cytoskeleton via plaque proteins. Signaling pathways involved in the assembly, disassembly, and maintenance of TJ are controlled by a number of signaling molecules, such as protein kinase C, mitogen-activated protein kinases, myosin light chain kinase, and Rho GTPases. The intestinal barrier is a complex environment exposed to many dietary components and many commensal bacteria. Studies have shown that the intestinal bacteria target various intracellular pathways, change the expression and distribution of TJ proteins, and thereby regulate intestinal barrier function. The presence of some commensal and probiotic strains leads to an increase in TJ proteins at the cell boundaries and in some cases prevents or reverses the adverse effects of pathogens. Various dietary components are also known to regulate epithelial permeability by modifying expression and localization of TJ proteins."

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High long-term cortisol levels, measured in scalp hair, are associated with a history of cardiovascular disease.

"Abstract

BACKGROUND:

Stress is associated with an increased incidence of cardiovascular disease. The impact of chronic stress on cardiovascular risk has been studied by measuring cortisol in serum and saliva, which are measurements of only 1 time point. These studies yielded inconclusive results. The measurement of cortisol in scalp hair is a novel method that provides the opportunity to measure long-term cortisol exposure. Our aim was to study whether long-term cortisol levels, measured in scalp hair, are associated with cardiovascular diseases.

METHODS:

A group of 283 community-dwelling elderly participants were randomly selected from a large population-based cohort study (median age, 75 y; range, 65-85 y). Cortisol was measured in 3-cm hair segments, corresponding roughly with a period of 3 months. Self-reported data concerning coronary heart disease, stroke, peripheral arterial disease, diabetes mellitus, and other chronic noncardiovascular diseases were collected.

RESULTS:

Hair cortisol levels were significantly lower in women than in men (21.0 vs 26.3 pg/mg hair; P < .001). High hair cortisol levels were associated with an increased cardiovascular risk (odds ratio, 2.7; P = .01) and an increased risk of type 2 diabetes mellitus (odds ratio, 3.2; P = .04). There were no associations between hair cortisol levels and noncardiovascular diseases.

CONCLUSIONS:

Elevated long-term cortisol levels are associated with a history of cardiovascular disease. The increased cardiovascular risk we found is equivalent to the effect of traditional cardiovascular risk factors, suggesting that long-term elevated cortisol may be an important cardiovascular risk factor."

http://www.ncbi.nlm.nih.gov/pubmed/23596141

The metabolic response to ingested glycine.

Abstract

"BACKGROUND:

The metabolic effects of dietary protein are complex. In persons with type 2 diabetes, protein ingestion results in little or no increase in plasma glucose concentrations but a stimulation of insulin and glucagon secretion. Furthermore, when protein is ingested with glucose, a synergistic effect on insulin secretion is observed. The most potent protein is gelatin, which consists of 30% glycine residues.

OBJECTIVE:

The objective of the present study was to determine whether glycine per se stimulates insulin secretion or reduces the glucoseresponse when ingested with glucose.

DESIGN:

Nine healthy subjects were tested on 4 separate occasions. Plasma glucose, insulin, glucagon, and glycine concentrations were measured at various times during a 2-h period after the ingestion of 1 mmol glycine/kg lean body mass, 25 g glucose, 1 mmol glycine/kg lean body mass + 25 g glucose, or water only, given in random order.

RESULTS:

Plasma concentrations of glycine and glucagon were elevated after the ingestion of glycine, as expected. The serum insulin concentration also was slightly elevated after the ingestion of glycine alone. When glycine was ingested with glucose, the plasma glucose area response was attenuated by > 50% compared with the response after the ingestion of glucose alone. The dynamics of the insulin response after the ingestion ofglycine plus glucose were modestly different from those after the ingestion of glucose alone, but the area response was not significantly different.

CONCLUSION:

The data are compatible with the hypothesis that oral glycine stimulates the secretion of a gut hormone that potentiates the effect of insulin on glucose removal from the circulation."

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